DSR21 - Isolate Cause of Noisy PID Value

- If only one PID value is noisy/erratic:
Check associated harness circuit/component for intermittent opens/shorts (refer to Pinpoint Test Step Z1), proper harness routing away from spark plug wires, battery cables, high voltage or high current aftermarket add-on wiring, etc. If all checks are OK, perform the CIRCUIT/COMPONENT NOISE ISOLATION TEST below.

- If multiple PID values are noisy/erratic:
Check for proper harness routing away from spark plug wires, battery cables, high voltage or high current aftermarket add-on wiring, etc. Check any common power or ground circuits. If harness appears OK, perform the CIRCUIT/COMPONENT NOISE ISOLATION TEST below.

CIRCUIT/COMPONENT NOISE ISOLATION TEST

- Engine in same mode (key on, engine off or engine running) as it was when noisy/erratic PID value detected.

- While monitoring PIDs, disconnect fuses/fuse links one at a time.

- If noise is eliminated by pulling a specific fuse, all circuits/components supplied by the fuse need to be checked for excessive noise generation. Disconnect each module/component on the fuse circuit, one at a time, to help isolate the fault.

- Is fault indicated?

YES -- ISOLATE fault and SERVICE as necessary. RE-EVALUATE symptom.

NO -- GO to Pinpoint Test Step Z1 to check for intermittent harness concerns, Z1 - Intermittent Test Procedure

or RETURN to Symptom Flow Chart to continue diagnosis. Testing and Inspection