Reduced Engine Power / Service Traction System - P2135 & C0242
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Reduced Engine Power / Service Traction System - P2135 & C0242
While cruising yesterday, I was in 5th gear around ~65mph and went up to 1/3 to 1/2 throotle to pass someone when all the sudden the car fell on its face, got a check engine light that came on and on the DIC - Reduced Engine Power & Service Traction System.
Limped the car home, but it seemed to run fine. Just that is limited any power... Got a scanner on it today & came up with the following codes:
I cleared the codes and took it for a short ~5 mile ride. Codes havent came back yet! But im still concerned there may be an issue that will re-arise...
I searched the codes, but didnt find any clear cut answers...
Some about the Throttle Body needing replacement and the other codes being a result of the TB issue.
Another being the pedal assembly needing replacement, but still other codes just caused by the p2135.
Anyone have any ideas, known TSBs or recalls, etc??
Thanks a lot!
Chris
PS - its worth mentioning, the car has headers, cam, ported TB & IM, vararam cai, and comp cam 235/243 .620/.623 114+1...
Limped the car home, but it seemed to run fine. Just that is limited any power... Got a scanner on it today & came up with the following codes:
- C0242 - Powertrain Control Module Indicated Traction Control System Malfunction
- P2135 - Throttle / Pedal Position Sensor/Switch A/B Voltage Correlation
I cleared the codes and took it for a short ~5 mile ride. Codes havent came back yet! But im still concerned there may be an issue that will re-arise...
I searched the codes, but didnt find any clear cut answers...
Some about the Throttle Body needing replacement and the other codes being a result of the TB issue.
Another being the pedal assembly needing replacement, but still other codes just caused by the p2135.
Anyone have any ideas, known TSBs or recalls, etc??
Thanks a lot!
Chris
PS - its worth mentioning, the car has headers, cam, ported TB & IM, vararam cai, and comp cam 235/243 .620/.623 114+1...
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
TTT - Happened again tonight, this time ran rough as heck when the CEL came back.... Cleared codes again and it runs fine... any ideas?
Realized after fact I shoulda left codes in there to bring to dealer!
Realized after fact I shoulda left codes in there to bring to dealer!
Team Owner
Joined: Sep 2005
Posts: 20,352
Likes: 568
From: Ventura County, Calif
Pretty common malfunction......Accelerator Pedal Position Sensor. It usually shows up as P2138 but......I think 2135 is just the other half.
The fix usually involves getting a new accelerator pedal assembly.
However, a few members have reported success getting down there at the pedal and checking the connector. A few have been found loose and simply taking the connector off, checking it for damaged pins and cleanliness and plugging it back in securely solved the problem. But again, the vast majority of cases need a new pedal assy.
Then there was this case that probably doesn't apply to you but who knows?
http://forums.corvetteforum.com/c6-c...this-time.html
Good luck.
The fix usually involves getting a new accelerator pedal assembly.
However, a few members have reported success getting down there at the pedal and checking the connector. A few have been found loose and simply taking the connector off, checking it for damaged pins and cleanliness and plugging it back in securely solved the problem. But again, the vast majority of cases need a new pedal assy.
Then there was this case that probably doesn't apply to you but who knows?
http://forums.corvetteforum.com/c6-c...this-time.html
Good luck.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
P2135 is the TPS sensor A B correlation. If either sensor is out of wack with the other sensor, P2135 sets and will cause the PCM to go into reduced power mode. There are two TPS sensors within the throttle body, both have to send the appropriate signal to the PCM, TPS sensor 1 has a range of .35v to 4.75 while sensor 2 has a range of 4.65 to .35v. So as sensor 1 is increasing in voltage as the throttle is opened, sensor 2 is reducing voltage by the same amount. If the correlation between these two sensors is out of spec the PCM deems that an error in the TB has occurred so the PCM then sets the DTC and disables the TAC system and goes into reduced power mode.
