Hummer H1 (2006+). Instruction - page 116
OBD-308
On-Board Diagnostics
_____________________________________________
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 28 and terminal 31.
5.
Turn ON the ignition, with the engine OFF.
6.
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
4
1.
Turn the ignition OFF.
2.
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
5
1.
Turn the ignition OFF.
2.
Connect the C79 at the TCM.
3.
Disconnect the wiring harness from the transmission 20-way
connector C34.
4.
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
6
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
7
1.
Remove the transmission oil pan.
2.
Remove the AT internal wiring harness at the shift solenoid
E connector.
3.
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
8
Replace the AT internal wiring harness.
Did you complete the replacement?
Go to Step 11
9
Replace the faulty shift solenoid E.
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 P0773.
Has the test run and passed?
System OK
Go to Step 1
Step
Action
Value(s)
Yes
No
_____________________________________________
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
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.
Is the transmission fluid level correct?
Go to Step 3
Go to
Transmission
Fluid Checking
Procedure
3
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 Records.
4.
Clear the DTC.
5.
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
4
1.
Start the engine.
2.
Drive the vehicle under normal operating conditions.
3.
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
5
1.
Connect a 2,000 kPa (300 psi) pressure gage to the line pres-
sure tap.
2.
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
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
7
1.
Remove the transmission oil pan. Refer to Automatic Trans-
mission Fluid/Filter Replacement.
2.
Inspect for signs of clutch failure.
Are there signs of clutch failure?
Go to Step 8
Go to Step 9
8
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
9
Inspect for a stuck or sticking PC valve B.
Did you find and correct a condition?
Go to Step 11
Go to Step 10
10
Replace the faulty PC solenoid B.
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.
Start the engine.
3.
Use the scan tool to reset adaptive values for all shifts.
4.
Operate the vehicle in all ranges under normal driving condi-
tions.
5.
Select Specific DTC.
6.
Enter DTC P0776.
Has test run and passed?
System OK
Go to Step 1
Step
Action
Value(s)
Yes
No
