Hummer H1 (2006+). Manual — part 97

OBD-232

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.

Apply and release the service brake.

Does the scan tool indicate that the brake switch is toggling off
and on?

Go to Diagnos-

tic Aids

Go to Step 3

3

1.

Turn OFF the ignition.

2.

Disconnect the C78 connector at the TCM.

3.

Install the J 39700 breakout box and the J 43799 breakout
box adapter.

4.

Turn ON the ignition.

5.

Using a DOMM, measure voltage at C78 pin 7 and a good
ground.

6.

Apply and release the service brake.

Is voltage within the specified value?

Brakes

applied 0.0

Volts

Brakes

released

12.0 Volts

Go to Diagnos-

tic Aids

Go to Step 4

4

Using the DVOM, measure voltage at terminal C of the stop lamp
switch and a good ground.

Is voltage within the specified value?

B+

Go to Step 5

Go to Step 6

5

Using a DVOM, measure voltage at terminal D of the stop lamp
switch.

Is voltage available?

B+

Go to Step 8

Go to Step 7

6

1.

Remove the brake fuse.

2.

Inspect the brake fuse for an open.

Did you find and correct the condition?

Go to Step 9

7

Repair or replace the stop lamp switch.

Did you complete the repair or replacement?

Go to Step 9

8

Inspect the engine wiring harness for an open or short to ground.

Did you find and correct the condition?

Go to Step 9

9

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Using the scan tool, monitor the brake switch.

3.

Operate the vehicle under the Conditions for Setting the
DTC.

4.

Select Specific DTC.

5.

Enter DTC P0703.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

No

_____________________________________________

On-Board Diagnostics OBD-233

5745804

DTC P0708 Transmission Range Sensor Circuit High Input (Figure OBD-65)

Figure OBD-65: Transmission Range Sensor Circuit

Circuit Description

The installation of a transmission mounted neutral start back up (NSBU) switch is required. This switch mounts directly onto the
transmission housing from the outside, and detects the angular position of the shift selector shaft. This position is communicated to
the transmission control module (TCM) so that certain vehicle control functions can be coordinated with the position of the shift
controls. The NSBU switch has redundant circuitry to alert the TCM in the event of a single wire or switch failure.

The neutral signal output of the NSBU switch is typically used as confirmation that the transmission is in NEUTRAL before the
engine starter is engaged. The NSBU switch is interfaced to the starter circuit with weatherproof electrical connectors. The reverse
signal provision may be used to activate vehicle back-up lights and/or reverse warning devices.

DTC P0708 is a type A DTC.

OBD-234

On-Board Diagnostics

_____________________________________________

Conditions for Setting the DTC

DTC P0708 sets when the TCM detects an invalid condition and parity error occurring over consecutive ignition cycles.

Action Taken When the DTC Sets

While diagnostic response is active, one of the following conditions can occur:

• The TCM illuminates the malfunction indicator lamp (MIL).

• The transmission fails to hydraulic default.

• DTC P0708 will be stored in TCM history.

• The TCM freezes shift adapts.

• TCM inhibits torque converter clutch (TCC) engagement.

Conditions for Clearing the DTC

A scan tool must be used to clear the code from TCM history. This DTC does not automatically clear from TCM history after 40
ignition cycles.

Diagnostic Aids

• Inspect the wiring for poor electrical connections at the TCM and the ECM. 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.

• If a P0875, previously a P1713, is shown in failure records as being set first on the failure list followed by a P0872, previ-

ously a P1711, combined with P0708, this generally indicates a PNP internal switch failure. Often when the DTCs are
cleared they do not return, this may be due to moisture that was present at the time the DTC was set, causing a short in-
ternally.

• Inspect the NSBU switch linkage carefully for proper adjustment. Also, inspect the switch for signs of damage.

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

Inspect for proper adjustment of the NSBU switch.

Is the NSBU switch and shift linkage properly adjusted?

Go to Step 3

_____________________________________________

On-Board Diagnostics OBD-235

5745804

3

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.

With the scan tool, observe the TR Sw. display while select-
ing each transmission range: P, R, N, D4, D3, D2, and D1.

Does each selected transmission range match the scan tool TR
Sw. display?

Go to Diagnos-

tic Aids

Go to Step 4

4

1.

Turn the ignition OFF.

2.

Disconnect the 12-way connector at the NSBU switch.

3.

Turn the ignition ON.

4.

In sequence, connect terminals 4, 5, 6, and 8 to terminal 7 in
the 12-way NSBU connector.

5.

Using the scan tool, monitor transmission range switch sta-
tus.

Does each selected transmission range match the scan tool NSBU
Sw. display?

PARK = 5

and 8

REVERE

= 5 and 4

NETRAL

= 8 and 4

DRIVE 4
= 6 and 4

DRIVE 3

= 4, 5, 6, 8

DRIVE 2
= 5 and 6

DRIVE 1
= 6 and 8

Go to Step 8

Go to Step 5

5

Using the DVOM and the J 35616-C GM terminal test kit mea-
sure the following:

1.

Measure the voltage from pin 5 of the NSBU switch 12-way
connector to ground.

2.

Measure the voltage from pin 6 of the NSBU switch 12-way
connector to ground.

3.

Measure the voltage from pin 8 of the NSBU switch 12-way
connector to ground.

4.

Measure the voltage from pin 4 of the NSBU switch 12-way
connector to ground.

Does the voltage measure within the specified value at all four
terminals?

B+

Go to Step 6

Go to Step 7

Step

Action

Value(s)

Yes

No