PCM code PO748
Thread Starter
Instructor
Joined: Jul 2005
Posts: 103
Likes: 1
PCM code PO748
Hey guys
Have a 97 AT vette I purchased used some months back.
Checked history codes today and the only one I could not find, on a list posted here, is:PCM "PO748"
Anyone know what this one is?
Thanks
Have a 97 AT vette I purchased used some months back.
Checked history codes today and the only one I could not find, on a list posted here, is:PCM "PO748"
Anyone know what this one is?
Thanks
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
P0748 is related to your automatic transmission .... from the Service Manual ....
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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.
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Bottom line ... I'd delete the DTC and see if it comes back. It's quite possible it was a "wiring glitch" that turned it on, as the wiring diagram for this shows only direct wiring between the PCM and the Pressure Control Solenoid in the automatic transmission.
If the problem continues, replacing the PC solenoid valve is the standard "fix" for this problem.
------------------------------------------------------------
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.
------------------------------------------------------------
Bottom line ... I'd delete the DTC and see if it comes back. It's quite possible it was a "wiring glitch" that turned it on, as the wiring diagram for this shows only direct wiring between the PCM and the Pressure Control Solenoid in the automatic transmission.
If the problem continues, replacing the PC solenoid valve is the standard "fix" for this problem.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 103
Likes: 1
Thanks much for the info Black Z06.
Damm, and I just had the trans fluid and filter changed.
Well, it was a history code. I'll see if it comes back.
I am always impressed on how much you guys know about these cars!
Where do you find the time? Although I assume some of you must do this for a living.
Thanks again
Bob
Damm, and I just had the trans fluid and filter changed.
Well, it was a history code. I'll see if it comes back.
I am always impressed on how much you guys know about these cars!
Where do you find the time? Although I assume some of you must do this for a living.
Thanks again
Bob
