Please Help With 97 Vette!!!!!!
Thread Starter
Instructor
Joined: Feb 2008
Posts: 118
Likes: 1
From: COLUMBUS OHIO
Please Help With 97 Vette!!!!!!
Do these cars have some kind of safe mode which puts it into a limp mode which we can reset? My car pulled a check engine the other day and it said drivers side 02. I cleared the code, but ever since my car doesnt want to accelerate hard anymore. Its very sluggish. The check engine light has not turned back on after resetting so Im a little confused. My car is an a4. Thanks for any and all help.
Safety Car
Joined: Dec 2004
Posts: 3,526
Likes: 20
From: Santa Fe TX
If the front o2's are off it can cause real problems with fuel mixture.
Rear o2 codes normally are not a problem, but if the rear o2's are throwing a code because of a catalyst failure, that can also cause severe problems, like a "banana in the tailpipe."
Even if you reset the light, you should use the DIC to read the codes (hold options, press fuel 4 times, read codes).
Some codes require 2 ignition cycles to throw a light, so the code could be active without a CE light.
Rear o2 codes normally are not a problem, but if the rear o2's are throwing a code because of a catalyst failure, that can also cause severe problems, like a "banana in the tailpipe."
Even if you reset the light, you should use the DIC to read the codes (hold options, press fuel 4 times, read codes).
Some codes require 2 ignition cycles to throw a light, so the code could be active without a CE light.
Banned Scam/Spammer
Joined: Jul 2006
Posts: 2,911
Likes: 10
From: Simi Valley CA
Yes, they have a limp mode.. but you'd only be able to get to the curb.
Yes, sounds like your o2 went out. Replace it.. 10 min job. Thats why it won't accelerate.. it's running too rich. You could cause cylinder washout as well as destroying your cats.
Yes, sounds like your o2 went out. Replace it.. 10 min job. Thats why it won't accelerate.. it's running too rich. You could cause cylinder washout as well as destroying your cats.
Last edited by Todd157k; Jul 24, 2008 at 12:00 PM.
Thread Starter
Instructor
Joined: Feb 2008
Posts: 118
Likes: 1
From: COLUMBUS OHIO
If the front o2's are off it can cause real problems with fuel mixture.
Rear o2 codes normally are not a problem, but if the rear o2's are throwing a code because of a catalyst failure, that can also cause severe problems, like a "banana in the tailpipe."
Even if you reset the light, you should use the DIC to read the codes (hold options, press fuel 4 times, read codes).
Some codes require 2 ignition cycles to throw a light, so the code could be active without a CE light.
Rear o2 codes normally are not a problem, but if the rear o2's are throwing a code because of a catalyst failure, that can also cause severe problems, like a "banana in the tailpipe."
Even if you reset the light, you should use the DIC to read the codes (hold options, press fuel 4 times, read codes).
Some codes require 2 ignition cycles to throw a light, so the code could be active without a CE light.
Drifting
Joined: May 2005
Posts: 1,590
Likes: 1
From: Littleton Colorado
Thanks for the info guys. The problem was with the front drivers 02 when I read the code. Sorry but what does DIC mean and how can I get one or who would have one? So a bad o2 would make my car feel this sluggish? Im talking my car doesnt even kick down and take off anymore from a dead stop or even a roll. Its like it wants to but it just doesnt have any ***** anymore and my CE light hasnt been back on since Ive reset it and thats been a few weeks now. Thanks again guys for all your help.
Yes, a bad O2 will cause it to run very badly. But, I would pull all the codes just to be sure. The front O2s are the primary way for the computer to know how engine is doing, based on the O2 information the computer will add or remove fuel. With faulty info it will not be able to set the fuel correctly. Also, your O2 sensor may be faulty, but not enough to trip the code again. It still can make it run badly.
Does if run better at cold startup? If not, you may have another issue. so pull all your codes and review them. Search on the forum for info and post them if you don't know what to do.
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
Thanks for the info guys. The problem was with the front drivers 02 when I read the code. Sorry but what does DIC mean and how can I get one or who would have one? So a bad o2 would make my car feel this sluggish? Im talking my car doesnt even kick down and take off anymore from a dead stop or even a roll. Its like it wants to but it just doesnt have any ***** anymore and my CE light hasnt been back on since Ive reset it and thats been a few weeks now. Thanks again guys for all your help.
Uhhhh ... we all have a DIC, even the girls here who own Corvettes .... It stands for Digital Information Center .... it is that display that says "Corvette by Chevrolet" when you start the car.
How did you read the code and delete it ???? Let me guess, some kinda scanner. Well throw the scanner away .... most can only display engine codes ..... the C5 Corvette has its own built in "code reader" that reads every code in every computer in the car.
