Hummer H1 (2006+). Manual - part 117

OBD-312

On-Board Diagnostics

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DTC P0777 Pressure Solenoid B Controlled Clutch Stuck On

Circuit Description

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

The transmission control module (TCM) uses information from the turbine speed sensor and output speed sensor (OSS) to detect if
a clutch is in a tie-up condition or 3 clutches are applied. The clutch being controlled by PC solenoid B will vary depending on the
shift being made.

DTC P0777 is a type A DTC

Conditions for Setting the DTC

DTC P0777 sets when the TCM detects the off-going clutch, controlled by PC solenoid B, remains engaged during a forward range
shift.

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.

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

lock in 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 P0777 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 off-going clutch, being controlled by PC solenoid B, is not releasing or is slow to release. This could

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

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On-Board Diagnostics OBD-313

5745804

NOTE: Clutch failure due to installation of an engine power upgrade is not covered under the transmission manufacturers war-
ranty.

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. Refer to Transmission Fluid
Checking Procedure.

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 turbine speed remain at zero in all ranges?

Go to

Diagnostic 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 a 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

OBD-314

On-Board Diagnostics

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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 P0777.

Has test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

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On-Board Diagnostics OBD-315

5745804

DTC P0778 Pressure Solenoid B Electrical (Figures OBD-81, and 82)

Figure OBD-81: External Fuse Box Circuit

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