Hummer H1 (2006+). Manual - part 133

OBD-376

On-Board Diagnostics

_____________________________________________

Action Taken When the DTC Sets 

•

The transmission control module (TCM) illuminates the malfunction indicator lamp (MIL) during the second consecutive 

trip in which the Conditions for Setting the DTC are met. 

•    The transmission will lock in NEUTRAL. 

•    DTC P0876 will be stored in TCM history. 

•    The TCM freezes shift adapts. 

•    The TCM inhibits torque converter clutch (TCC) engagement. 

Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle com-
pletes 40 warm-up cycles without failure.

Diagnostic Aids 

•    Inspect the wiring for poor electrical connections at the TCM. Inspect 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, massage the wiring harness while watching the test equipment for a 

change.

•    You may have to drive the vehicle in order to experience a condition. 

•    This DTC could indicate a hydraulic leak path exhausting pressure from the reverse pressure switch. 

Step

Action

Value(s)

Yes

No

    1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to           

Diagnostic

System Check 

    2

Measure the transmission fluid level. Refer to Transmission Fluid
Checking Procedure.

Is the transmission fluid level correct?

Go to Step 3

Go to         

Transmission

Fluid Checking 

Procedure

    3

Measure the line pressure. 

Is the pressure within the specified value?

Go to Step 4

Go to        

Symptoms

Automatic

Transmission

_____________________________________________

 On-Board Diagnostics  OBD-377

5745804

    4

1.

Install the scan tool.

2.

Turn ON the ignition, with the engine OFF.

NOTE: Before clearing the DTC, use the scan tool in order to
record the Freeze Frame and Failure Records for reference. The
Clear Info function will erase the data.

3.

Record the DTC Freeze Frame and Failure Records.

4.

Clear the DTC.

5.

Start the engine.

6.

Using the scan tool, monitor TFP SW. R status.

Does the scan tool indicate TFP SW. R status is ON?

Go to     

Diagnostic Aids

Go to Step 5

    5

1.

Turn the ignition OFF.

2.

Disconnect C79 at the TCM.

3.

Install the J 39700 breakout box and the J 43799 breakout 
box adapter at C79.

4.

Connect C79 terminal 4 to a known good ground.

5.

Turn ON the ignition, with the engine OFF.

Does the scan tool indicate TFP SW. R status is ON when
grounded and OFF when open?

Go to Step 6

Go to Step 12

    6

1.

Turn the ignition OFF.

2.

Connect the C79 to the TCM.

3.

Disconnect the transmission 20-way connector C34.

4.

Turn the ignition ON. Additional DTCs might be set.

5.

Connect C34 terminal K to a known good ground.

Does the scan tool indicate TFP SW. R status is ON when
grounded and OFF when open?

Go to Step 7 

Go to Step 11

    7

1.

Remove the oil pan. Refer to Transmission Oil Pan Replace-
ment .

2.

Disconnect the AT internal wiring harness from the PSM and 
ground terminal D.

Does the scan tool indicate TFP SW. R status is ON when
grounded and OFF when open?

Go to Step 8 

Go to Step 10

    8

1.

Remove the PSM from the control valve body and leave the 
internal harness connected. 

2.

Provide a ground connection for the PSM to either the con-
trol valve body or the transmission main case.

3.

Using the eraser end of a pencil, push gently on the reverse 
pressure switch membrane.

Does the scan tool indicate TFP SW. R status is ON when
grounded and OFF when open?

Go to Diagnos-

tic Aids

Go to Step 9

    9

Replace the faulty PSM. 

Did you complete the replacement?

Go to Step 13 

    10

Replace the AT internal wiring harness. 

Did you complete the replacement?

Go to Step 13 

    11

Repair the wiring harness circuit 772 (DG) for an open or short. 

Did you complete the repair?

Go to Step 13 

Step

Action

Value(s)

Yes

No

OBD-378

On-Board Diagnostics

_____________________________________________

    12

NOTE: In most cases, the TCM is not at fault. Investigate thor-
oughly before replacing the TCM.

Replace the faulty TCM. 

Did you complete the replacement?

Go to Step 13 

    13

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Start the engine.

3.

Using the scan tool, monitor TFP SW. Reverse status.

4.

Select Specific DTC.

5.

Enter DTC P0876.

Has test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

No

_____________________________________________

 On-Board Diagnostics  OBD-379

5745804

DTC P0880 TCM Power Input Signal (Figure OBD-98)

Figure OBD-98:   TCM Power Input

Circuit Description

DTC P0880 will set if an abnormal power-down sequence has occurred. This condition means the transmission control module
(TCM) has lost battery positive voltage circuit, supply voltage, before it has finished saving information from that drive cycle. This
process is usually completed in less than 10 seconds.

DTC P0880 is a type C DTC.

Conditions for Setting the DTC

DTC P0880 sets during the next ignition cycle if the TCM loses TCM supply voltage less than 10 seconds after the ignition voltage
has been turned off.

Action Taken When the DTC Sets 

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

• DTC P0880 will be stored in TCM history. 

• Loss of adaptive information for drive cycle. Revert to previous adaptive settings. 

• The TCM inhibits torque converter clutch (TCC) engagement. 

Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle com-
pletes 40 warm-up cycles without failure.