Hummer H1 (2006+). Manual — part 96

OBD-228

On-Board Diagnostics

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DTC P0700 Transmission Control Module (TCM) Request Mill Illumination

Circuit Description

This diagnostic trouble code (DTC) indicates that a related transmission DTC set in the transmission control module (TCM). The
engine control module (ECM) receives the TCM DTC information over the serial data circuit. The ECM turns ON the malfunction
indicator lamp (MIL) when the TCM sends a message over the serial data circuit requesting MIL illumination.

DTC P0700 is a type A DTC.

Conditions for Setting the DTC

The ECM receives a serial data message from the TCM, in order to illuminate the MIL.

Action Taken When the DTC Sets

• The control module illuminates the MIL when the diagnostic runs and fails.

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this informa-

tion in the Freeze Frame/Failure Records.

Conditions for Clearing the DTC

• The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle

completes 40 warm-up cycles without failure.

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.

2

1.

Install the scan tool.

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.

• DTC P0700 is set by the ECM. DTC P0700 allows a tech-

nician to be alerted from the engine diagnostic side that
the TCM is setting a DTC and is requesting the MIL.

• If the TCM has DTC's set that are requesting MIL illumi-

nation, those DTC's must be diagnosed first. Refer to
Obtaining Diagnostic Trouble Codes.

2.

Turn ON the ignition, with the engine OFF.

Does the scan tool display any DTC's other than DTC P0700?

Go to Diagnos-

tic Trouble

Code (DTC)

List/Type

Go to Diagnos-

tic System

Check - Vehicle

in Vehicle DTC

Information

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On-Board Diagnostics OBD-229

5745804

DTC P0701 Transmission Control System

Circuit Description

The transmission control module (TCM) monitors the status of the pressure switches at start-up to detect the presence of hydraulic
pressure.

DTC P0701 is a type C DTC.

Conditions for Setting the DTC

DTC P0701 sets when the TCM detects the following conditions:

• Transmission fluid temperature is above -25°C (-13°F).

• All pressure switches do not indicate pressure at startup.

• Engine speed is above 500 RPM for 6 seconds or 400 RPM for 15 seconds.

• Forward or REVERSE range is selected.

Action Taken When the DTC Sets

• he TCM does not illuminate the malfunction indicator lamp (MIL).

• DTC P0701 will be stored in TCM history.

• 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.

•

DTC P0701 may be logged if a forward or REVERSE range is selected immediately after the engine is started, and before

the TCM detects pressure at the switches, 2-6 seconds after engine start.

• A plugged control main filter may cause this code to set.

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.

OBD-230

On-Board Diagnostics

_____________________________________________

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.

Start the engine and measure the transmission fluid level.
Refer to Transmission Fluid Checking Procedure.

Is the transmission fluid level correct?

Go to Step 3

Go to Step 4

3

This DTC can be set after performing fluid service and filter
change, after replacement of the pressure switch manifold (PSM),
or after a long period of storage.

Have any of these conditions occurred?

Go to Step 7

Go to Step 5

4

Add fluid to the proper level.

Is the fluid at the appropriate level?

Go to Step 5

5

Measure line pressure.

Is the pressure within the specified value?

Go to Step 7

Go to Step 6

6

No main pressure at idle may be an indication of the following
conditions:

• Stuck or sticking lube regulator valve

• Stuck or sticking main regulator valve

• Loose or damaged suction filter

• Defective suction filter seal

Did you find the reason for a no line pressure condition and was it
repaired?

Go to Step 7

Go to Symp-

toms - Auto-

matic

Transmission

7

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Start the engine.

3.

Select Specific DTC.

4.

Enter DTC P0701.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

No

_____________________________________________

On-Board Diagnostics OBD-231

5745804

DTC P0703 Brake Switch Circuit

Circuit Description

A mechanical switch attached to the brake pedal sends a signal to the transmission control module (TCM) indicating the service
brake has been applied.

DTC P0703 is a type C DTC.

Conditions for Setting the DTC

DTC P0703 sets when the vehicle accelerates 10 times with the brake switch in the ON position, or decelerates 10 times with the
brake switch in the OFF position.

Action Taken When the DTC Sets

• The TCM does not illuminate the malfunction indicator lamp (MIL).

• The TCM uses default assumption that brake is off.

• DTC P0703 will be stored in TCM history.

• 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

DTC P0703 indicates that the TCM did not see the proper input signal for service brake status during an acceleration or decelera-
tion cycle. This may indicate an open or short in the TCC brake switch/cruise control release circuit or a faulty stop lamp switch.

• 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.