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Rick T... Thanks for the info, I will definitely get under the dash today and look at those connectors before going any further, but figure on just getting a new pedal anyway
tjwong... thanks for the explanation! Amazing how advanced these things are!
I got a PM from ChevyDave and he linked me to a blow-up of the pedal assy and to gmpartshouse for a new pedal assy. Only $75, and I thought this would be something costing hundreds so was going to try for it under warranty, but at that cheap its not worth arguing with dealer, who will probably say its the TB since its ported out or the cars tuned, etc...
tjwong... thanks for the explanation! Amazing how advanced these things are!
I got a PM from ChevyDave and he linked me to a blow-up of the pedal assy and to gmpartshouse for a new pedal assy. Only $75, and I thought this would be something costing hundreds so was going to try for it under warranty, but at that cheap its not worth arguing with dealer, who will probably say its the TB since its ported out or the cars tuned, etc...
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Just an update... The connector wasn't corroded or such... So installed the new pedal assy, and after 30 miles no issues.
I'll give an update after some more miles!
Hope I'm good for a while!
I'll give an update after some more miles!
Hope I'm good for a while!
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
No luck! Got about a hundred miles in and it popped back up last night...
Thinking now its probably the TB... Kinda sux cause the one I have is ported and will have to buy another and dont think the porters out there want another previously ported one as a core...
Also sure as hell hope its not some kind of crazy tuning anomaly...
I used a Tech 2 today to do a "Throttle Sweep" and I dont know if that actually re-learns the TPS volatages or just checks theres no issues... But of course I had to clear the codes to get home, so nothing came up wrong.
A friend mentioned doing a TAC re-learn but couldnt find that anywhere to reset the TPS' unless that was the "Throttle Sweep"
Give it one more round, but if that code comes back Ill have to spring for a TB I guess :-/
Any ideas????????
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Brett Foote
Moderator emeritus
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
Using the PDF Bill attached, you should be able to verify the function of the 2 TPS sensors. There is resistance and voltage checks listed in the PDF. Bottom line, I think you're down to the TB or the ECM. Check the function of the 2 sensors with a tech 2 or a VOM. If the sensors are working, then the PDF points at the ECM.
Elmer
Elmer
Racer
Joined: Apr 2012
Posts: 314
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From: Ontario
The Car's Environment
What kind of an environment are these problem cars used in? Are they winter driven or along the ocean where salt is a problem? Could be a wet year round climate. What kind of mileage when the problems show up? I understand that you need very good battery connections and good grounds. Poor grounding was a problem even in the old days once the cars got some years on them.
Moderator emeritus
Joined: Jun 2001
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Using the PDF Bill attached, you should be able to verify the function of the 2 TPS sensors. There is resistance and voltage checks listed in the PDF. Bottom line, I think you're down to the TB or the ECM. Check the function of the 2 sensors with a tech 2 or a VOM. If the sensors are working, then the PDF points at the ECM.
Elmer
Elmer
I looked over that PDF and a lot of it seems like Tech Jargon to me... Im gonna copy over a PM I sent back to Bill, maybe you could help me decipher some of those things....
What kind of an environment are these problem cars used in? Are they winter driven or along the ocean where salt is a problem? Could be a wet year round climate. What kind of mileage when the problems show up? I understand that you need very good battery connections and good grounds. Poor grounding was a problem even in the old days once the cars got some years on them.
Bill... First off thank you so much for sending me all this info!! Secondly, sorry I took soo long to get back to you! Just got a new boat last Tuesday and been a mad rush getting it all setup but its finally in the water so back to this car now!
When I had the Tech II, it had some test where it opened the TB from closed to WOT extremely slowly and showed the TPS 1 and TPS 2 voltages changing slowly.. and at the end it showed that it agree'd the whole time.
I really wasnt familiar with the Tech II but that was what I remember doing... I can get it back again if theres some other way or some other test I should be doing??
I would think this was the part titled "Circuit/System Verification" quoted below?? If not, how do I go about testing them with a DVM or the Tech II if I get it back?
