check engine and reduced engine power problem
Thread Starter
Intermediate
Joined: Mar 2008
Posts: 27
Likes: 0
check engine and reduced engine power problem
Hi guys,
I own a early 2004 C5 (millenium) here in Belgium. It now has 116.000 kms on the clock, about 70.000 miles. All without problems until 7 weeks ago. Suddenly the Check Engine light came on. Local Corvette Performance Center re-set it and said it was a common C5 problem related to a "mis-fire". Same happen 2 weeks later and was again re-set. Then 2 days later whilst in Holland it happened again, followed by Traction Control warning and a Reduced Engine Performance indication. Brought it to the official Corvette importer in Holland. There they searched for 3 weeks to find problem and eventually decided to replace the "TAC Module". Drove the car for 2 weeks and it then happened again. They picked up the car from Belgium, tried to diagnoze it, cleaned up some of the cable connectors, but failed to find the real problem. I picked up the car two days ago and yesterday the same problem occured. Im getting fed up with that. Anybody any sound advice ??
I own a early 2004 C5 (millenium) here in Belgium. It now has 116.000 kms on the clock, about 70.000 miles. All without problems until 7 weeks ago. Suddenly the Check Engine light came on. Local Corvette Performance Center re-set it and said it was a common C5 problem related to a "mis-fire". Same happen 2 weeks later and was again re-set. Then 2 days later whilst in Holland it happened again, followed by Traction Control warning and a Reduced Engine Performance indication. Brought it to the official Corvette importer in Holland. There they searched for 3 weeks to find problem and eventually decided to replace the "TAC Module". Drove the car for 2 weeks and it then happened again. They picked up the car from Belgium, tried to diagnoze it, cleaned up some of the cable connectors, but failed to find the real problem. I picked up the car two days ago and yesterday the same problem occured. Im getting fed up with that. Anybody any sound advice ??
Racer
Joined: Sep 2007
Posts: 251
Likes: 0
From: Las Vegas Nv
Have you done any Mods to the engine/Air intake..etc.I did a cold intake system a couple of weeks ago.A week after install and active handling warming up warning came up for the first time.After driving in a straight line for a while,It came up active handling warm up complete.I have been told the PCM will make adjustments for some mods on the car.3 days ago my check engine light came on for the first time also.Check to see if all connections to the 02 sensors were ok which they were.I have been told Check engine light is for emissions problems only.Check 02 sensor or other emission conponents first.
Thread Starter
Intermediate
Joined: Mar 2008
Posts: 27
Likes: 0
Thanks for your response. No, I have not made any mods. I was just called by the import company / dealer that they have consulted by the US and have decided to replace the Throttle Control unit, as they suspect that to be the problem. That part needs to come from the US so it will take a few days before they get around to exchanging it. Meanwhile I have reset the system and am driving again, but for how long....??
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
You need to display and post here the DTC data when a warning light illuminates. The DTC(s) will help in diagnosing the problem .... go here to learn how to display the data ....
https://www.corvetteforum.com/techti...D=26&TopicID=1
Be certain to post the entire code ... C1234H .... for example.
https://www.corvetteforum.com/techti...D=26&TopicID=1
Be certain to post the entire code ... C1234H .... for example.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Providing us the DTCs will help us get to the ROOT of the issue. Your " Official Corvette Importer in Holland" doesn't have a clue! 
When you experience the problem,,look at the CHECK ENGINE LIGHT (CEL) on the Instrument Cluster and see if it is FLASHING. If it does, that is indicating that your experiencing an Engine Misfire condition. If you check the DTC's during that event (engine running), you may see a P-0300 DTC. Once you shut the engine down, the P-0300 misfire DTC resets and will no longer be displayed until it happens again in that ignition cycle.
Sounds like you have more than one issue. One of your problems could be something as simple as bad plugs and wires.
The engine going into REDUCED ENGINE POWER tells me that your experiencing some sort of issue with the throttle control system. Possibly the TAC, Throttle Position Sensor. Accelerator Peddle Position Sensor or the wires and connections that make up that circuit.
As soon as you read and post your DTCs it will allow us to help you PIN POINT cause of the issue. If you have a LOT of old history DTC's, it will be better if you list all them and then CLEAR all the DTCs and then re-post the ones that display during your problem.
"Replace the Throttle Control Unit"
That will cost you an arm and a leg! 
If anything is wrong it, most likely JUST the Throttle Position Sensor. Thats like a $30 part here in the USA.
Make sure that you tell your service center that you want ALL of your OLD PARTS back. There most likely still good!
