Lost power
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6th Gear
Joined: May 2011
Posts: 6
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Lost power
I have a 2004 vet and installed longtube headers and off road pipe no cats when done test drove and car had no power any help would be nice did have to replace plug wires to do to broke when removed
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
Your going to have to dig a little deeper in the definition file.~~~~~~ No ELECTRICAL POWER, NO HP, ????????????????
Remember to post your DTC..
READING YOUR Engine Diagnostic Trouble Codes (DTC)
This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.
The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.
Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.
If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.
NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.
These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs
Here are some very good sites that explain what DTC mean:
http://www.gearchatter.com/viewtopic11755.php
http://www.obd-codes.com/trouble_cod...d-ii-codes.php
Make sure to include the H or C suffix when you post your DTCs!!~~~
Remember to post your DTC..
READING YOUR Engine Diagnostic Trouble Codes (DTC)
This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.
The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.
Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.
If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.
NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.
These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs
Here are some very good sites that explain what DTC mean:
http://www.gearchatter.com/viewtopic11755.php
http://www.obd-codes.com/trouble_cod...d-ii-codes.php
Make sure to include the H or C suffix when you post your DTCs!!~~~
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
When accelerating do you or did you ever see the CHECK ENGINE LIGHT flash??? If you didn't look for that, take a drive and see if that happens. If you see the CEL FLASH, "IMMEDIATELY" without turning the engine off, check for DTC using the DIC. If you have any misfires, you will see a P-0300 DTC.
If none of that checks out, you better break out some EFI Live or HP Tuners and DATA LOG the PCM.
BC
BC
If none of that checks out, you better break out some EFI Live or HP Tuners and DATA LOG the PCM.
BC
BC
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
Uh,,,,,,,,,,,,,,,,,,,,,,,
Thats NOT good for power!!
DTC P0748
Circuit Description
The pressure control (PC) solenoid valve is an electronic device that regulates transmission line pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve. The powertrain control module (PCM) controls the PC solenoid valve by applying a varying amount of amperage to the solenoid. The applied amperage can vary from 0.1 to 1.1 amps. Low amperage, 0.1 amp, indicates high line pressure. High amperage, 1.1 amps, indicates low line pressure. The duty cycle of the PC solenoid valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time, non-energized, or no current flow. Approximately 60 percent at idle indicates maximum ON time, energized, or high current flow. The PCM determines the appropriate line pressure for a given load by comparing the throttle, engine speed and other inputs.
When the PCM detects a continuous open or short in the PC solenoid valve circuit, then DTC P0748 sets. DTC P0748 is a type C DTC.
Conditions for Running the DTC
The system voltage is 10-18 volts.
The engine is running.
Conditions for Setting the DTC
The PC solenoid valve duty cycle reaches its high limit, approximately 95 percent, or low limit, approximately 0 percent.
Action Taken When the DTC Sets
The PCM does not illuminate the malfunction indicator lamp (MIL).
The PC solenoid valve is OFF.
The PCM freezes transmission adapt functions.
The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
The PCM stores DTC P0748 in PCM history.
Conditions for Clearing the DTC
A scan tool can clear the DTC.
The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.
Diagnostic Aids
DTC P0748 may set under low voltage conditions caused by high electrical system demands.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
This step tests the ability of the PCM to command the PC solenoid valve.
This step tests the PC solenoid valve and automatic transmission (AT) wiring harness assembly for incorrect resistance.
DTC P0748 Step
Action
Value(s)
Yes
No
1
Did you perform the Diagnostic System Check - Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls in Engine Controls
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Important
Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
Record the DTC Failure Records.
Clear the DTC.
Start the engine.
Use the scan tool in order to command 0.1 amp through 1.0 amp while observing PC Sol. Ref. Current and PC Sol. Actual Current.
Is the PC Sol. Actual Current always within the specified value of the PC Sol. Ref. Current?
0.16 amp
Go to Intermittent Conditions in Engine Controls
Go to Step 3
3
Turn OFF the ignition.
Disconnect the AT inline 20-way connector.
Install the J 44152 Jumper Harness (20 pins) on the transmission side of the AT inline 20-way connector.
Using the DMM and the J 35616-B GM Terminal Test Kit, measure the resistance between terminals C and D of the J 44152 . Refer to Automatic Transmission Inline 20-Way Connector End View .
Does the resistance measure within the specified range?
3-7 ohms
Go to Step 5
Go to Step 4
4
Does the resistance measure greater than the specified value?
7 ohms
Go to Step 9
Go to Step 10
5
Measure the resistance from terminal C of the J 44152 to the transmission case.
