NOTE: Before replacing the Powertrain Control Module (PCM), be certain to check the related component/
circuit integrity for failures not detected due to a double fault in the circuit. Most PCM driver/control circuit
failures are caused by internal component failures (i.e. relays and solenoids) and shorted circuits (i.e. pull-
ups, drivers, and switched circuits). These failures are difficult to detect when a double fault has occurred
and only one DTC has been set.

When a Powertrain Control Module (PCM) and the Sentry Key REmote Entry Module (SKREEM) on vehicles
equipped with the Sentry Key Immobilizer System (SKIS) are replaced at the same time, perform the following steps
in order:

1. Program the new PCM.

ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

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2. Program the new SKREEM (also sometimes referred to as the Wireless Control Module or WCM).

3. Replace all ignition keys and program them into the new SKREEM/WCM.

PROGRAMMING THE PCM/SKREEM

The SKIS Secret Key is an ID code that is unique to each SKREEM/WCM. This code is programmed and stored in
the SKREEM/WCM, the PCM, and each ignition key transponder chip. When the PCM or SKREEM/WCM is
replaced, it is necessary to program the Secret Key into the new module using a diagnostic scan tool. Follow the
programming steps outlined in the diagnostic scan tool for “PCM Replaced” or “WCM Replaced” under “Miscella-
neous Functions” for the “WCM/Wireless Control Module” menu item as appropriate.

NOTE: Be certain to enter the correct country code for the SKREEM/WCM. If the incorrect country code is
programmed into the SKREEM, it cannot be changed and the SKREEM must be replaced.

NOTE: If the PCM and the SKREEM/WCM are replaced at the same time, all vehicle ignition keys will need
to be replaced and new keys programmed into the new SKREEM/WCM.

NOTE: Programming the PCM or SKREEM is done using a diagnostic scan tool and a PIN to enter secure
access mode. If three attempts are made to enter secure access mode using an incorrect PIN, secure
access mode will be locked out for one hour. To exit this lockout mode, turn the ignition to the RUN posi-
tion for one hour then enter the correct PIN. (Ensure all accessories are turned OFF. Also monitor the bat-
tery state and connect a battery charger if necessary).

PROGRAMMING IGNITION KEYS TO THE SKREEM

Each ignition key transponder also has a unique ID code that is assigned at the time the key is manufactured.
When a key is programmed into the SKREEM/WCM, the transponder ID code is learned by the module and the
transponder acquires the unique Secret Key ID code from the SKREEM/WCM. To program ignition keys into the
SKREEM/WCM, follow the programming steps outlined in the diagnostic scan tool for “Program Ignition Keys or Key
FOBs” under “Miscellaneous Functions” for the “WCM/Wireless Control Module” menu item.

NOTE: A maximum of eight keys can be learned to each SKREEM. Once a key is learned to a SKREEM, that
key has acquired the Secret Key for that SKREEM and cannot be transferred to any other SKREEM or vehi-
cle.

If ignition key programming is unsuccessful, the scan tool will display one of the following error messages:

•

Programming Not Attempted - The scan tool attempts to read the programmed key status and there are no
keys programmed into SKREEM memory.

•

Programming Key Failed (Possible Used Key From Wrong Vehicle) - SKREEM is unable to program an
ignition key transponder due to one of the following:

− The ignition key transponder is faulty.
− The ignition key transponder is or has been already programmed to another vehicle.

•

8 Keys Already Learned, Programming Not Done - The SKREEM transponder ID memory is full.

•

Learned Key In Ignition - The ID for the ignition key transponder currently in the ignition lock cylinder is
already programmed into SKREEM memory.

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ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

MODULE-ANTI-LOCK BRAKES

DESCRIPTION

The Antilock Brake Module (ABM) is a microprocessor which handles testing, monitoring and controlling the ABS
brake system operation.

The ABM is mounted on the top of the hydraulic control unit (HCU). The ABM operates the ABS system and is
separate from other vehicle electrical circuits. ABM voltage source is through CKT A111 (fused B+).

NOTE: If the ABM needs to be replaced, the rear axle type and tire revolutions per mile must be programed
into the new ABM. For axle type refer to Group 3 Differential and Driveline. For tire revolutions per mile,
(Refer to 22 - TIRES/WHEELS/TIRES - SPECIFICATIONS) . To program the ABM refer to the Appropriate
Diagnostic Service Information.

OPERATION

SYSTEM SELF-TEST

When the ignition switch is turned-on the microprocessor is tested. If an error occurs during the test, a DTC will be
set into the memory. However it is possible the DTC will not be stored in memory if the error has occurred in the
module were the DTC’s are stored.

The ABM contains a self check program that illuminates the ABS warning light when a system fault is detected.
Faults are stored in memory and are accessible with the scan tool.

ABS faults remain in memory until cleared, or until after the vehicle is started approximately 50 times. Stored faults
are not erased if the battery is disconnected.

ABM INPUTS

The ABM continuously monitors the speed of the vehicle by monitoring signals generated by the wheel speed sen-
sors. The ABM determines a wheel locking tendency when it recognizes the axle is decelerating too rapidly. The
ABM monitors the following inputs to determine when a wheel locking tendency may exists:

•

Wheel Speed Sensors

•

Brake Lamp Switch

•

Brake Fluid Level Sensor

•

G-Sensor (4X4 TCS)

•

4WD Switch (If equipped)

ABM OUTPUTS

The ABM requests the following outputs for antilock braking and brake warning information from the CCN via CAN
C Bus:

•

ABS Warning Lamp

•

Brake Warning Lamp

REMOVAL

NOTE: If the ABM needs to be replaced, the rear axle type and tire revolutions per mile must be programed
into the new ABM. For axle type refer to Group 3 Differential and Driveline. For tire revolutions per mile,
(Refer to 22 - TIRES/WHEELS/TIRES - SPECIFICATIONS). To program the ABM refer to the Appropriate Diag-
nostic Service Information.

ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

8E - 191

1. Remove the HCU from the vehicle (Refer to 5 -

BRAKES/HYDRAULIC/MECHANICAL/HCU
(HYDRAULIC CONTROL UNIT) - REMOVAL).

2. Remove the module mounting screws (1).

3. Disconnect the pump electrical connector (3) from

the HCU (2).

4. Remove the module (1) from the HCU (2).

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ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

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