Hummer H1 (2002+). Manual - part 69

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Transmission/Transfer Case 5-75

05745159

Turn the ignition OFF.

Disconnect the OSS Sensor connector from the
OSS Sensor.

Connect a J– 39200 DVOM (covered in Electrical
Section 12) on AC Voltage scale between terminals
A and B at the OSS Sensor.

Turn the ignition to the RUN position, and start the
engine.

Place the transmission in D3 range.

With the wheels rotating, slowly accelerate to 2000
engine RPM and hold.

Does the voltage drop or fluctuate at 2000 RPM?

—

Go to Step 17

Go to Step 4

Turn the ignition OFF.

Reconnect the OSS sensor harness to the sensor.

Disconnect the VSS Buffer Module harness con-
nector from the component.

Turn the ignition ON and turn the engine OFF.

Set the J– 39200 DVOM on AC volts.

Connect the J– 39200 DVOM between terminals 7
and 12 of the VSS Buffer Module harness connec-
tor.

Start the engine.

Place the transmission in D3 range.

With the wheels rotating, slowly accelerate to 2000
engine RPM and hold steady.

Does the voltage drop or fluctuate at 2000 RPM?

Above 0.5 volts

Go to Step 5

Go to Step 7

Inspect circuit 821 and circuit 822 for an intermittent
Did you find a problem?

Go to Step 12

Go to Step 6

Inspect circuit 821 and circuit 822 for an intermittent
short together or a short to ground.
Did you find a problem?

Go to Step 12

With the engine OFF, turn the ignition switch ON.
Select DC volts, and inspect for ignition voltage at ter-
minal 9 of the VSS Buffer Module harness.
Is the voltage greater than the specified value?

10.5 volts DC

Go to Step 9

Go to Step 8

Repair the intermittent open or high resistance in circuit
39.
Is the repair complete?

Go to Step 21

Connect the J– 39200 DVOM between terminals 8
and 9 of the VSS Buffer Module harness connector.
Set the DVOM on DC volts.

Turn the ignition to the Run position.

Is the voltage greater than the specified value?

10.5 volts DC

Go to Step 11

Go to Step 10

Repair the open or high resistance in circuit 451.
Is the repair complete?

Go to Step 21

DTC P0723 Output Speed Sensor Intermittent (Cont’d)

Step

Action

Value

Yes

5-76

Transmission/Transfer Case

_____________________________________________

With the engine OFF, turn the ignition to the RUN
position.

Using the J– 39200 DVOM, measure the voltage at
the VSS Buffer Harness connector terminal 13.

Is the voltage steady and within the specified voltage?

4.8-5.2 volts

Go to Step 13

Go to Step 14

Repair the short in circuit 821 and circuit 822. Refer to
Electrical Diagnosis, Section 8.
Did you correct the problem?

Go to Step 21

Turn the ignition to the OFF position.

Reconnect the VSS Buffer Module harness to the
VSS Buffer Module.

Set the J– 39200 DVOM on the DC volts scale.

Back probe terminal 13 of the VSS Buffer Harness
connector with the
J– 39200 DVOM.

Start the engine.

Place the transmission in a D3 range.

With the wheels rotating, slowly accelerate the
engine to 2000 RPM and hold.

Is the voltage reading steady within the specified value?

1.5-3.5 volts

Go to Step 19

Go to Step 18

Is the voltage from step 11 greater than the specified
value?

5.2 volts DC

Go to Step 15

Go to Step 16

Inspect for a short to power in circuit 437.
Did you find a problem?

—

Go to Step 21

Go to Step 20

Inspect circuit 437 for continuity or short to ground.
Refer to Electrical Diagnosis, Section 8.
Did you find a problem?

—

Go to Step 21

Go to Step 19

Replace the OSS Sensor. Refer to 4L80-E On-Vehicle
Service Speed Sensor Replacement.
Is the replacement complete?

—

Go to Step 21

—

Replace the VSS Buffer Module.
Is the replacement complete?

—

Go to Step 21

—

Inspect the PCM terminals and connector for proper ten-
sion or corrosion.
Did you find a problem?

—

Go to Step 21

Go to Step 20

Replace the PCM. Refer to PCM Replacement/Pro-
gramming

, Section 6.

Is the replacement complete?