Go here ....
https://www.corvetteforum.com/techti...D=26&TopicID=1
When the AUTOMATIC display completes it will enter MANUAL mode. In that mode display and write down what codes you have.
A code looks like this ...... P 1234 C
The first letter will be either a P, B, C, or U ..... indicating which system the code is for.
The following 4 numbers are the code
The last letter will be a C or an H (sometimes both).
Post the ENTIRE code (as in the example ..... P1234C), and list ALL the codes found.
======================
Chevy put the CHECK ENGINE light on your dashboard for a reason ..... mainly they think it might be a good idea to FIX a problem because SOMETHING is wrong with the engine. "Deleting" a code doesn't fix anything. Whatever causes a code should be investigated and repaired. Deleting the code is like resetting your "oil life" to get rid of those annoying CHANGE OIL messages .... it doesn't put clean oil in the engine, it just gets rid of the reminders.
Thread Starter
Instructor
Joined: Feb 2008
Posts: 118
Likes: 1
From: COLUMBUS OHIO
[SubTopicID=26&TopicID=1[/url]
======================
[/QUOTE]
Chevy put the CHECK ENGINE light on your dashboard for a reason ..... mainly they think it might be a good idea to FIX a problem because SOMETHING is wrong with the engine. "Deleting" a code doesn't fix anything. Whatever causes a code should be investigated and repaired. Deleting the code is like resetting your "oil life" to get rid of those annoying CHANGE OIL messages .... it doesn't put clean oil in the engine, it just gets rid of the reminders.
But if there is still a problem with lets say my o2 shouldnt the check engine light come back on? I did right down the codes but there is one that I cant find. Does anyone know what code P0748 is. Thanks again to all for the help.
======================
[/QUOTE]Chevy put the CHECK ENGINE light on your dashboard for a reason ..... mainly they think it might be a good idea to FIX a problem because SOMETHING is wrong with the engine. "Deleting" a code doesn't fix anything. Whatever causes a code should be investigated and repaired. Deleting the code is like resetting your "oil life" to get rid of those annoying CHANGE OIL messages .... it doesn't put clean oil in the engine, it just gets rid of the reminders.
But if there is still a problem with lets say my o2 shouldnt the check engine light come back on? I did right down the codes but there is one that I cant find. Does anyone know what code P0748 is. Thanks again to all for the help.
Last edited by C5CORVETTE1; Jul 24, 2008 at 04:34 PM.
Tech Contributor
Joined: Oct 1999
Posts: 41,058
Likes: 9,822
From: Charlotte, NC (formerly Endicott, NY)
It looks like you have an Automatic Transmission problem. Here is the GM Service Manual diagnostic procedure for code P0748.
DTC P0748 Pressure Control Solenoid Circuit Electrical
Circuit Description
The Pressure Control Solenoid Valve (PC Sol. Valve) is an electronic device that regulates transmission line pressure based on the current flow through it's coil windings. The magnetic field produced by the coil moves the solenoid's internal valve which varies the fluid pressure to the pressure regulator valve. The Powertrain Control Module (PCM) controls the PC Sol. Valve by applying a varying amount of amperage to the Solenoid. The applied amperage varies 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 Sol. Valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time (non-energized) or no current flow. Approximately 60% 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 Position (TP) voltage, the engine speed and other inputs.
When the PCM detects a continuous open or short to ground in the PC Sol. Valve circuit or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.
Conditions for Setting the DTC
• The system voltage is 10-18 volts.
• The engine is running.
• The difference between the PC Sol. Valve actual return amperage and the desired amperage is 0.16 amp or greater.
Action Taken When the DTC Sets
• The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
• The PC Sol. Valve is OFF.
• The PCM freezes shift adapts from being updated.
• DTC P0748 stores in PCM history.
Conditions for Clearing the DTC
• A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
• The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.
Diagnostic Aids
• Inspect the wiring at the PCM, the transmission 20-way connector and all other circuit connecting points for the following conditions:
o A bent terminal
o A backed out terminal
o A damaged terminal
o Poor terminal tension
o A chafed wire
o A broken wire inside the insulation
o Moisture intrusion
o Corrosion
• When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step 2. This step tests the ability of the PCM to command the PC Sol. Valve.
Step 3. This step tests the PC Sol. Valve and Automatic Transmission Wiring Harness Assembly for incorrect resistance.
DTC P0748 Pressure Control Solenoid Valve (PC Sol. Valve) Circuit -- Electrical
Step
Action Value(s) Yes No
Step 1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? -- Go to Step 2
Go to Powertrain OBD System Check
Step 2
1. Install the Scan Tool .
2. With the engine OFF, turn the ignition switch to the RUN position.
Important
Before clearing the DTC(s), use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM.
