Hummer H2. Manual - part 175

DTC P1631

Circuit Description

The Class 2 Serial Data circuit is used in order to communicate between the powertrain control module (PCM)
and the vehicle theft deterrent body control module (BCM) systems.

When the passlock portion of the VTD system has sensed the proper operation of the ignition switch and lock,
or determined that the switch and lock have not been tampered with, the BCM transmits a password to the
PCM. Fuel delivery is enabled if this password matches the password stored in the modules memory. If a
component in the theft deterrent system has been replaced, the modules need to relearn the password of the new
components. If the relearn procedure was not performed, this diagnostic trouble code (DTC) will set.

If a VTD failure occurs during an ignition cycle that the PCM has enabled fuel, then the BCM will enter a fail-
safe mode: Fail Enable VTD System Failure with Fuel Enabled. The BCM remains in Fail Enable Mode, for the
current and future ignition cycles, until the fault is corrected and a valid password is received, or until battery
power is removed. If the battery is disconnected or the codes are cleared, the vehicle will lose its Fail Enable
status and will not start until the fault is corrected, the ten minute timer expires, and the PCM receives the
correct fuel delivery password.

Conditions for Running the DTC

DTC P1626 is not active.

The powertrain control module (PCM) is not in password learn mode.

The VTD Passlock system is enabled.

The fuel enable decision point has been reached, or the engine is cranking.

Conditions for Setting the DTC

The powertrain control module (PCM) did not receive a valid password before the fuel disable decision point
was reached.

Action Taken When the DTC Sets

The powertrain control module (PCM) stores the DTC in history after the first failure but will not
illuminate the malfunction indicator lamp (MIL).

The PCM records the operating conditions at the time the diagnostic fails. The PCM stores the failure
information in the scan tools Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC

A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles.

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

Go to Step 7

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the start-up coolant
temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle.

Use the scan tool Clear Information function.

Diagnostic Aids

If the powertrain control module (PCM) is replaced, the PCM must re-learn a valid password and
crankshaft variation.

If the body control module (BCM) is replaced, the PCM must re-learn a valid password.

Check for published service bulletins relating to exhibited symptoms or component operation.

If the vehicle does not start, or starts and stalls:

{

Turn OFF the ignition and wait at least 5 seconds before trying to restart.

{

If a fault or tamper has been detected, the BCM will not forward the correct password to the PCM
for a period of ten minutes, even if the condition is corrected during that time period. This may
cause a DTC P1631 to set in the PCM. This timer can be monitored in the Passlock Data parameter
of the scan tool. Once the time has elapsed, the BCM will determine if the condition is still present.

The PCM and BCM parameters can be monitored with a scan tool.

The Passlock state and the auto learn timer can be viewed in the Passlock Data parameter of the scan tool.

Check the following for preventing the Passlock sensor from communicating with the BCM:

{

Passlock sensor

{

Ignition switch assembly

{

Passlock sensor circuitry

{

Bent pins at the small Passlock sensor

If this DTC sets along with a DTC B2960, then the problem was caused by malfunctioning Passlock
components or circuitry, not the PCM.

Inspect all related wiring and connections including the PCM and BCM connections. These may cause an
intermittent malfunction.

An intermittent may be caused by any of the following conditions:

A poor connection

Rubbed through wire insulation

A broken wire inside the insulation

Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for
Intermittent Conditions and Poor Connections in Wiring Systems.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

IMPORTANT: Do not clear DTCs unless directed by a diagnostic procedure. Clearing DTCs

will also clear valuable Freeze Frame and Failure Records data.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

Test Description

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

2: This DTC may set as a result of other Passlock System problems. Diagnose any BCM DTCs prior to
continuing with this diagnostic.

3: A DTC B3031 may set in the body control module (BCM) during the Password Learn Procedure.

DTC P1631

SYMPTOMS - THEFT DETERRENT

Important Preliminary Checks Before Starting

Step

Action

Yes

Schematic Reference:Data Link Connector (DLC) Schematics

Did you perform the Vehicle Theft Deterrent
(VTD) Diagnostic System Check?

Go to

Step 2

Go to Diagnostic System Check -

Theft Deterrent

1. Install a scan tool.

2. Momentarily rotate the ignition switch to

CRANK. Do not start the vehicle.

3. Release the ignition switch to ON.

4. Select the Powertrain control module

display DTCs function on the scan tool.

Does the scan tool display DTC P1631 as a
current DTC?

IMPORTANT:

You must diagnose the Bxxxx codes prior to
diagnosing any Pxxxx code.

Go to

Step 3

Go to Testing for Intermittent

Conditions and Poor Connections

in Wiring Systems

Perform the Passlock Programming procedure.
Refer to Programming Theft Deterrent System
Components .
Did the PCM successfully learn the password?

Go to

Step 4

Go to Diagnostic System Check -

Theft Deterrent

1. Clear the PCM DTCs.

2. Turn OFF the ignition for 30 seconds.

3. Attempt to start the engine.

Does the engine start and operate normally?

IMPORTANT:

Before Clearing DTCs, monitor all DTC status
parameters and note any additional DTCs.

System

Go to Step 2

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

1. Perform the Diagnostic System Check - Theft Deterrent before using the Symptom Tables in order to

verify that all of the following are true:

There are no DTCs set.

The control modules can communicate via the serial data link.

2. Review the vehicle theft deterrent description and operation in order to familiarize yourself with the

system functions. Refer to Vehicle Theft Deterrent (VTD) Description and Operation .

3. Review the content theft deterrent description and operation in order to familiarize yourself with the

system functions. Refer to Content Theft Deterrent (CTD) Description and Operation .

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the Passlock(tm) system. Refer to
Checking Aftermarket Accessories in Wiring Systems.

Inspect the easily accessible or visible system components for obvious damage or conditions which could
cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for
Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

Security Indicator Always On or Flashing

Security Indicator Inoperative

Content Theft Deterrent (CTD) Alarm Mode Inoperative

Content Theft Deterrent (CTD) Does Not Disarm with Key Lock

Horn Inoperative in Content Theft Deterrent (CTD) Alarm Mode

Lights Inoperative in Content Theft Deterrent (CTD) Alarm Mode

The engine Cranks and will not Start, No Security light on. Refer to DTC B2958

CONTENT THEFT DETERRENT (CTD) ALARM MODE INOPERATIVE

Content Theft Deterrent (CTD) Alarm Mode Inoperative

Step

Action

Yes

Schematic Reference:Theft Deterrent System Schematics
Connector End View Reference:Theft Deterrent System Connector End Views
DEFINITION: The CTD system will not ARM or DISARM properly.

Did you perform A Diagnostic System
Check - Theft Deterrent?

Go to Step 2

Go to Diagnostic System
Check - Theft Deterrent

1. Open the driver's window.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Theft Deterrent - Hummer H2

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