Man,,,,I feel bad for all the foreign C5 owners who have to put up with all the BS from service centers that try to use to fix C4, C5 and C6 cars.
Were here for you!
Bill C
Heel & Toe
Joined: Sep 2005
Posts: 16
Likes: 0
i had the same kind of thing happen to my c5.
the fault causeing this was the wireing plugs behind the pannel in the passanger side front inner wheel arch.
liveing in sunny old UK we get alot of rain and i also use a steam cleaner to clean the car.
all the plugs going to the computer behind the plastic inner wheel arch were damp, i disconected the cars 12v battery and then removed all the plugs form the computer, i then used switch cleaner to wash out all the damp ect, gave them a light covering of water resistant switch lube, and replaced every thing, since then it has been perfect.
yours may have a different fault but it may be worth a look.
the fault causeing this was the wireing plugs behind the pannel in the passanger side front inner wheel arch.
liveing in sunny old UK we get alot of rain and i also use a steam cleaner to clean the car.
all the plugs going to the computer behind the plastic inner wheel arch were damp, i disconected the cars 12v battery and then removed all the plugs form the computer, i then used switch cleaner to wash out all the damp ect, gave them a light covering of water resistant switch lube, and replaced every thing, since then it has been perfect.
yours may have a different fault but it may be worth a look.
Thread Starter
Intermediate
Joined: Mar 2008
Posts: 27
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Hi guys, I really feel good about your responses. Here are the codes that I was able to retrieve from the system:
1221 H; 1278 H; 2583 H; U1016 H; U1064 H and U 1096 H.
Yes the throttle control unit that they now say must be replaced (after having the TAC module replaced at a cost of 457 Euro (= $ 680,-) for the part and 911 Euro (=$1360) for labor; is estimated at around 750 Euro (= $1170,-) plus labor ofcourse..... Yep, a Corvette ain't cheap here.. (fuel is 1,50 Euro/litre = around $ 8,10/gallon...) but heay, you only live once. I am about to order a 2008 C6, but MUST get my C5 fixed before I can trade it in...... Many thanks !
1221 H; 1278 H; 2583 H; U1016 H; U1064 H and U 1096 H.
Yes the throttle control unit that they now say must be replaced (after having the TAC module replaced at a cost of 457 Euro (= $ 680,-) for the part and 911 Euro (=$1360) for labor; is estimated at around 750 Euro (= $1170,-) plus labor ofcourse..... Yep, a Corvette ain't cheap here.. (fuel is 1,50 Euro/litre = around $ 8,10/gallon...) but heay, you only live once. I am about to order a 2008 C6, but MUST get my C5 fixed before I can trade it in...... Many thanks !
Intermediate
Joined: Jun 2006
Posts: 32
Likes: 1
From: Stolberg
Hello,i`m loceted near of Aix la chapelle in Germany.
And iff you have any questions about the C5 contact me at info@corvetteproject.de
Greets
werner
And iff you have any questions about the C5 contact me at info@corvetteproject.de
Greets
werner
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Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
Hi guys, I really feel good about your responses. Here are the codes that I was able to retrieve from the system:
1221 H; 1278 H; 2583 H; U1016 H; U1064 H and U 1096 H.
Yes the throttle control unit that they now say must be replaced (after having the TAC module replaced at a cost of 457 Euro (= $ 680,-) for the part and 911 Euro (=$1360) for labor; is estimated at around 750 Euro (= $1170,-) plus labor ofcourse..... Yep, a Corvette ain't cheap here.. (fuel is 1,50 Euro/litre = around $ 8,10/gallon...) but heay, you only live once. I am about to order a 2008 C6, but MUST get my C5 fixed before I can trade it in...... Many thanks !
1221 H; 1278 H; 2583 H; U1016 H; U1064 H and U 1096 H.
Yes the throttle control unit that they now say must be replaced (after having the TAC module replaced at a cost of 457 Euro (= $ 680,-) for the part and 911 Euro (=$1360) for labor; is estimated at around 750 Euro (= $1170,-) plus labor ofcourse..... Yep, a Corvette ain't cheap here.. (fuel is 1,50 Euro/litre = around $ 8,10/gallon...) but heay, you only live once. I am about to order a 2008 C6, but MUST get my C5 fixed before I can trade it in...... Many thanks !
OK, after asking you to post the ENTIRE code ... you post 1221 H ....
There is a P1221, and a C1221 .... the leading character indicates if it is a Powertrain (P) error or a Chassis (C) error ...... VERY different animals ..... I'm gonna assume the 1278 is a Chassis code (C1278) .... and the 2583 ... is that a B2583 (Body) ???
