Hummer H1 (2002+). Instruction - page 67

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Transmission/Transfer Case 5-67

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05745159

DTC P0719 Brake Switch Circuit - Low Input,
Stuck “ON”

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 an open brake switch during acceleration.

Conditions For Setting The DTC

• No DTC P0502.

• The PCM detects an open brake switch/circuit (0 volts)

for 15 minutes without going off for 2 seconds, and the
following events occur seven consecutive times: vehicle
speed is less than 8 km/h (5 mph); then vehicle speed is
between 8 and 32 km/h (5 and 20 mph) for 4 seconds;
then vehicle speed is greater than 32 km/h (20 mph) for
6 seconds.

Action Taken When The DTC Sets

• The PCM will NOT illuminate the warning lamp.

• PCM will disregard the brake switch state if TP is more

than 12% and vehicle speed is greater than 40 mph.

Conditions For Clearing DTC

• The PCM will turn off the warning lamp after three con-

secutive ignition cycles without a failure reported.

• The DTC can be cleared from PCM memory by using a

scan tool. It 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.

FUSE 2D
20 AMP
INTERIOR

FUSE 3A
20 AMP
EXTERIOR

FUSE 4D
15 AMP
INTERIOR

FUSE 6B
5 AMP
INTERIOR

10 OR

291 PK

A

D

BRAKE
LAMP

TCC/

CRUISE

B

C

31

40

C1-

TO BRAKE

LAMP

C28-C13

C28-D13

C28-C12 C28-C11

C29-B10

C29-B9

TCC / CRUISE

BRAKE SWITCH

BRAKE LIGHT

SWITCH SIGNAL

IGNITION

VOLTAGE

BATTERY

POSITIVE

537 OR

POWERTRAIN

CONTROL

MODULE (PCM)

239 PK

9-S12-069

5-68

Transmission/Transfer Case

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Diagnostic Aids

• Inspect the wiring for poor electrical connections at the

PCM and brake switch. Look for damaged terminals,
check for weak terminal tension, inspect for broken
wire.

• When diagnosing for a possible intermittent short or

open condition, move or massage the wiring harness
while observing test equipment for a change.

• Check customer driving habits and/or unusual driving

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

• Check brake switch for proper mounting and adjustment.

• Check for most current calibration I.D. and/or latest bul-

letins.

• If any engine DTCs or TPS codes are present diagnose

and clear these first. Then check to see if the transmis-
sion DTCs have reset.

DTC P0719 Brake Switch Circuit - Low Input

Step

Action

Value

Yes

No

1

1.

Connect scan tool.

2.

Turn the ignition switch “on.”

3.

Record “Freeze Frame” and “Failure Records.'

4.

Select “Brake Switch” on scan tool.

5.

Disconnect brake switch connector from brake
switch.

6.

Install a fused jumper from terminal “C” to terminal
“D” of brake switch connector.

Did brake switch status change from “Open” to
”Closed?'

Go to Step 5

Go to Step 3

2

Remove and inspect brake fuse for an open.
Was the fuse open?

Go to Step 4

Go to Step 6

3

Inspect switch wires for a short to ground.
Was a problem found and corrected?

Go to Step 8

4

Replace the brake switch.

Go to Step 8

5

Inspect switch-to-PCM circuit for open.
Is the repair complete?

Go to Step 8

Go to Step 7

6

Replace PCM.

Go to Step 8

7

1.

After repair is complete, use scan tool to select
“DTC,” then “Clear Info” function.

2.

Select “Specific DTC” and enter DTC “P0719.”

3.

Ensure the following conditions are met:

• Engine running. Select Brake Switch” on scan

tool. Depress the brake to ensure the states
change with the pedal at rest and depressed.

Has the last test failed?

Begin diagno-
sis again, Go to
Step 1

Repair veri-
fied, exit DTC
table.

