DTC P0748 Pressure Control Solenoid Circuit Electrical. GMC Truck Jimmy

Is the resistance less than the specified value?

3 ohms

Go to Step 7

Inspect the Automatic Transmission Wiring Harness Assembly for a shorted together condition. Refer to Electrical Diagnosis, Section 8A.
Replace the harness if necessary.

Did you find a problem?

Using the J 39200 DVOM and J 35616 Connector Test Adapter Kit, measure the resistance from terminal C to the transmission case.

Is the resistance less than the specified value?

250K ohms

Go to Step 9

Go to Step 11

Inspect the Automatic Transmission Wiring Harness Assembly for a short to ground. Refer to Electrical Diagnosis, Section 8A.
Replace the harness if necessary.

Did you find a problem?

Replace the PC Sol. Valve.

Refer to Pressure Control Solenoid Valve Replacement/4L60-E Automatic Transmission On-Vehicle Service.

Is the replacement complete?

Disconnect the J 39775 Jumper Harness from the transmission side of the 20-way connector.
Reconnect the transmission 20-way connector.
Disconnect the C2 (black) PCM connector.
Using the J 39200 DVOM and the J 35616 Connector Test Adapter Kit, measure the resistance from terminal C2-6 to ground.

Is the resistance greater than the specified value?

250K ohms

Go to Step 12

Inspect circuit 1228 and circuit 1229 for an open.

Repair the circuits if necessary.

Refer to Electrical Diagnosis, Section 8A.

Did you find a problem?

Go to Step 14

Inspect circuit 1228 and circuit 1229 for a short to ground.

Repair the circuits if necessary.

Refer to Electrical Diagnosis, Section 8A.

Did you find a problem?

Go to Step 14

Replace the PCM.

Refer to PCM Replacement, Section 6.

Is the replacement complete?

Begin the diagnosis again. Go to Step 1

In order to verify your repair, perform the following procedure:

Select DTC.
Select Clear Info.
Operate the vehicle under the following conditions:

•	The engine is running.

•	The difference between the PC Sol. Valve actual return amperage and the desired amperage is less than 0.16 amp.

Select Specific DTC. Enter DTC P0748.

Has the test run and passed?

System OK

DTC P0748 Pressure Control Solenoid Circuit Electrical 4.3L

Circuit Description

The Pressure Control Solenoid Valve (PC Sol. Valve) is a VCM-controlled device used to regulate the transmission line pressure. The VCM compares the TP voltage, the engine RPM and other inputs to determine the line pressure appropriate for a given load. The VCM applies a varying amperage to the PC Sol. Valve in order to regulate the pressure. The applied amperage can vary from 0.1 to 1.1 amps. The VCM monitors the amperage.

When the VCM 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 10-19 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 VCM freezes shift adapts from being updated.

•	The PC Sol. Valve is OFF.

•	The VCM does not illuminate the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the DTC

•	A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.

•	The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids

•	Inspect the wiring for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:

-	A bent terminal

-	A backed out terminal

-	A damaged terminal

-	Poor terminal tension

-	A chafed wire

-	A broken wire inside the insulation

•	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.

This step tests the ability of the VCM to command the PC Sol. Valve.

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 (4.3L)

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to OBD System Check

Install the scan tool.
With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. The Clear Info function will erase the data.

Record the DTC Failure Records.
While the engine is operating, put the transmission in Park.
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

Turn the ignition OFF.
Disconnect the transmission 20-way connector.
Install the J 39775 Jumper Harness on the transmission side of the 20-way connector.
Using the J 39200 DVOM and J 35616 Connector Test Adapter Kit, measure the resistance between terminals C and D.

Is the resistance within the specified range?

3-7 ohms

Go to Step 6

Go to Step 4

Disconnect the Automatic Transmission Wiring Harness Assembly at the PC Sol. Valve.
Measure the resistance of the PC Sol. Valve.

Is the resistance within the specified range?

3-7 ohms

Go to Step 5

Go to Step 8

Replace the Automatic Transmission Wiring Harness Assembly. Refer to 4L60-E Automatic Transmission On-Vehicle Service.

Is the replacement complete?

Measure the resistance from terminal C to the transmission case.

Is the resistance less than the specified value?

9 ohms

Go to Step 7

Go to Step 9

Inspect the Automatic Transmission Wiring Harness Assembly for a short to ground. Refer to Electrical Diagnosis, Section 8A. Replace the harness if necessary.

Did you find a problem?

Go to Step 8

Replace the PC Sol. Valve.

Refer to Pressure Control Solenoid Valve Replacement/4L60-E Automatic Transmission On-Vehicle Service.

Is the replacement complete?

Disconnect the J 39775 Jumper Harness from the transmission side of the 20-way connector.
Reconnect the transmission 20-way connector.
Disconnect the C3 (grey/clear) VCM connector.
Measure the resistance from terminal C3-6 to ground.

Is the resistance greater than the specified value?

9 ohms

Go to Step 11

Inspect circuit 1228 and circuit 1229 for an open. Repair the circuits if necessary.

Refer to Electrical Diagnosis, Section 8A.

Did you find a problem?