Hummer H2. Manual — part 170

DTC B2948

Circuit Description

The Passlock(tm) system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to
rotate or the ignition switch is operated while separated from the ignition lock cylinder case. The body control
module (BCM) provides security system sensor power and low reference for the Passlock(tm) sensor. The BCM
also measures the security system sensor voltage.

When the correct key is used to start the vehicle, a magnet on the lock cylinder passes close to the Passlock(tm)
sensor within the ignition lock cylinder case. The magnet activates the security hall effect sensor in the Passlock

4

Test the Passlock(tm) battery voltage circuit for a short to
ground. Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.
Did you find and correct the condition?

Go to

Step

10

Go to Step 5

5

Inspect for poor connections at the body control module
(BCM). Refer to Testing for Intermittent Conditions and
Poor Connections and Connector Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to

Step

10

Go to Step 7

6

Inspect for poor connections at the Passlock(tm) sensor.
Refer to Testing for Intermittent Conditions and Poor
Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?

Go to

Step

10

Go to Step 8

7

Replace the BCM. Refer to Body Control Module
Replacement in Body Control System.Did you complete
the replacement?

IMPORTANT:

When replacing the BCM refer to Body Control Module
(BCM) Programming/RPO Configuration in Body Control
System.

Go to

Step

10

-

8

Replace the Passlock(tm) sensor. Refer to Ignition Lock
Cylinder Case Replacement in Steering Wheel and
Column.
Did you complete the replacement?

Go to

Step 9

-

9

Perform the Passlock(tm) learn procedure. Refer to
Programming Theft Deterrent System Components .
Did you complete the procedure?

Go to

Step

10

-

10

1. Use the scan tool in order to clear the DTCs.

2. Operate the vehicle within the conditions for running

the DTC as specified in the supporting text.

Does the DTC reset?

Go to

Step 3

System OK

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

(tm) sensor which completes a circuit from the security sensor signal circuit through a resistor to the security
sensor low reference circuit. The resistance value will vary from vehicle to vehicle. The BCM will measure the
voltage on the security sensor signal circuit and compare this voltage to a previously learned voltage. If the
voltage measured is within the valid range, the BCM will send a class 2 message to the powertrain control
module (PCM) to enable vehicle starting. If the voltage measured is not within the valid range, a class 2
message will be sent to the PCM to disable starting of the vehicle.

Conditions for Running the DTC

The ignition switch is cycled to CRANK, released to ON and then cycled to OFF.

Conditions for Setting the DTC

z

The BCM turns the Passlock(tm) sensor power OFF after the ignition switch is turned OFF.

z

If the BCM still senses battery voltage for 1 second after the shut down of voltage, this DTC will set.

Action Taken When the DTC Sets

z

The BCM stores DTC B2948 in memory.

z

The vehicle will start and run.

z

The SECURITY indicator remains illuminated.

Conditions for Clearing the DTC

z

The BCM no longer detects a short to battery in the Passlock sensor power circuit.

z

When a short to battery is no longer present on the Passlock sensor power circuit, the ignition switch must
be cycled from OFF to ON before this DTC can change from a current DTC to a history DTC.

z

A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no
longer present.

Diagnostic Aids

Inspect for a short battery on the Passlock sensor power circuit with the ignition switch OFF.

Test Description

The number below refers to the step number on the diagnostic table.

3: Tests for a short to battery positive on the Passlock battery voltage circuit.

DTC B2948

Step

Action

Yes

No

Schematic Reference:Theft Deterrent System Schematics
Connector End View Reference:Theft Deterrent System Connector End Views

1

Did you perform the Theft Deterrent Diagnostic System

Go to Go to Diagnostic System Check

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

Check?

Step 2

- Theft Deterrent

2

1. Install a scan tool.

2. Turn ON the ignition, with the engine OFF.

3. Select the body control module display DTCs

function on the scan tool.

Does the scan tool display DTC B2948 as a current
DTC?

Go to

Step 3

Go to Testing for Intermittent

Conditions and Poor

Connections in Wiring Systems

3

1. Disconnect the Passlock(tm) sensor connector.

2. Connect a DMM between the Passlock(tm) battery

voltage circuit and a good ground.

3. Set the "MIN MAX" mode to the 1 millisecond

peak and start to record.

4. Turn OFF the ignition.

5. Stop recording and review the recorded "MIN"

value.

Does the voltage measure near zero volts?

IMPORTANT:

The use of a DMM is crucial in this step because
voltage may be measured for 10 milliseconds.

Go to

Step 7

Go to Step 4

4

Test the Passlock battery voltage circuit for a short to
voltage. Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.
Did you find and correct the condition?

Go to

Step

10

Go to Step 5

5

Inspect for poor connections at the BCM. Refer to
Testing for Intermittent Conditions and Poor
Connections and Connector Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to

Step

10

Go to Step 6

6

Inspect for poor connections at the Passlock(tm) sensor.
Refer to Testing for Intermittent Conditions and Poor
Connections in Wiring Systems.
Did you find and correct the condition?

Go to

Step

10

Go to Step 8

7

Replace the body control module. Refer to Body Control
Module Replacement in Body Control System.Did you
complete the replacement?

IMPORTANT:

When replacing the BCM, refer to Body Control
Module (BCM) Programming/RPO Configuration in
Body Control System.

Go to

Step

10

-

Replace the Passlock(tm) sensor. Refer to Ignition Lock

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

DTC B2957

Circuit Description

The Passlock(tm) system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to
rotate or the ignition switch is operated while separated from the ignition lock cylinder case. The body control
module (BCM) provides security system sensor power and low reference for the Passlock(tm) sensor. The BCM
also measures the security system sensor voltage.

When the correct key is used to start the vehicle, a magnet on the lock cylinder passes close to the Passlock(tm)
sensor within the ignition lock cylinder case. The magnet activates the security hall effect sensor in the Passlock
(tm) sensor which completes a circuit from the security sensor signal circuit through a resistor to the security
sensor low reference circuit. The resistance value will vary from vehicle to vehicle. The BCM will measure the
voltage on the security sensor signal circuit and compare this voltage to a previously learned voltage. If the
voltage measured is within the valid range, the BCM will send a class 2 message to the powertrain control
module (PCM) to enable vehicle starting. If the voltage measured is not within the valid range, a class 2
message will be sent to the PCM to disable starting of the vehicle.

Conditions for Setting the DTC

z

The ignition switch is ON.

z

The BCM signal input is less than 0.4 volts for 1 second after turning the ignition switch to the CRANK
position.

Action Taken When the DTC Sets

z

The vehicle will not start if the fault occurs before you start the vehicle. The security indicator will flash
for 10 minutes then turn ON steady.

z

If the vehicle is running when the fault occurs, the BCM will be in the fail enable mode allowing the
vehicle to start and run. The security indicator will be ON.

Conditions for Clearing the DTC

8

Cylinder Case Replacement in Steering Wheel and
Column.
Did you complete the replacement?

Go to

Step 9

-

9

Perform the Passlock(tm) learn procedure. Refer to
Programming Theft Deterrent System Components .
Did you complete the repair?

Go to

Step

10

-

10

1. Use the scan tool in order to clear the DTCs.

2. Operate the vehicle within the conditions for

running the DTC as specified in the supporting
text.

Does the DTC reset?

Go to

Step 3

System OK

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2