Refer to Automatic Transmission Inline 20-Way Connector End View .
Does the resistance measure greater than the specified value?
250 K ohms
Go to Step 6
Go to Step 11
6
Disconnect the J 44152 from the transmission side of the AT inline 20-way connector.
Reconnect the transmission AT inline 20-way connector.
Disconnect the PCM connector C2.
Measure the resistance between PCM connector terminal C2-6 and terminal C2-8.
Does the resistance measure within the specified range?
3-7 ohms
Go to Step 8
Go to Step 7
7
Does the resistance measure greater than the specified value?
7 ohms
Go to Step 12
Go to Step 13
8
Using the DMM and the J 35616-B , measure the resistance from PCM connector terminal C2-6 to ground.
Does the resistance measure greater than the specified value?
250 K ohms
Go to Step 17
Go to Step 14
9
Test the high control circuit and the low control circuit of the PC solenoid for an open between the AT inline 20-way connector and the PC solenoid.
Refer to Testing for Continuity in Wiring Systems.
Did you find an open condition?
--
Go to Step 16
Go to Step 15
10
Test the high control circuit and the low control circuit of the PC solenoid for a shorted together condition between the AT inline 20-way connector and the PC solenoid.
Refer to Circuit Testing in Wiring Systems.
Did you find a shorted together condition?
--
Go to Step 16
Go to Step 15
11
Test the high control circuit and the low control circuit of the PC solenoid for a short to ground between the AT inline 20-way connector and the PC solenoid.
Refer to Testing for Short to Ground in Wiring Systems.
Did you find a short to ground condition?
--
Go to Step 16
Go to Step 15
12
Test the high control circuit and the low control circuit of the PC solenoid for an open between the PCM connector C2 and the AT inline 20-way connector.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 18
--
13
Test the high control circuit and the low control circuit of the PC solenoid for a shorted together condition between the PCM connector C2 and the AT inline 20-way connector.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 18
--
14
Test the high control circuit and the low control circuit of the PC solenoid for a short to ground between the PCM connector C2 and the AT inline 20-way connector.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 18
--
15
Replace the PC solenoid valve.
Refer to Valve Body and Pressure Switch Replacement .
Did you complete the replacement?
--
Go to Step 18
--
16
Replace the AT wiring harness assembly.
Refer to Valve Body and Pressure Switch Replacement .
Did you complete the replacement?
--
Go to Step 18
--
17
Test the high control circuit and the low control circuit of the PC solenoid for a short to voltage.
Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 19
Go to Step 18
18
Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
Did you complete the replacement?
--
Go to Step 19
--
19
Perform the following procedure in order to verify the repair:
Select DTC.
Select Clear Info.
Start the engine and ensure the following condition is met: The difference between the scan tool PC Sol. Actual Current and the PC Sol. Ref. Current is less than 0.16 amp.
Select Specific DTC.
Enter DTC P0748.
Has the test run and passed?
--
Go to Step 20
Go to Step 2
20
With the scan tool, observe the stored information, capture info, and DTC Info.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List in Engine Controls
System OK
--------------------------------------------------------------------------------
Document ID# 1215898
2004 Chevrolet Corvette
Thats NOT good for power!!DTC P0748
Circuit Description
The pressure control (PC) solenoid valve is an electronic device that regulates transmission line pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve. The powertrain control module (PCM) controls the PC solenoid valve by applying a varying amount of amperage to the solenoid. The applied amperage can vary from 0.1 to 1.1 amps. Low amperage, 0.1 amp, indicates high line pressure. High amperage, 1.1 amps, indicates low line pressure. The duty cycle of the PC solenoid valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time, non-energized, or no current flow. Approximately 60 percent at idle indicates maximum ON time, energized, or high current flow. The PCM determines the appropriate line pressure for a given load by comparing the throttle, engine speed and other inputs.
When the PCM detects a continuous open or short in the PC solenoid valve circuit, then DTC P0748 sets. DTC P0748 is a type C DTC.
Conditions for Running the DTC
The system voltage is 10-18 volts.
The engine is running.
Conditions for Setting the DTC
The PC solenoid valve duty cycle reaches its high limit, approximately 95 percent, or low limit, approximately 0 percent.
Action Taken When the DTC Sets
The PCM does not illuminate the malfunction indicator lamp (MIL).
The PC solenoid valve is OFF.
The PCM freezes transmission adapt functions.
The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
The PCM stores DTC P0748 in PCM history.
Conditions for Clearing the DTC
A scan tool can clear the DTC.
The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.