3. Record the DTC Failure Records, then clear the DTC(s).
4. Start the engine.
5. Using the transmission output control function on the scan tool, apply 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 Diagnostic Aids Go to Step 3
Step 3
1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector.
3. Install the J 39775 Jumper Harness on the transmission side of the 20-way connector.
4. Using the J 39200 Digital Multimeter (DMM) and the J 35616-A Connector Test Adapter Kit, measure the resistance between terminal C and terminal D.
Is the resistance within the specified range? 3-7 ohms Go to Step 8
Go to Step 4
Step 4
Is the resistance greater than the specified value? 7 ohms Go to Step 5
Go to Step 6
Step 5
1. Inspect the Automatic Transmission Wiring Harness Assembly for an open. Refer to General Electrical Diagnosis Procedures.
2. Replace the harness if necessary.
Did you find an open condition? -- Go to Step 19
Go to Step 10
Step 6
Is the resistance less than the specified value? 3 ohms Go to Step 7
--
Step 7
1. Inspect the Automatic Transmission Wiring Harness Assembly for a shorted together condition. Refer to General Electrical Diagnosis Procedures.
2. Replace the harness if necessary.
Did you find a shorted condition? -- Go to Step 19
Go to Step 10
Step 8
Measure the resistance from terminal C to the transmission case.
Is the resistance less than the specified value? 9 ohms Go to Step 9
Go to Step 11
Step 9
1. Inspect the Automatic Transmission Wiring Harness Assembly for a short to ground. Refer to General Electrical Diagnosis Procedures.
2. Replace the harness if necessary.
Did you find a short to ground condition? -- Go to Step 19
Go to Step 10
Step 10
Replace the PC Sol. Valve.
Refer to Control and Shift Solenoids Replacement.
Is the replacement complete? -- Go to Step 19
--
Step 11
1. Disconnect the J 39775 Jumper Harness from the transmission side of the 20-way connector.
2. Reconnect the transmission 20-way connector.
3. Disconnect the C2 (blue) PCM connector.
4. Using the J 39200 DMM and the J 35616-A Connector Test Adapter Kit, measure the resistance between terminal C2-39 and C2-36.
Is the resistance within the specified range? 3-7 ohms Go to Step 16
Go to Step 12
Step 12
Is the resistance greater than the specified value? 7 ohms Go to Step 13
Go to Step 14
Step 13
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) for an open.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis Procedures.
Did you find and correct an open condition? -- Go to Step 19
--
Step 14
Is the resistance less than the specified value? 3 ohms Go to Step 15
--
Step 15
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) for a shorted together condition.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis Procedures.
Did you find and correct a shorted condition? -- Go to Step 19
--
Step 16
Using the J 39200 DMM and the J 35616-A Connector Test Adapter Kit, measure the resistance from terminal C2-39 to ground.
Is the resistance less than the specified value? 9 ohms Go to Step 17
Go to Step 18
Step 17
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) for a short to ground.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis Procedures.
Did you find and correct the short to ground condition? -- Go to Step 19
--
Step 18
Replace the PCM.
Refer to PCM/TAC Module Replacement.
Is the replacement complete? -- Go to Step 19
--
Step 19
In order to verify your repair, perform the following procedure:
1. Select DTC.
2. Select Clear Info.
3. Start the engine and ensure that the difference between the PC Sol. Valve actual return amperage and the desired amperage is less than 0.16 amp.
4. Select Specific DTC. Enter DTC P0748.
Has the test run and passed? -- System OK Begin the diagnosis again. Go to Step 1
Bill
DTC P0748 Pressure Control Solenoid Circuit Electrical
Circuit Description
The Pressure Control Solenoid Valve (PC Sol. Valve) is an electronic device that regulates transmission line pressure based on the current flow through it's coil windings. The magnetic field produced by the coil moves the solenoid's internal valve which varies the fluid pressure to the pressure regulator valve. The Powertrain Control Module (PCM) controls the PC Sol. Valve by applying a varying amount of amperage to the Solenoid. The applied amperage varies 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 Sol. Valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time (non-energized) or no current flow. Approximately 60% 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 Position (TP) voltage, the engine speed and other inputs.
When the PCM detects a continuous open or short to ground in the PC Sol. Valve circuit or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.
Conditions for Setting the DTC
• The system voltage is 10-18 volts.
• The engine is running.
• The difference between the PC Sol. Valve actual return amperage and the desired amperage is 0.16 amp or greater.
Action Taken When the DTC Sets
• The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
• The PC Sol. Valve is OFF.