—

Go to Step 19

—

DTC P0723 Output Speed Sensor Intermittent (Cont’d)

Step

Action

Value

Yes

____________________________________________

Transmission/Transfer Case 5-77

05745159

In order to verify your repair, perform the fol-
lowing procedure:

Select DTC.

Select Clear Info.

Operate the vehicle under the following conditions:

• Drive the vehicle in D3.

• The PCM must see a Transmission OSS greater

than 200 RPM and no change greater than 1000
RPM for 1 second.

Select Specific DTC. Enter DTC P0723.

Has the test run and passed?

—

System OK

Begin the

Diagnosis

again. Go to

Step 1

DTC P0723 Output Speed Sensor Intermittent (Cont’d)

Step

Action

Value

Yes

5-78

Transmission/Transfer Case

_____________________________________________

DTC P0724 Brake Switch Circuit High Input

Circuit Description

The brake switch indicates brake pedal position. The normally-
closed brake switch supplies a B+ signal on circuit 810 to the
PCM. The signal voltage circuit is opened when the brakes are
applied. The PCM uses this signal to deenergize the converter
clutch solenoid when the brakes are applied.

This DTC detects a closed brake switch during decelerations.

Conditions For Setting DTC

• No DTC P0722, P0723.

• The PCM detects a closed brake switch/circuit (12

volts) for 2 seconds during decelerations and the follow-
ing events occur seven consecutive times: vehicle speed
is greater than 32 km/h (20 mph) for 6 seconds; then ve-
hicle speed is between 8 and 32 km/h (5 and 20 mph) for
4 seconds; then vehicle speed is less than 8 km/h (5
mph).

• All conditions exist with 7 occurrences.

Action Taken When The DTC Sets

• PCM disregards the brake switch state if TPS is greater

than 12% and vehicle speed is greater than 45 mph.

• The PCM will NOT illuminate the warning lamp.

Conditions For Clearing The DTC

• The DTC can be cleared using a scan tool. The DTC

will be cleared when the vehicle has achieved 40 warm-
up cycles without a failure reported.

• The PCM will cancel the DTC default actions when the

fault no longer exists and the ignition is cycled “off”
long enough to power down the PCM.

Diagnostic Aids

• Inspect the wiring for poor electrical connections at the

PCM and brake switch. Look for bent, backed out, de-
formed or damaged terminals. Check for weak terminal
tension as well. Also check for a chafed wire that could
short to bare metal or other wiring. Inspect for a broken
wire inside the insulation.

• When diagnosing for a possible intermittent short or

open condition, move the wiring harness while observ-
ing test equipment for a change.

• Check customer driving habits and/or unusual traffic

conditions (i.e. stop and go, expressway).

• Check brake switch for proper mounting and adjust-

ment.

• If any engine DTCs or TPS codes are present diagnose

and clear these DTCs first. Then check to see if the
transmission DTCs have reset.

FUSE 4D

15 AMP

INTERIOR

FUSE 6B

5 AMP

INTERIOR

HOT AT
ALL TIMES

HOT IN RUN
AND START

STOP LAMP
SWITCH

TCC CRUISE
BRAKE SWITCH

TO
STOP
LAMPS

10 OR

291 PK

22 RD

810 PP

STOP

LAMP

SIGNAL

TCC/ CRUISE

BRAKE SIGNAL

FUSE 2C

10 AMP

INTERIOR

HOT IN RUN
AND START

C1-1

A/C COMPRESSOR

ENABLE

RELAY CONTROL

A/C
COMPRESSOR
CLUTCH

DIODE

C5-8

400 LG

A/C COMPRESSOR

CLUTCH RELAY

EXTERIOR

FUSE

BOX

440 RD

59 BK

348 BR

C28-D5

HVAC

CONTROL

MODULE

C6-J8

347 YL

A/C

REQUEST

SIGNAL

TEMPERATURE

CUTOUT

SWITCH

HVAC

UNIT

C1-39

C4-2

198 TN

C4-5

438 OR

439 YL

C27-C2

A/C

REQUEST

SIGNAL

COMPRESSOR

HIGH

PRESSURE

CUTOUT

SWITCH

AMBIENT
TEMP
CUTOUT
SWITCH

LOW
PRESSURE
CUTOUT
SWITCH

9-S12-054

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