A Class 2 serial data communications system is used on this vehicle in order to allow various modules to communicate and share information with each other. Each bit of information has one of two lengths: long or short. This allows for the reduction of the vehicle wiring, and for the transmission and reception of multiple signals over a single wire. The messages carried on the Class 2 serial data stream are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with the higher priority will continue. The message with the lower priority message will wait.

All modules on the Class2 serial data line send out a periodic identifier message. The PCM is listening for the identifier messages from the EBCM and the BFC as well as an echo of the PCM identifier message. If a module cannot respond to the PCM, a DTC is stored.

The PCM has lost communication with the Body Function Controller (BFC) after the PCM received a Theft Passed message from the BFC.

Attempting to start the vehicle by bypassing the Passlock ll system or by substituting parts without performing the password learn procedure may set a DTC P1631 and a P1632.

If no password is received, a DTC P1610 and P1632 may be set.

An intermittent may be caused by the following conditions:

Thoroughly check any suspected circuitry for the following items:

The number(s) below refer(s) to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the fault occurred. The scan tool stores this data for later reference.

2. A scan tool that cannot display the PCM data indicates that a short exists on the serial data circuit.

4. Because of the internal link of the serial data circuits within the PCM, it is necessary to disconnect the PCM electrical connector in order to determine which serial data circuit or the module that the short is in.

6. Reprogram the replacement PCM and perform the crankshaft position system variation learning procedure. Refer to the latest Techline procedures for PCM reprogramming and Powertrain Control Module (PCM) for the crankshaft position variation learning procedure.

7. If the serial data circuit to the Body Function Controller (BFC) was not open, this indicates that the serial communication loss to the PCM lies within the BFC. Refer to Body Function Controller portion of the service manual for Passlock diagnosis.

8. If the serial data loss occurred after a good theft password has been received, the PCM will allow the vehicle to start on following attempts. After making the necessary repairs to the vehicle, reprogram the replacement PCM and complete the password learn procedure and the crankshaft position system variation learning procedures in order to allow the theft system to operate properly. Refer to the Powertrain Control Module (PCM) portion of the service manual for the reprogramming procedures.

9. If no malfunctions are present at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.