Diagnostic Aids
DTC P0748 may set under low voltage conditions caused by high electrical system demands.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
This step tests the ability of the PCM to command the PC solenoid valve.
This step tests the PC solenoid valve and automatic transmission (AT) wiring harness assembly for incorrect resistance.
DTC P0748 Step
Action
Value(s)
Yes
No
1
Did you perform the Diagnostic System Check - Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls in Engine Controls
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Important
Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
Record the DTC Failure Records.
Clear the DTC.
Start the engine.
Use the scan tool in order to command 0.1 amp through 1.0 amp while observing PC Sol. Ref. Current and PC Sol. Actual Current.
Is the PC Sol. Actual Current always within the specified value of the PC Sol. Ref. Current?
0.16 amp
Go to Intermittent Conditions in Engine Controls
Go to Step 3
3
Turn OFF the ignition.
Disconnect the AT inline 20-way connector.
Install the J 44152 Jumper Harness (20 pins) on the transmission side of the AT inline 20-way connector.
Using the DMM and the J 35616-B GM Terminal Test Kit, measure the resistance between terminals C and D of the J 44152 . Refer to Automatic Transmission Inline 20-Way Connector End View .
Does the resistance measure within the specified range?
3-7 ohms
Go to Step 5
Go to Step 4
4
Does the resistance measure greater than the specified value?
7 ohms
Go to Step 9
Go to Step 10
5
Measure the resistance from terminal C of the J 44152 to the transmission case.
Refer to Automatic Transmission Inline 20-Way Connector End View .
Does the resistance measure greater than the specified value?
250 K ohms
Go to Step 6
Go to Step 11
6
Disconnect the J 44152 from the transmission side of the AT inline 20-way connector.
Reconnect the transmission AT inline 20-way connector.
Disconnect the PCM connector C2.
Measure the resistance between PCM connector terminal C2-6 and terminal C2-8.
Does the resistance measure within the specified range?
3-7 ohms
Go to Step 8
Go to Step 7
7
Does the resistance measure greater than the specified value?
7 ohms
Go to Step 12
Go to Step 13
8
Using the DMM and the J 35616-B , measure the resistance from PCM connector terminal C2-6 to ground.
Does the resistance measure greater than the specified value?
250 K ohms
Go to Step 17
Go to Step 14
9
Test the high control circuit and the low control circuit of the PC solenoid for an open between the AT inline 20-way connector and the PC solenoid.
Refer to Testing for Continuity in Wiring Systems.
Did you find an open condition?
--
Go to Step 16
Go to Step 15
10
Test the high control circuit and the low control circuit of the PC solenoid for a shorted together condition between the AT inline 20-way connector and the PC solenoid.
Refer to Circuit Testing in Wiring Systems.
Did you find a shorted together condition?
--
Go to Step 16
Go to Step 15
11
Test the high control circuit and the low control circuit of the PC solenoid for a short to ground between the AT inline 20-way connector and the PC solenoid.
Refer to Testing for Short to Ground in Wiring Systems.
Did you find a short to ground condition?
--
Go to Step 16
Go to Step 15
12
Test the high control circuit and the low control circuit of the PC solenoid for an open between the PCM connector C2 and the AT inline 20-way connector.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 18
--
13
Test the high control circuit and the low control circuit of the PC solenoid for a shorted together condition between the PCM connector C2 and the AT inline 20-way connector.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 18
--
14
Test the high control circuit and the low control circuit of the PC solenoid for a short to ground between the PCM connector C2 and the AT inline 20-way connector.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 18
--
15
Replace the PC solenoid valve.
Refer to Valve Body and Pressure Switch Replacement .
Did you complete the replacement?
--
Go to Step 18
--
16
Replace the AT wiring harness assembly.
Refer to Valve Body and Pressure Switch Replacement .
Did you complete the replacement?
--
Go to Step 18
--
17
Test the high control circuit and the low control circuit of the PC solenoid for a short to voltage.
Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 19
Go to Step 18
18
Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
Did you complete the replacement?
--
Go to Step 19
--
19
Perform the following procedure in order to verify the repair:
Select DTC.
Select Clear Info.
Start the engine and ensure the following condition is met: The difference between the scan tool PC Sol. Actual Current and the PC Sol. Ref. Current is less than 0.16 amp.
Select Specific DTC.
Enter DTC P0748.
Has the test run and passed?
--
Go to Step 20
Go to Step 2
20
With the scan tool, observe the stored information, capture info, and DTC Info.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List in Engine Controls
System OK
--------------------------------------------------------------------------------
Document ID# 1215898
2004 Chevrolet Corvette
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