C1275

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Circuit Description
The serial data communications circuit (CKT 800) transmits messages from one electronic control module to another when interface between systems is necessary. The ABS VI/TCS systems depend on information to and from the PCM for proper operation.

Conditions For Setting The DTC
DTC C1275 will set if either of the following conditions occurs:
^ The vehicle speed is greater than 5 km/h (3 mph) and a malfunction exists on the serial data circuit.
^ The PCM has not broadcasted a serial message for at least 10 seconds.

Action Taken When The DTC Sets
^ A malfunction DTC stores.
^ The TCS disables.
^ The amber TCS warning indicator turns on.
^ The ABS remains functional.
^ No action towards the Electronic Brake Control Relay and ABS warning indicator is taken.

Conditions for Clearing The DTC
^ The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTC function is used.
^ 100 drive cycles pass with no DTC detected.

Diagnostic Aids
When DTC 1275 is current (malfunction in CKT 800), no communication can be established with the scan tool. When the malfunction is removed, DTC C1275 will be stored in system memory. Use the enhanced diagnostic function of the Scan Tool to measure the frequency of the malfunction. Refer to the Scan Tool manual or Scan Tool Diagnostics for the procedure.
Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:
^ Rubbed-through wire insulation
^ A broken wire inside the insulation
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal-to-wiring connections
^ Physical damage to the wiring harness

Important: Zero the J39200 test leads before making any resistance measurements.