Knock/Charging Pressure Control On-Board Diagnostics

The Knock/Charging pressure control unit has a self-diagnostic system that is accessed using test relay # 9246. Faults are indicated by blink code displayed by the red LED in the test relay. Fault codes are erased every time the engine is switched off.

Blink Code Extraction
- Road test vehicle sufficiently to cause fault to occur.
- Engine must remain running
- Install test relay in test socket at rear of left fender.
- Raise engine RPM above 1500 RPM.
^ LED remains dark - No fault stored.
^ LED remains lite - Faults stored.
- Allow engine to return to idle.
- LED will output blink code for stored fault.

Blink Code Description and Possible Cause
1 - 2 Supply voltage below 10.2 volts
Check: Alternator, battery, regulator, wiring, and relays
2 - 1 Knock sensor, excessive knock signal
Check: Engine damage, bucket tappets rattle, faulty valve, rod bearing damage, engine knocks
2 - 2 Knock sensor, no or poor signal
Check: Sensor installation torque, plug connection for sensor, wiring from control unit
2 - 3 Knock control (KLR) unit defective
Replace faulty control unit
3 - 1 Charging pressure too low
Check: Wastegate, turbocharger, intercooler for leaks
3 - 2 Charging pressure too high
Check: Wastegate, timing valve for wastegate control, pressure hose to wastegate
3 - 3 Pressure sensor in KLR unit defective
Check: Replace faulty control unit
4 - 1 Throttle potentiometer signal open circuit
Check: Power supply to potentiometer, ground contact, potentiometer tap dirty, wiring for open circuit
4 - 2 Throttle potentiometer signal shorted circuit
Check: Potentiometer signal, wiring for shorted circuit