Hummer H1 (2006+). Manual - part 156

OBD-468

On-Board Diagnostics

_____________________________________________

    3

Select 4HI followed by 4LO using the transfer case selector.

Does the scan tool indicate 4WD low status as YES for both se-
lector positions?

Go to Step 4

Go to Step 9

    4

Remove the connector at the transfer case selector.

Does the scan tool indicate 4WD low status as YES?

Go to Step 5

Go to Step 7

    5

Inspect 4WD Low signal circuit for a short to ground.

Did you find a condition?

Go to Step 6

Go to Step 15

    6

Inspect and repair the short to ground in 4WD Low signal circuit. 

Did you complete the repair?

Go to Step 16 

    7

Inspect the transfer case switch for proper operation or a short to
ground.

Did you find a condition?

Go to Step 8

Go to Step 15

    8

Replace the faulty transfer case switch. 

Did you complete the replacement?

Go to Step 16 

    9

Using the transfer case selector, select 4HI followed by 4LO.

Does the scan tool indicate 4WD Low status as NO for both se-
lector positions?

Go to Step 10 

Go to Step 15

    10

1.

Remove the connector at the transfer case switch.

2.

Ground 4WD Low signal circuit to a known ground.

Does the scan tool indicate 4WD low status as NO?

Go to Step 11 

Go to Step 13

    11

Inspect the short to ground in the brake switch signal circuit. 

Did you find a condition?

Go to Step 12 

Go to Step 15

    12

Repair the open condition in the 4WD Low signal circuit. 

Did you complete the repair?

Go to Step 16 

    13

Inspect the transfer case switch for an open condition.

Did you find an open condition?

Go to Step 14

Go to Step 15

    14

Replace the faulty transfer case switch. 

Did you complete the replacement?

Go to Step 16

    15

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 16

    16

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Drive the vehicle under normal operating conditions. Moni-
tor the 4WD Low status with the scan tool. The 4WD Low 
status must indicate NO when 4WD HI is selected, and YES 
when 4WD LO is selected.

3.

Select Specific DTC. 

4.

Enter DTC P2771.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

No

_____________________________________________

 On-Board Diagnostics  OBD-469

5745804

DTC P2810 Solenoid G Electrical (Figure OBD-119)

Figure OBD-119:   Solenoid G Circuit

Circuit Description

G solenoid is a normally-closed (N/C) solenoid used to modulate the transmission main pressure. Under specific conditions, low
throttle setting, low engine torque, low engine speed, and low transmission output speeds, the transmission control module (TCM)
commands the G solenoid on.

When G solenoid is applied, fluid is routed to the main pressure regulator valve; this in turn reduces the main pressure schedule and
improves the volume of oil through the overage circuit. By modulating main pressure, cooler flow at idle can be increased allowing
improved cooling and reducing transmission pump noise.

Conditions for Setting the DTC

DTC P2810 is set when the TCM detects an open circuit, short to ground, or short to power at G solenoid circuit for greater than 2
seconds.

OBD-470

On-Board Diagnostics

_____________________________________________

Action Taken When the DTC Sets 

•    The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions 

for Setting the DTC are met. 

•    DTC P2810 will be stored in TCM history. 

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. 

•    Solenoids are sensitive to battery voltage spikes and poor ground connections. 

Step

Action

Value(s)

Yes

No

    1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnos-

tic System 

Check

    2

1.

Install the scan tool.

2.

Start the engine.

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 Record Records.

4.

Clear the DTC.

5.

Using the scan tool, observe ignition voltage.

Is the voltage within the specified range?

9-18 Volts

Go to Step 3

Go to DTC 

P0562 for low 

voltage or DTC 

P0563 for high 

voltage

    3

1.

Turn the ignition OFF.

2.

Disconnect the C79 at the TCM.

3.

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

4.

Using a DVOM, measure voltage between connector C79 
terminal 30 and terminal 32.

5.

Turn the ignition ON, with the engine OFF.

6.

Using the scan tool, command G solenoid to ON.

Is the voltage within the specified value when G solenoid is com-
manded ON.

B+

Go to Step 4

Go to Step 10

_____________________________________________

 On-Board Diagnostics  OBD-471

5745804

    4

1.

Turn the ignition OFF.

2.

Using a DVOM, measure the resistance between connector 
C79 terminal 30 and terminal 32.

Is the resistance reading within the specified value?

22.0 ohms 

[commat]

20°C

(68°F)

Go to Diagnos-

tic Aids

Go to Step 5

    5

1.

Turn the ignition OFF.

2.

Connect the C79 at the TCM.

3.

Disconnect the wiring harness from the transmission 20-way 
C34.

4.

Using a DVOM, measure resistance on the transmission side 
of the 20-way connector terminals R and S.

Is the resistance within the specified value?

22.0 ohms 

[commat]

20°C

(68°F)

Go to Step 6

Go to Step 7

    6

Inspect the wiring harness circuit for an open or short to ground
between C34 and C79. 

Did you find and correct a condition?

Go to Step 11 

    7

1.

Connect the transmission 20-way C34.

2.

Remove the oil pan. 

3.

Remove the AT internal wiring harness at G solenoid con-
nector.

4.

Using a DVOM, measure the resistance of G solenoid.

Is the solenoid resistance within the specified value?

22.0 ohms 

[commat]

20°C

(68°F)

Go to Step 8

Go to Step 9

    8

Replace the faulty AT internal wiring harness. 

Did you complete the replacement?

Go to Step 11

    9

Replace the faulty G solenoid. 

Did you complete the replacement?

Go to Step 11

    10

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 11 

    11

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Drive the vehicle under normal operating conditions.

3.

Select Specific DTC.

4.

Enter DTC P2810.

Has the test run and passed?

System OK 

Go to Step 1

Step

Action

Value(s)

Yes

No