Hummer H1 (2006+). Manual — part 109
OBD-280
On-Board Diagnostics
_____________________________________________
DTC P0741 Torque Converter Clutch System Stuck Off
Circuit Description
The transmission control module (TCM) uses data from the engine speed sensor and the input speed sensor (ISS) to calculate
torque converter slip value. The TCM then compares this calculated slip value to a preset value in the TCM calibration.
DTC P0741 is a type B DTC.
Conditions for Setting the DTC
DTC P0741 sets when the TCM detects one of the following conditions:
• A TCC slip value greater than 80 RPM for 15 seconds.
• The TCC slip speed values indicate a stuck off state.
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 P0741 will be stored in TCM history.
• The TCM freezes shift adapts.
• The TCM inhibits 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.
Step
Action
Value(s)
Yes
No
1
NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used
Was the “On-Board Diagnostic (OBD) System Check” per-
formed?
Go to step 2.
Go to OBD Sys-
tem Check.
_____________________________________________
On-Board Diagnostics OBD-281
5745804
2
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.
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.
Drive the vehicle under normal operating conditions.
2.
Using the scan tool, monitor converter slip speed indicated
when a range is attained where the TCC should be applied.
Is the slip speed value at or greater than the specified value when
the TCC should be applied?
80 RPM
Go to Step 4
Go to Diagnos-
tic Aids
4
This condition indicates the TCC is mechanically stuck OFF. In-
spect for the following conditions:
• Worn TCC clutch
• Faulty torque converter clutch pulse width modulated
(TCC PWM) solenoid
• Debris in the TCC valve bore
• Clogged converter relief passage
Did you find and repair a condition?
Go to Step 5
5
Perform the following procedure in order to verify the repair:
1.
Clear the DTC.
2.
Start the engine.
3.
Using the scan tool, operate the vehicle under normal operat-
ing conditions.
4.
Select Specific DTC.
5.
Enter DTC P0741.
Has the test run and passed?
System OK
Go to Step 1
Step
Action
Value(s)
Yes
No
OBD-282
On-Board Diagnostics
_____________________________________________
DTC P0742 Torque Converter Clutch System Stuck On
Circuit Description
The transmission control module (TCM) uses data from the engine speed sensor and the input speed sensor (ISS) to calculate the
torque converter slip value. The TCM then compares this calculated slip value to a preset value in the TCM calibration.
DTC P0742 is a type B DTC.
Conditions for Setting the DTC
DTC P0742 sets when the TCM detects TCC slip speed values indicating a stuck on or locked condition for 2.5 seconds.
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.
• If failure occurs before shifting is completed, the transmission will shift to NEUTRAL. If failure occurs while shifting is
being completed, the transmission will shift to NEUTRAL or 1st range 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 NEUTRAL or REVERSE.
• If the shift selector is returned to DRIVE, the transmission will shift to NEUTRAL or 1st range.
• DTC P0742 will be stored in TCM history.
• The TCM inhibits TCC engagement.
• The TCM freezes shift adapts.
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.
Step
Action
Value(s)
Yes
No
1
NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used
Was the “On-Board Diagnostic (OBD) System Check” per-
formed?
Go to step 2.
Go to OBD Sys-
tem Check.
_____________________________________________
On-Board Diagnostics OBD-283
5745804
2
1.
Install the scan tool.
2.
Set the parking brake and block the wheels to prevent vehicle
movement.
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 Failures Records.
4.
Clear the DTC.
5.
Start the engine.
6.
Apply the vehicle brakes and select DRIVE.
Did the engine stall?
Go to Step 3
Go to Diagnos-
tic Aids
3
1.
Remove the transmission oil pan.
2.
Inspect for contaminated fluid and/or excessive material in
the pan.
Is the fluid contaminated or excessive material found in the pan?
Go to Step 5
Go to Step 4
4
This condition indicates the TCC is mechanically stuck ON. In-
spect for the following conditions:
1.
Faulty torque converter clutch pulse width modulated (TCC
PWM) solenoid
2.
Stuck or sticking TCC valve
3.
Restricted transmission cooler lines
Did you find and repair a condition?
Go to Step 6
5
Remove the transmission for overhaul or replacement.
Did you complete the repair or replacement?
Go to Step 6
6
Preform the following procedure in order to verify the repair:
1.
Clear the DTC.
2.
Drive the vehicle under normal operating conditions.
3.
Using the scan tool, monitor TCC slip speed. The TCC must
engage/disengage when commanded.
4.
Select Specific DTC.
5.
Enter DTC P0742.
Has the test run and passed?
System OK
Go to Step 1
Step
Action
Value(s)
Yes
No
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