• The PCM freezes shift adapts from being updated.
• DTC P0748 stores in PCM history.
Conditions for Clearing the DTC
• A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
• The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.
Diagnostic Aids
• Inspect the wiring at the PCM, the transmission 20-way connector and all other circuit connecting points for the following conditions:
o A bent terminal
o A backed out terminal
o A damaged terminal
o Poor terminal tension
o A chafed wire
o A broken wire inside the insulation
o Moisture intrusion
o Corrosion
• When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step 2. This step tests the ability of the PCM to command the PC Sol. Valve.
Step 3. This step tests the PC Sol. Valve and Automatic Transmission Wiring Harness Assembly for incorrect resistance.
DTC P0748 Pressure Control Solenoid Valve (PC Sol. Valve) Circuit -- Electrical
Step
Action Value(s) Yes No
Step 1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? -- Go to Step 2
Go to Powertrain OBD System Check
Step 2
1. Install the Scan Tool .
2. With the engine OFF, turn the ignition switch to the RUN position.
Important
Before clearing the DTC(s), use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM.
3. Record the DTC Failure Records, then clear the DTC(s).
4. Start the engine.
5. Using the transmission output control function on the scan tool, apply 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 Diagnostic Aids Go to Step 3
Step 3
1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector.
3. Install the J 39775 Jumper Harness on the transmission side of the 20-way connector.
4. Using the J 39200 Digital Multimeter (DMM) and the J 35616-A Connector Test Adapter Kit, measure the resistance between terminal C and terminal D.
Is the resistance within the specified range? 3-7 ohms Go to Step 8
Go to Step 4
Step 4
Is the resistance greater than the specified value? 7 ohms Go to Step 5
Go to Step 6
Step 5
1. Inspect the Automatic Transmission Wiring Harness Assembly for an open. Refer to General Electrical Diagnosis Procedures.
2. Replace the harness if necessary.
Did you find an open condition? -- Go to Step 19
Go to Step 10
Step 6
Is the resistance less than the specified value? 3 ohms Go to Step 7
--
Step 7
1. Inspect the Automatic Transmission Wiring Harness Assembly for a shorted together condition. Refer to General Electrical Diagnosis Procedures.
2. Replace the harness if necessary.
Did you find a shorted condition? -- Go to Step 19
Go to Step 10
Step 8
Measure the resistance from terminal C to the transmission case.
Is the resistance less than the specified value? 9 ohms Go to Step 9
Go to Step 11
Step 9
1. Inspect the Automatic Transmission Wiring Harness Assembly for a short to ground. Refer to General Electrical Diagnosis Procedures.
2. Replace the harness if necessary.
Did you find a short to ground condition? -- Go to Step 19
Go to Step 10
Step 10
Replace the PC Sol. Valve.
Refer to Control and Shift Solenoids Replacement.
Is the replacement complete? -- Go to Step 19
--
Step 11
1. Disconnect the J 39775 Jumper Harness from the transmission side of the 20-way connector.
2. Reconnect the transmission 20-way connector.
3. Disconnect the C2 (blue) PCM connector.
4. Using the J 39200 DMM and the J 35616-A Connector Test Adapter Kit, measure the resistance between terminal C2-39 and C2-36.
Is the resistance within the specified range? 3-7 ohms Go to Step 16
Go to Step 12
Step 12
Is the resistance greater than the specified value? 7 ohms Go to Step 13
Go to Step 14
Step 13
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) for an open.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis Procedures.
Did you find and correct an open condition? -- Go to Step 19
--
Step 14
Is the resistance less than the specified value? 3 ohms Go to Step 15
--
Step 15
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) for a shorted together condition.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis Procedures.
Did you find and correct a shorted condition? -- Go to Step 19
--
Step 16
Using the J 39200 DMM and the J 35616-A Connector Test Adapter Kit, measure the resistance from terminal C2-39 to ground.
Is the resistance less than the specified value? 9 ohms Go to Step 17
Go to Step 18
Step 17
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) for a short to ground.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis Procedures.
Did you find and correct the short to ground condition? -- Go to Step 19
--
Step 18
Replace the PCM.
Refer to PCM/TAC Module Replacement.
Is the replacement complete? -- Go to Step 19
--
Step 19
In order to verify your repair, perform the following procedure:
1. Select DTC.
2. Select Clear Info.
3. Start the engine and ensure that the difference between the PC Sol. Valve actual return amperage and the desired amperage is less than 0.16 amp.
4. Select Specific DTC. Enter DTC P0748.
Has the test run and passed? -- System OK Begin the diagnosis again. Go to Step 1
Bill
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