Hummer H1 (2006+). Manual - part 110

OBD-284

On-Board Diagnostics

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DTC P0743 Torque Converter Clutch (Figure OBD-75)

Figure OBD-75: Torque Converter Clutch Circuit

Circuit Description

The torque converter clutch (TCC) solenoid is a pulse width modulated (PWM) solenoid. Pulse width modulation occurs when the
signal from the transmission control module (TCM) to a solenoid is modulated at an established frequency, causing the steel check
ball in the solenoid to rapidly open and close the solenoid passage. This serves to vary the output fluid pressure.

DTC P0743 is a type B DTC.

Conditions for Setting the DTC

DTC P0743 sets when the TCM detects an open circuit, a short to power, or a short to ground in the TCC PWM solenoid circuit for
1.5 seconds.

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On-Board Diagnostics OBD-285

5745804

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 P0743 will be stored in TCM history.

• The TCM inhibits TCC engagement.

• The TCM freezes shift adapts.

• REVERSE operation is disabled.

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. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• 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

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.

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 refer-
ence. The Clear Info function will erase the data.

• This diagnostic table should only be used if the DTC is

currently failing. If the DTC is not active, refer to Test-
ing for Intermittent Conditions and Poor Connections
in Wiring Systems until the DTC becomes active.

Record the DTC Freeze Frame and Failure Records.

Clear the DTC.

Using the scan tool, measure ignition voltage.

Is 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

OBD-286

On-Board Diagnostics

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Turn the ignition OFF.

Disconnect the C79 connector at the TCM.

Using a DVOM, measure the resistance between connector
C79 terminal 29 and connector C79 terminal 32.

Is the resistance reading within the specified value?

10.5 ohms

[commat]

20° (68°F)

Go to Step 4

Go to Step 5

Turn the ignition OFF.

Disconnect the TCM connector C79.

Install the J 39700 breakout box and the J 43799 breakout
box adapter. Do not connect the vehicle side C79 connector
to the J 43799.

Using a 12-volt unpowered test light, place the leads on ter-
minals 29 and 32 of the J 39700.

Turn the ignition ON, with the engine OFF.

Use the scan tool in Solenoid Test Mode to command the
TCC PWM solenoid ON and OFF.

Does the test lamp turn ON and OFF when commanded?

Go to Diagnos-

tic Aids

Go to Step 11

Turn the ignition OFF.

Connect the C79 connector to the TCM.

Disconnect the transmission 20-way connector.

Turn the ignition ON, with the engine OFF. Additional DTCs
may set.

Using a 12-volt unpowered test light, place the leads at C34
harness side terminals J and S.

Use the scan tool in Solenoid Test Mode to command the
TCC PWM solenoid ON and OFF.

Does the test lamp turn ON and OFF when commanded?

Go to Step 6

Go to Step 8

Turn the ignition OFF.

Using a DVOM, measure the resistance between terminals J
and S of C34.

Is the solenoid resistance within the specified value?

10.5 ohms

[commat]

20°C

(68°F)

Go to Diagnos-

tic Aids

Go to Step 7

Remove the oil pan. Refer to Oil Pan Replacement.

Remove the internal wiring harness at the TCC PWM sole-
noid connector.

Using a DVOM, measure the resistance of the TCC PWM
solenoid between pins B and A.

Is the solenoid resistance within the specified value?

10.5 ohms

[commat]

20°C

(68°F)

Go to Step 9

Go to Step 10

Repair the engine wiring harness.

Did you complete the repair

Go to Step 12

Replace the faulty AT internal wiring harness.

Did you complete the replacement?

Go to Step 12

Replace the faulty TCC PWM solenoid.

Did you complete the replacement?

Go to Step 12

Step

Action

Value(s)

Yes

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On-Board Diagnostics OBD-287

5745804

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 12

Perform the following procedure in order to verify the repair:

Clear the DTC.

Drive the vehicle under normal operating conditions.

Using the scan tool, monitor TCC slip speed. The TCC must
engage/disengage when commanded.

Select Specific DTC.

Enter DTC P0743.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

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