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Hummer H1 (2006+). Manual - part 116

OBD-308

On-Board Diagnostics

_____________________________________________

Turn the ignition OFF.

Disconnect the C79 at the TCM.

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

Using a DVOM, measure voltage between connector C79
terminal 28 and terminal 31.

Turn ON the ignition, with the engine OFF.

Using the scan tool, command E solenoid to ON.

Is the voltage within the value specified when E solenoid is com-
manded ON?

B+

Go to Step 4

Go to Step 10

Turn the ignition OFF.

Using a DVOM, measure the resistance between connector
C79 terminal 28 and terminal 31 harness side.

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

Turn the ignition OFF.

Connect the C79 at the TCM.

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

Install a DVOM and measure resistance on the transmission
side of C34 terminals W and C.

Is the resistance within the value specified?

22.0 ohms

[commat]

20°C

(68°F)

Go to Step 6

Go to Step 7

Inspect the wiring harness from C34 to C79 circuits 782 (TN) and
779 (GY) for an open or short to ground.

Did you find and correct the condition?

Go to Step 11

Remove the transmission oil pan.

Remove the AT internal wiring harness at the shift solenoid
E connector.

Using the DVOM, measure the resistance of shift solenoid E.

Is the solenoid resistance within the specified value?

22.0 ohms

[commat]

20°C

(68°F)

Go to Step 8

Go to Step 9

Replace the AT internal wiring harness.

Did you complete the replacement?

Go to Step 11

Replace the faulty shift solenoid E.

Did you complete the replacement?

Go to Step 11

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

Perform the following procedure in order to verify the repair:

Clear the DTC.

Drive the vehicle under normal operating conditions.

Select Specific DTC.

Enter DTC P0773.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

_____________________________________________

On-Board Diagnostics OBD-309

5745804

DTC P0776 Pressure Solenoid B Controlled Clutch Stuck Off

Circuit Description

Pressure control (PC) solenoid B is used to control oncoming, off-going, and holding pressure in any one of five clutches. This so-
lenoid is referred to as a pressure proportional to current (PPC) solenoid since the output hydraulic pressure supplied by this sole-
noid is proportional to the controlled current command.

The transmission control module (TCM) uses information from the turbine and output speed sensors to detect if a clutch is slip-
ping. The clutch being controlled by PC solenoid B will vary depending on the shift that was being completed.

DTC P0776 is a type A DTC.

Conditions for Setting the DTC

DTC P0776 sets when the TCM detects an incorrect oncoming ratio, during a forward range shift, for an accumulated number of
occurrences.

Action Taken When the DTC Sets

• The TCM illuminates the malfunction indicator lamp (MIL)

• When failure occurs in a forward range, the transmission will go to the previous range. If failure occurs in NEUTRAL or

REVERSE, the transmission will lock in NEUTRAL while diagnostic response is active.

• If the shift selector is moved to NEUTRAL, the transmission will shift to NEUTRAL and in some cases, may lock in

NEUTRAL.

• If the shift selector is moved to REVERSE, the transmission will shift to REVERSE or NEUTRAL.

• If the shift selector is returned to a forward range and the transmission is compromised by over speeding or direction

change, the transmission will shift to NEUTRAL.

• DTC P0776 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 indicates the oncoming clutch, being controlled by PC solenoid B, is not applied or applied too slowly. This

could indicate a leak or obstruction in a specific clutch apply circuit. Observe scan tool failure record data for previous or
current range information when the DTC was set, to determine specific shift when the DTC was set. Refer to Solenoid
and Clutch Chart to determine which clutch circuit is suspect.

OBD-310

On-Board Diagnostics

_____________________________________________

NOTE:

Important: Clutch failure due to installation of an engine power upgrade is not covered under the transmission manufac-

turers warranty.

Inspect for the presence of an add-on engine power package. When engine horsepower or torque is increased over factory rating, a
shift flare condition may occur.

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to

Diagnostic

System Check

Measure the transmission fluid level.
Is the transmission fluid level correct?

Go to Step 3

Go to

Transmission

Fluid Checking

Procedure

Install the scan tool.

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.

Record the DTC Freeze Frame and Failure Records.

Clear the DTC.

Using the scan tool, measure ignition voltage.

Is the voltage within the specified range?

9-18 Volts

Go to Step 4

Go to DTC

P0562 for low

voltage or DTC

P0563 for high

voltage

Start the engine.

Drive the vehicle under normal operating conditions.

Using the scan tool, monitor engine, turbine and output
speed sensor readings.

Is speed sensor data erratic?

Go to the

appropriate

speed sensor

DTC

Go to Step 5

Connect a 2,000 kPa (300 psi) pressure gage to the line pres-
sure tap.

Use the scan tool, in Clutch Test Mode, to cycle through all
transmission ranges with the engine at idle and vehicle
brakes applied. Record line pressure in each range.

Was the line pressure low in a specific range or in ranges where
the same clutch was applied?

Go to Low Main

Line Pressure in

All Ranges

Go to Step 6

Refer to Transmission Stall Test.

Conduct a clutch test for all forward ranges.

Did the turbine speed remain at zero in all ranges?

Go to Diagnos-

tic Aids

Go to Step 7

Remove the transmission oil pan. Refer to Automatic Trans-
mission Fluid/Filter Replacement.

Inspect for signs of clutch failure.

Are there signs of clutch failure?

Go to Step 8

Go to Step 9

Remove the transmission for overhaul or replacement. Refer to
Transmission Replacement.

Did you complete the repair or replacement?

Go to Step 11

_____________________________________________

On-Board Diagnostics OBD-311

5745804

Inspect for a stuck or sticking PC valve B.

Did you find and correct a condition?

Go to Step 11

Go to Step 10

Replace the faulty PC solenoid B.

Did you complete the replacement?

Go to Step 11

Perform the following procedure in order to verify the repair:

Clear the DTC.

Start the engine.

Use the scan tool to reset adaptive values for all shifts.

Operate the vehicle in all ranges under normal driving condi-
tions.

Select Specific DTC.

Enter DTC P0776.

Has test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

Content .. 114 115 116 117 ..