P1626
CIRCUIT DESCRIPTION
A Class II serial data communications system is used on this vehicle to allow various modules to communicate and share information with each other. Each bit of information has one of two lengths: long or snort. This allows vehicle wiring to be reduced and the transmission and reception of multiple signals over a single wire. The messages carried on a Class II serial data streams 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. If a module cannot respond to the PCM, a DTC is stored.
CONDITIONS FOR SETTING THE DTC
The PCM cannot communicate with the theft deterrent system.
ACTION TAKEN WHEN THE DTC SETS
^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure
Records buffers.
^ A history DTC is stored.
CONDITIONS FOR CLEARING THE MIL/DTC
^ A history DTC will clear after 40 consecutive warm up cycles without a fault.
^ DTCs can be cleared by using a scan tool.
DIAGNOSTIC AIDS
Attempting to start the vehicle by bypassing the theft deterrent system or substituting parts without performing the password learn procedure may set a DTC P1631.
If no password is received a DTC P1610, P1626 and P1631 may be set.
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly checked for the following items:
^ Backed out terminals or improper mating.
^ Broken locks.
^ Improperly formed or damaged terminals.
^ Poor terminal to wiring connections.
^ Physical damage to the wiring harness.
^ Corrosion.
If the Body Function Controller (BFC) is replaced the PCM must be reflashed to allow the new password to be learned. The ignition must be turned oft for at least 30 seconds then on for the PCM to learn the new BFC password.
TEST DESCRIPTION
Number(s) below refer to the step number(s) on the Diagnostic Table:
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. A scan tool that cannot display PCM data indicates that a short exists on the serial data circuit.
6. The replacement PCM must be reprogrammed and the crankshaft position system variation procedure must be performed.
If the serial data loss occurred after a good theft password has been received, the PCM must be reprogrammed and the password learn and the crankshaft position variation learn procedures must be completed to allow the theft system to operate properly. Refer to PCM Replacement/Programming, Crankshaft Position (CKP) System Variation Learn Procedure and Password Learn Procedure for reprogramming procedures.
7. If the serial data circuit to the Body Function Controller (BFC) was not open, then the serial communication loss to the PCM lies within the BFC. Refer to Body Function Controller for Passlock diagnosis.
9. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.