Under the "Circuit/System Testing" part, I have a few questions... Im somewhat familiar with electrical stuff, like checking voltage and continuity, but confused by a lot of the technical talk in the PDF file. but want to be sure im doing it right. I think its just easiest to quote it and add my questions by the area...
I see a few different references to circuit, but not sure where to find these circuits... Im thinking its just tech jargon and maybe the TB connector, but not sure
- Step 2, low reference circuit terminal
- Step 3, 5-volt reference circuit terminal
- Steps 4 & 5, signal circuit terminal
- Step 10 - Im totally confused... Where and how am I checking the resistance, on the TB, the wiring connector closest to the TB, the connectors on the ECM, or??
- Step 11 - what does it mean to test for infinite resistance??
After looking this over multiple times, I feel like maybe its over my head?? but maybe if you could explain it a bit more to me Id get it...
Really appreciate your help as I really dont want to bring it to a dealer as I feel like theyre just gonna blame it on the modifications and tune and say to replace the ECM, and I may just end up with the problem again, out that money!
When I had the Tech II, it had some test where it opened the TB from closed to WOT extremely slowly and showed the TPS 1 and TPS 2 voltages changing slowly.. and at the end it showed that it agree'd the whole time.
I really wasnt familiar with the Tech II but that was what I remember doing... I can get it back again if theres some other way or some other test I should be doing??
I would think this was the part titled "Circuit/System Verification" quoted below?? If not, how do I go about testing them with a DVM or the Tech II if I get it back?
Circuit/System Verification
1. Ignition ON, observe the scan tool TP sensor 1 voltage parameter. The reading should be between 4.75-0.35 volts and change with accelerator pedal input.
2. Ignition ON, observe the scan tool TP sensor 2 voltage parameter. The reading should be between 0.25-4.59 volts and change with accelerator pedal input.
3. Ignition ON, observe the scan tool TP sensor 1 and 2 parameter. The scan tool should indicate agree.
4. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC, or within the conditions that you observed from the Freeze Frame/Failure Records.
5. Verify that DTC P0120 or P0220 are not the only throttle position DTCs set.
⇒
If DTC P0120 or P0220 are the only DTCs set, replace the control module.
6. Verify that DTCs P0641 or P0651 are not set.
⇒
If DTC P0641 or P0651 is set, refer to DTC P0641 or P0651.
7. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
1. Ignition ON, observe the scan tool TP sensor 1 voltage parameter. The reading should be between 4.75-0.35 volts and change with accelerator pedal input.
2. Ignition ON, observe the scan tool TP sensor 2 voltage parameter. The reading should be between 0.25-4.59 volts and change with accelerator pedal input.
3. Ignition ON, observe the scan tool TP sensor 1 and 2 parameter. The scan tool should indicate agree.
4. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC, or within the conditions that you observed from the Freeze Frame/Failure Records.
5. Verify that DTC P0120 or P0220 are not the only throttle position DTCs set.
⇒
If DTC P0120 or P0220 are the only DTCs set, replace the control module.
6. Verify that DTCs P0641 or P0651 are not set.
⇒
If DTC P0641 or P0651 is set, refer to DTC P0641 or P0651.
7. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Under the "Circuit/System Testing" part, I have a few questions... Im somewhat familiar with electrical stuff, like checking voltage and continuity, but confused by a lot of the technical talk in the PDF file. but want to be sure im doing it right. I think its just easiest to quote it and add my questions by the area...
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the throttle body. Allow up to 2 minutes for the ECM to completely power down.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.
⇒ (Which/where is the low reference circuit and this "terminal C" I am testing??
If greater than 5 ohms, test the low reference circuit for an open/high resistance. (How or what does it mean to test for open/high resistance??) If the circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between low reference circuit terminal E and ground.
⇒
If less than 4.8 volts, test 5-volt reference circuit for a short to ground (Where is this that I am testing, and To test for short to ground, simply check the continuity from there to a ground/negtive, correct? Pretty sure thats the setting if you place a lead on battery negative and another lead to frame/motor itll give you an audible sound on my DVM.)or an open/high resistance. If the circuit tests normal, replace the ECM.
