Hummer H2. Manual - part 2484

DTC P0748 

steady acceleration, with a TP angle at 
20%.  

While the scan tool TCC Enable status is NO, 
does the scan tool display a TCC Slip Speed 
within the specified range?

Go to Step 3

Go to Diagnostic 

Aids

3

The TCC is hydraulically stuck ON. Inspect 
for the following: 

z

Clogged exhaust orifice in the TCC 
solenoid valve.  

z

Converter clutch apply valve stuck in the 
apply position.  

z

Misaligned or damaged valve body 
gasket.  

z

Restricted release passage.  

z

Restricted transmission cooler line.  

 
Did you find and correct the condition?

-

Go to Step 4

-

4

Perform the following procedure in order to 
verify the repair: 

1. Select DTC.  

2. Select Clear Info.  

3. Drive the vehicle in D4 with the TCC 

OFF and the throttle above 17%. Ensure 
that the scan tool TCC Slip Speed is 
100-2,000 RPM for 5 seconds.  

4. Select Specific DTC.  

5. Enter DTC P0742.  

 
Has the test run and passed?

-

Go to Step 5

Go to Step 2

5

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 - 

6.0L (LQ4)

System OK

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2

 

Fig. 13: Pressure Control (PC) Solenoid Valve Diagram 
Courtesy of GENERAL MOTORS CORP. 

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) 

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2

 

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 position sensor voltage, the 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 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 

z

The PCM does not illuminate the malfunction indicator lamp (MIL).  

z

The PC solenoid valve is OFF.  

z

The PCM freezes transmission adaptive functions.  

z

The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM 
stores this information as Failure Records.  

z

The PCM stores DTC P0748 in PCM history.  

Conditions for Clearing the DTC 

z

A scan tool can clear the DTC.  

z

The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-
emission-related diagnostic fault occurring.  

z

The PCM cancels the DTC default actions when the fault no longer exists and/or 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. 

2: This step tests the ability of the PCM to command the PC solenoid valve.  

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2

 

3: This step tests the PC solenoid valve and automatic transmission 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 - 

6.0L (LQ4)

2

1. With a scan tool.  

2. Turn ON the ignition, with the engine 

OFF. 

3. Record the DTC Failure Records.  

4. Clear the DTC.  

5. Start the engine.  

6. 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?

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.

0.16 
amp

Go to Intermittent 

Conditions in 

Engine Controls - 

6.0L (LQ4)

Go to Step 3

3

1. Turn OFF the ignition.  

2. Disconnect the AT inline 20-way 

connector.  

3. Install the J 44152 Jumper Harness (20 

pins) on the transmission side of the AT 
inline 20-way connector.  

4. Using the DMM and the J 35616 GM 

Terminal Test Kit, measure the resistance 
between terminals C and D of the J 
44152 . 

Refer to Automatic Transmission 

3-7 

ohm

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2