Serial Link Ext Failure, PCM Status Fail or Rolling Code Fail

NAME OF CODE
Serial Link External Failure

WHEN MONITORED
At ignition On, after ignition ON during any rolling code handshake that occurs with the PCM due to a SKIM reset or a PCM reset, or during "Secret Key" transfers to the PCM.

SET CONDITION
This condition is set when the SKIM does not receive an expected bus message transmission acknowledgment from the PCM after 3 transmit attempts.

THEORY OF OPERATION
The SKIM monitors the data bus for PCM bus message acknowledgments.

POSSIBLE CAUSES
- PCI bus wire in the wiring harness is open
- PCI bus wire in the wiring harness is shorted to ground
- PCI bus wire in the wiring harness is shorted to battery voltage
- Defective Sentry Key Immobilizer Module
- Defective Powertrain Control Module





NAME OF CODE
PCM Status Failure

WHEN MONITORED
This condition is monitored at ignition ON and continuously during an ignition on cycle.

SET CONDITION
This condition exists when a PCM STATUS bus message was not received from the PCM.

NOTE: Failure maturity time is 20 seconds.

THEORY OF OPERATION
The PCM transmits a STATUS message to the SKIM on a repetitive basis. This message informs the SKIM whether the PCM thinks it has received a "valid key" or an "invalid key" message from the SKIM.

POSSIBLE CAUSES
- PCI bus wire in the wiring harness is open
- PCI bus wire in the wiring harness is shorted to ground
- PCI bus wire in the wiring harness is shorted to battery voltage
- Defective Sentry Key Immobilizer Module
- Defective Powertrain Control Module





NAME OF CODE
Rolling Code Failure

WHEN MONITORED
At ignition ON, after ignition ON during any rolling code handshake that occurs with the PCM due to a SKIM or PCM reset.

SET CONDITION
This condition exists when a PCM STATUS message is not received by the SKIM within 3.5 seconds of transmitting what the SKIM believes to be a "key code" message to the PCM. The "key code" sent by the SKIM may or may not be "valid" in this case.

THEORY OF OPERATION
The PCM transmits a PCM STATUS message to the SKIM on a repetitive basis. This message informs the SKIM whether the PCM thinks it has received a "valid key" or an invalid key" message from the SKIM.

POSSIBLE CAUSES
- PCI bus wire in the wiring harness is open
- PCI bus wire in the wiring harness is shorted to ground
- PCI bus wire in the wiring harness is shorted to battery voltage
- Defective Sentry Key Immobilizer Module
- Defective Powertrain Control Module