⇒
If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. (How to test for short to voltage??) If the circuit tests normal, replace the ECM.
4. Verify the scan tool TP sensor 1 voltage is less than 0.1 volt.
⇒
If greater than 0.1 volt, test the signal circuit terminal D for a short to voltage. (Where is this signal circuit terminal??)If the circuit tests normal, replace the ECM.
5. Verify the scan tool TP sensor 2 voltage is greater than 4.8 volts.
⇒
If less than 4.8 volts, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the ECM.
6. Install a 3A fused jumper wire between the signal circuit terminal D and the 5-volt reference circuit terminal E of the TP sensor 1. Verify the TP sensor 1 voltage is greater than 4.8 volts.
⇒
If less than 4.8 volts, test the TP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
7. Install a test lamp between the signal circuit terminal F of the TP sensor 2 and ground. The test lamp should not illuminate.
⇒
If the test lamp illuminates, test the TP sensor 2 signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
8. Install a 3A fused jumper wire between the signal circuit terminal F and the low reference circuit terminal C of the TP sensor 2. Verify that the TP sensor 2 voltage is less than 0.1 volt.
⇒
If greater than 1.0 volt, test the TP sensor 2 signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
9. Ignition OFF, disconnect the harness connector at the ECM.
10. Test for less than 5 ohms on all TP sensor circuits between the following terminals:
•
ECM X2 signal circuit terminal 65 to TP terminal D
•
ECM X2 signal circuit terminal 63 to TP terminal F
•
ECM X2 5-volt reference circuit terminal 3 to terminal E
⇒
If greater than 5 ohms, repair the affected circuit for open/high resistance.
11. Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor signal circuit terminal F.
⇒
If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
12. If all circuits test normal, replace the throttle body.
1. Ignition OFF, disconnect the harness connector at the throttle body. Allow up to 2 minutes for the ECM to completely power down.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.
⇒ (Which/where is the low reference circuit and this "terminal C" I am testing??
If greater than 5 ohms, test the low reference circuit for an open/high resistance. (How or what does it mean to test for open/high resistance??) If the circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between low reference circuit terminal E and ground.
⇒
If less than 4.8 volts, test 5-volt reference circuit for a short to ground (Where is this that I am testing, and To test for short to ground, simply check the continuity from there to a ground/negtive, correct? Pretty sure thats the setting if you place a lead on battery negative and another lead to frame/motor itll give you an audible sound on my DVM.)or an open/high resistance. If the circuit tests normal, replace the ECM.
⇒
If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. (How to test for short to voltage??) If the circuit tests normal, replace the ECM.
4. Verify the scan tool TP sensor 1 voltage is less than 0.1 volt.
⇒
If greater than 0.1 volt, test the signal circuit terminal D for a short to voltage. (Where is this signal circuit terminal??)If the circuit tests normal, replace the ECM.
5. Verify the scan tool TP sensor 2 voltage is greater than 4.8 volts.
⇒
If less than 4.8 volts, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the ECM.
6. Install a 3A fused jumper wire between the signal circuit terminal D and the 5-volt reference circuit terminal E of the TP sensor 1. Verify the TP sensor 1 voltage is greater than 4.8 volts.
⇒
If less than 4.8 volts, test the TP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
7. Install a test lamp between the signal circuit terminal F of the TP sensor 2 and ground. The test lamp should not illuminate.
⇒
If the test lamp illuminates, test the TP sensor 2 signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
8. Install a 3A fused jumper wire between the signal circuit terminal F and the low reference circuit terminal C of the TP sensor 2. Verify that the TP sensor 2 voltage is less than 0.1 volt.
⇒
If greater than 1.0 volt, test the TP sensor 2 signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
9. Ignition OFF, disconnect the harness connector at the ECM.
10. Test for less than 5 ohms on all TP sensor circuits between the following terminals:
•
ECM X2 signal circuit terminal 65 to TP terminal D
•
ECM X2 signal circuit terminal 63 to TP terminal F
•
ECM X2 5-volt reference circuit terminal 3 to terminal E
⇒
If greater than 5 ohms, repair the affected circuit for open/high resistance.
11. Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor signal circuit terminal F.
⇒
If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
12. If all circuits test normal, replace the throttle body.
- Step 2, low reference circuit terminal
- Step 3, 5-volt reference circuit terminal
- Steps 4 & 5, signal circuit terminal
- Step 10 - Im totally confused... Where and how am I checking the resistance, on the TB, the wiring connector closest to the TB, the connectors on the ECM, or??
- Step 11 - what does it mean to test for infinite resistance??
After looking this over multiple times, I feel like maybe its over my head?? but maybe if you could explain it a bit more to me Id get it...
Really appreciate your help as I really dont want to bring it to a dealer as I feel like theyre just gonna blame it on the modifications and tune and say to replace the ECM, and I may just end up with the problem again, out that money!
Drifting
Joined: Jan 2005
Posts: 1,827
Likes: 301
From: Tucson Arizona
St. Jude Donor '08
Some answers
The male electrical connector on my 2005 C6 throttle body as you look at it from the passenger side has the following markings on it.
top left pin - D top right pin - A
middle left pin - E middle right pin - B
bottom left pin - F bottom right pin - C
these markings seem to correspond to the instructions in the three page PDF for testing purposes.
___________
| |D |A |
| |E |B |
| |F |C |
|__________|
top left pin - D top right pin - A
middle left pin - E middle right pin - B
bottom left pin - F bottom right pin - C
these markings seem to correspond to the instructions in the three page PDF for testing purposes.
___________
| |D |A |
| |E |B |
| |F |C |
|__________|
Drifting
Joined: Jan 2005
Posts: 1,827
Likes: 301
From: Tucson Arizona
St. Jude Donor '08
If you have replaced the TB then the problem is either a bad connection in the plug, the wiring or a bad ECM per the diagnostic procedures in the manual under these codes.
Team Owner
Joined: Sep 2000
Posts: 25,009
Likes: 2,707
From: Far NW 'burbs of Chicago
St. Jude Donor '13
Sorry for the late reply-
We had a similar problem on our 2006 A6- I'd be driving along normally and suddenly the engine would go to about 1/4 power, CEL light would come on, and DIC would display Reduced Engine Power. I don't recall a Service Traction System warning, but perhaps I've forgotten that.
Anyway, the first dealer (we were on vacation) replaced the gas pedal. That worked for about a month, then the problem came back. Next time back home, they replaced some wiring but I don't recall where. That fix only worked for a week, back in the shop. This time the tech had some long phone discussions with GM and ended up replacing some more wiring. It was ok for us after that, but we bought a new 2009 a few months later and I only know that the new owner of our 2006 was happy with the car several months afterward, so I think the problem didn't come back.
Our car was unmodified but was out of 3/36 warranty for all this, GMPP picked up every penny of the cost, which I don't have numbers for but must have been pretty expensive.
We had a similar problem on our 2006 A6- I'd be driving along normally and suddenly the engine would go to about 1/4 power, CEL light would come on, and DIC would display Reduced Engine Power. I don't recall a Service Traction System warning, but perhaps I've forgotten that.
Anyway, the first dealer (we were on vacation) replaced the gas pedal. That worked for about a month, then the problem came back. Next time back home, they replaced some wiring but I don't recall where. That fix only worked for a week, back in the shop. This time the tech had some long phone discussions with GM and ended up replacing some more wiring. It was ok for us after that, but we bought a new 2009 a few months later and I only know that the new owner of our 2006 was happy with the car several months afterward, so I think the problem didn't come back.
Our car was unmodified but was out of 3/36 warranty for all this, GMPP picked up every penny of the cost, which I don't have numbers for but must have been pretty expensive.
Last edited by Gearhead Jim; Nov 8, 2012 at 08:55 PM.