The H at the end of the code can actually be either an H, a C, or both. H means a "History" code ... the problem occured, but is not currently occuring (for some engine and brake system problems the code will go to H status as soon as you turn the engine off). A C means the problem is "Current" .... it is occuring right now. For a handful of codes they can display both an H and a C which basically means that the problem is current, but this isn't the first time it has occured, there is an historic record for it.
Next post .... explanation of what I think you have .....
Last edited by BlackZ06; Mar 18, 2008 at 06:00 PM.
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
The codes starting with a "U" are codes that indicate one computer in the car was unable to communicate with another at a moment in time. These codes are fairly common on a C5 as the data bus is VERY slow by today's standards (about the speed of a dial-up connection) and there is a LOT of data being put on the bus.
Delete the Uxxxx codes for now, they aren't of interest.
The B2583 indicates a problem with the LEFT hand turn signal. As this is a History code DELETE it and we'll attack it later if it comes back ....
The C1278 is set because the Electronic Brake Control Module (EBCM) has the ability to request lowering of engine output (torque) during a Traction Control Event. If the Powertrain Control Module is having problems managing the throttle (controlling torque) it sends a message back to the EBCM saying "I cannot manage torque" and th EBCM then sets this DTC to indicate that Traction Control is not available. Once we fix your P1221 you can delete this code, it should not return.
P1221 .... NEXT POST .....
Delete the Uxxxx codes for now, they aren't of interest.
The B2583 indicates a problem with the LEFT hand turn signal. As this is a History code DELETE it and we'll attack it later if it comes back ....
The C1278 is set because the Electronic Brake Control Module (EBCM) has the ability to request lowering of engine output (torque) during a Traction Control Event. If the Powertrain Control Module is having problems managing the throttle (controlling torque) it sends a message back to the EBCM saying "I cannot manage torque" and th EBCM then sets this DTC to indicate that Traction Control is not available. Once we fix your P1221 you can delete this code, it should not return.
P1221 .... NEXT POST .....
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
The C5 Corvette has a "drive by wire" throttle. In the "old" days the accelerator pedal (that thing your right foot pushes) had a cable from it that went dirrectly to the throttle plate. As you pushed the pedal down the cable moved and opened up the throttle plate.
On a C5 the pedal has no cable to the throttle plate. The pedal has 3 sensors that detect what position the pedal is at .... as you move the pedal, the sensors pick up the change. It has 3 sensors for redundancy/safety reasons .... you wouldn't want just one sensor that suddenly failed and said "FLOOR IT BABY" ..... 
The sensors report the pedal position to the Powertrain Control Module (PCM) which is the computer that actually controls the engine (and transmission if you have an automatic transmission).
The PCM then controls engine performance based not only on how much throttle is requested by the driver, but also on other inputs such as the EBCM requesting lower torque because of a TC event .... If it helps ... think of it this way ..... the driver is REQUESTING certain engine output by pressing down with their right foot .... and the EBCM may be COMMANDING a certain engine output .... the PCM decides what the correct throttle setting should be to meet the various inputs it is receiving.
OK .... class almost over .... the PCM controls the throttle electronically, but it has a "feedback" mechanism that tells the PCM if the throttle plate is actually in the "correct" position as compared to what the PCM requested. Like the accelerator pedal, the PCM does not depend on a single sensor to tell it at what position the throttle plate is actually at ... it uses two sensors to report the plate's position.
The two sensors "oppose" each other. Let's say the throttle is open X percent, and you then step on the accelerator .... as the throttle plate opens one sensor's output should now rise (2 volts to 3 volts) and the other sensor should now drop (from 3 volts to 2 volts) ..... (this is an example ... you get the idea)
The P1221 is set because the PCM sees the two throttle position sensors disagree by more than 7.5 percent.
OK .... so .... my personal advice ..... since you have already replaced the TAC .... either you have a wiring/grounding problem (see Bill Curlee's excellent sticky at the top of this forum on electrical problems) or your PCM is messing up ..... but I'd have to believe the problem is a wiring issue .... if the PCM was failing I'd expect you would see other problems.
On a C5 the pedal has no cable to the throttle plate. The pedal has 3 sensors that detect what position the pedal is at .... as you move the pedal, the sensors pick up the change. It has 3 sensors for redundancy/safety reasons .... you wouldn't want just one sensor that suddenly failed and said "FLOOR IT BABY" .....
The sensors report the pedal position to the Powertrain Control Module (PCM) which is the computer that actually controls the engine (and transmission if you have an automatic transmission).