3-1-01

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Transmission/Transfer Case 5-69

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05745159

DTC P0722 Output Speed Sensor Low Input

Circuit Description

The speed sensor circuit consists of a magnetic induction type
sensor, which is the Output Shaft Speed (OSS) Sensor, a Vehi-
cle Speed Sensor (VSS) Buffer Module, and wiring. Gear teeth
pressed onto the output shaft carrier assembly induce an alter-
nating voltage into the sensor. This signal transmits to the VSS
Buffer Module. The VSS Buffer Module compensates for vari-
ous final drive ratios. The VSS Buffer Module also converts
the AC OSS Sensor signal into a 40 pulse per revolution (PPR)
DC 5 volt square wave form signal on circuit 437 to indicate
transmission output speed.

When the Powertrain Control Module (PCM) detects a low
output speed when the vehicle has a high engine speed in a
drive gear range, then DTC P0722 sets. DTC P0722 is a type B
DTC.

Conditions for Setting the DTC

• No TFP Val. Position Sw. DTC P1810.

• The APP Angle is greater than 12%.

• The engine torque must be 80-450 lb ft. (100-565 N•m).

• The engine speed must be 2000-3800 RPM.

• The A/T ISS Sensor speed is greater than 2000 RPM.

• The transmission is not in Park or Neutral.

• The engine vacuum is 0-105 kPa.

• The OSS Sensor speed is less than 200 RPM for at least

3 seconds.

Action Taken When the DTC Sets

• The PCM Defaults to maximum line pressure.

• The PCM freezes shift adapts.

• The PCM defaults to the calculated output speed value

using the Input Shaft Speed sensor values.

FUSE

3A

20A

EXTERIOR

HOT IN
RUN AND START

TWISTED

PAIR

A/T OUTPUT
SPEED SENSOR
SIGNAL (VSS)

BUFFERED

VSS

SIGNAL

POWERTRAIN

CONTROL

MODULE

(PCM)

VEHICLE

SPEED

SENSOR

(VSS)

A

B

A

B

13

7

C33

676 PP

679 LG

VEHICLE SPEED
SENSOR SIGNAL

IGNITION

POSITIVE
VOLTAGE

9

8

G2

570 BK

239 PK

C29-A3

C29-A6

565 BR

223 DB

14

4

VSS

SIGNAL

OUTPUT

BUFFERED

SPEED

SENSOR

SIGNAL

C3-P9

353 YL

11

C1-18

SPEEDO

VEHICLE
SPEED
SENSOR
BUFFER
(DRAC)

GROUND

SPEEDO

SIGNAL

9-S12-068

5-70

Transmission/Transfer Case

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Conditions for Clearing the DTC

1.

The PCM turns OFF the MIL after three consecutive igni-
tion cycles without a failure reported.

2.

A scan tool can clear the DTC from the PCM history. The
PCM clears the DTC from the PCM history if the vehicle
completes 40 warm-up cycles without a failure reported.

3.

The PCM cancels the DTC default actions when the fault
no longer exists and the ignition is OFF long enough in
order to power down the PCM.

Diagnostic Aids

Inspect the wiring for poor electrical connections at the
PCM. Inspect the wiring for poor electrical connections at
the transmission 20-way connector. Look for the following
problems:

• 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, mas-
sage the wiring harness while watching the test equipment
for a change. It may be necessary to drive the vehicle.

Inspect the Speed Sensor wiring for contact with sharp
metal edges.

Test Description

The numbers below refer to the step numbers on the diagnostic
table.

2. This step verifies the fault condition.

3. This step tests OSS Sensor integrity.

9. This step verifies power and ground to the VSS Buffer

Module.

15.This step verifies the PCM input controlled by the

Speed Buffer.

DTC P0722 Output Speed Sensor Low Input

Step

Action

Value

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) Sys-
tem Check Performed

Go to Step 2

Go to Power-

train OBD

System Check

2

1.

Install the scan tool (Tech 1)

2.

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

Important

: Before clearing the DTCs, 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
and DTCs.

4.

Raise the drive wheels and support the axle assem-
bly.

5.

Start the engine and place the transmission in Drive
3 range.

6.

Gradually increase the wheel speed.

Does the Transmission OSS increase with the drive
wheel speed?

Cannot verify

faulty. Exit

DTC table and

go to Diagnos-

tic Aids

Go to Step 3

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