The PCM then controls engine performance based not only on how much throttle is requested by the driver, but also on other inputs such as the EBCM requesting lower torque because of a TC event .... If it helps ... think of it this way ..... the driver is REQUESTING certain engine output by pressing down with their right foot .... and the EBCM may be COMMANDING a certain engine output .... the PCM decides what the correct throttle setting should be to meet the various inputs it is receiving.
OK .... class almost over .... the PCM controls the throttle electronically, but it has a "feedback" mechanism that tells the PCM if the throttle plate is actually in the "correct" position as compared to what the PCM requested. Like the accelerator pedal, the PCM does not depend on a single sensor to tell it at what position the throttle plate is actually at ... it uses two sensors to report the plate's position.
The two sensors "oppose" each other. Let's say the throttle is open X percent, and you then step on the accelerator .... as the throttle plate opens one sensor's output should now rise (2 volts to 3 volts) and the other sensor should now drop (from 3 volts to 2 volts) ..... (this is an example ... you get the idea)
The P1221 is set because the PCM sees the two throttle position sensors disagree by more than 7.5 percent.
OK .... so .... my personal advice ..... since you have already replaced the TAC .... either you have a wiring/grounding problem (see Bill Curlee's excellent sticky at the top of this forum on electrical problems) or your PCM is messing up ..... but I'd have to believe the problem is a wiring issue .... if the PCM was failing I'd expect you would see other problems.
Burning Brakes
Joined: Jul 2006
Posts: 968
Likes: 12
From: Regina Sask
Since there is no P1221 code on a 2004 Corvette, it would really help to know if it's a Cxxxx code or a Pxxxx code. But a Cxxxx code would turn on the ABS, Service active handling light or Traction Control light/message, and not the check engine light.
It must be either a P1121 (Throttle Position Sensor circuit Sensor circuit intermittent high voltage) or P1122 code (Throttle Position Sensor circuit intermittent low voltage). I would make sure that the throttle blade is not binding and then replace the Throttle Position Sensor.
Or it could be a P2101 to P2135 which ranges from the Throttle Actuator Circuit Range/Performance all the way to the Throttle Pedal Position Sensor.
So without the exact code, it is anyone's guess.
Russ Kemp
It must be either a P1121 (Throttle Position Sensor circuit Sensor circuit intermittent high voltage) or P1122 code (Throttle Position Sensor circuit intermittent low voltage). I would make sure that the throttle blade is not binding and then replace the Throttle Position Sensor.
Or it could be a P2101 to P2135 which ranges from the Throttle Actuator Circuit Range/Performance all the way to the Throttle Pedal Position Sensor.
So without the exact code, it is anyone's guess.
Russ Kemp
Last edited by Russ K; Mar 18, 2008 at 08:21 PM.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
HOLY CRAP! Thats a HELL of a lot of money!!!!!
How locked in are you in getting these parts replaced at that service center??
- Did you pay for the parts in advance?
- Do you have to purchase the parts???
- If you just receive the parts, do you still have to pay anything else??
- With our guidance,,,do you think you can install parts yourself?
- Do you have tools and a volt meter?
- Do you have access to a Factory Service Manual?
- How comfortable are you doing your OWN repairs? (with forum guidance)
Your problems are NOT that extensive and can most likely be corrected easily.
I hope we can save you some money. Please get us the exact codes that your seeing P-XXXX H or C so we can figure out what is happening.
BC
Thats a HELL of a lot of money!!!!! How locked in are you in getting these parts replaced at that service center??
- Did you pay for the parts in advance?
- Do you have to purchase the parts???
- If you just receive the parts, do you still have to pay anything else??
- With our guidance,,,do you think you can install parts yourself?
- Do you have tools and a volt meter?
- Do you have access to a Factory Service Manual?
- How comfortable are you doing your OWN repairs? (with forum guidance)
Your problems are NOT that extensive and can most likely be corrected easily.
I hope we can save you some money. Please get us the exact codes that your seeing P-XXXX H or C so we can figure out what is happening.
BC
Thread Starter
Intermediate
Joined: Mar 2008
Posts: 27
Likes: 0
Hi Guys, you can not start to believe how grateful I am for your immediate and extensive reactions ! You're all top-class !
I'd like to thank especially BlackZ06 for his explanations ! So it all seems to focus on the 1221H code. I have looked at it again and it is a P1221H code on page 10PCM, so related to the Powertrain Control Module.
In response to the last questions, no I am not confident enough to start working on the engine myself... unless it is cleaning the wiring and making sure it's damp-proof.
Again, I sincerely appreciate you advice and suggestions !!!
I'd like to thank especially BlackZ06 for his explanations ! So it all seems to focus on the 1221H code. I have looked at it again and it is a P1221H code on page 10PCM, so related to the Powertrain Control Module.
In response to the last questions, no I am not confident enough to start working on the engine myself... unless it is cleaning the wiring and making sure it's damp-proof.
Again, I sincerely appreciate you advice and suggestions !!!
Burning Brakes
Joined: Jul 2006
Posts: 968
Likes: 12
From: Regina Sask
Since code P1221 is not listed for a 2004 C5, I looked it up for a 2003. And it is to do with the throttle position sensor that is on the passenger side of the throttle body. There are detailed tests for this sensor. But I would just install a new one. The sensor is very easy to replace.
Russ Kemp
Russ Kemp
Thread Starter
Intermediate
Joined: Mar 2008
Posts: 27
Likes: 0
Russ, by the way, you're right. I have a 2003 model that was delivered to me and first registered in March 2004. (we are running a bit behind here in Europe.... the 2008 model is just released here some 3 weeks ago)
Lex
Lex
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
The Throttle Position Sensor is GM Part number is 17113566 ... GM list price for the part in the US is $133.49 but you can get it for much less from forum supporting vendors ... though they may charge extra for international shipping.
http://www.gmpartsdirect.com
http://www.gmpartshouse.com
http://www.gmpartsdirect.com
http://www.gmpartshouse.com
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
LEX
Gene Culley at www.gmpartshouse.com will give you that part at a discount:
Item Number MSRP Core Price Price
17113566 $133.49 $0.00 $86.76
Electrical - Powertrain control - Throttle position sensor
Throttle position sensor, corvette 1997 - 2004
I believe that he also ships to other countries. Contact him for details. He is a very trusted parts dealer!
That part is very easy to replace and you should be able to carry out the repairs easily. Remove two small torx screws and disconnect one connector. Remove the old sensor and install the new one. Your DONE.
DTC P1221
Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5 volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensors, this DTC will set and the Reduced Engine Power message will be displayed.
Conditions for Running the DTC
DTCs P1517, or P1518 are not set.
The ignition switch is in the crank or run position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
TP sensor 2 disagrees with TP sensor 1 by more than 7.5 percent.
All above conditions are present for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
Bill C
Gene Culley at www.gmpartshouse.com will give you that part at a discount:
Item Number MSRP Core Price Price
17113566 $133.49 $0.00 $86.76
Electrical - Powertrain control - Throttle position sensor
Throttle position sensor, corvette 1997 - 2004
I believe that he also ships to other countries. Contact him for details. He is a very trusted parts dealer!
That part is very easy to replace and you should be able to carry out the repairs easily. Remove two small torx screws and disconnect one connector. Remove the old sensor and install the new one. Your DONE.
DTC P1221
Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5 volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensors, this DTC will set and the Reduced Engine Power message will be displayed.
Conditions for Running the DTC
DTCs P1517, or P1518 are not set.
The ignition switch is in the crank or run position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
TP sensor 2 disagrees with TP sensor 1 by more than 7.5 percent.
All above conditions are present for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
Bill C
Thread Starter
Intermediate
Joined: Mar 2008
Posts: 27
Likes: 0
Hi guys, you're all top-class ! First of all Happy Easter to you !
I have, ever since having re-set the codes a few days ago, driven the car for about 800 miles without problems, until I visited the nearby Corvette dealer to have a look at the 2008 model...Great car !
When driving home afterwards, the engine went up to 1200 rpm and got stuck there, irrespective of the position of the throttle pedal... So I really had to "nurse" the car back home.
I have just read the codes and these are:
10 PCM P1221H and P1515H
28 TCS C1278H.
No other codes.
Do these codes confirm the asssessment you have come to earlier ???
Again, I really appreciate your support, you're a good bunch !
Thanks
Lex
First of all Happy Easter to you ! I have, ever since having re-set the codes a few days ago, driven the car for about 800 miles without problems, until I visited the nearby Corvette dealer to have a look at the 2008 model...Great car !
When driving home afterwards, the engine went up to 1200 rpm and got stuck there, irrespective of the position of the throttle pedal... So I really had to "nurse" the car back home.I have just read the codes and these are:
10 PCM P1221H and P1515H
28 TCS C1278H.
No other codes.
Do these codes confirm the asssessment you have come to earlier ???
Again, I really appreciate your support, you're a good bunch !
Thanks
Lex