P0324
P0324-KNOCK CONTROL SYSTEM
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
Knock is the spontaneous auto-ignition of the remaining fuel/air mixture in the engine combustion chamber that occurs after normal combustion has started. It can occur under extreme vehicle operating conditions such as high engine temperature, high MAP, low humidity and heavy loads to the engine. Knock is caused by excessive spark advance for the given engine operating conditions. Severe, continuous knock may be caused by carbon deposits, bad gasoline and/or low octane fuel. Avoiding light audible knock is important for customer satisfaction while preventing excessive knock is important to protect engine components. The output voltage from the knock circuit represents the strength of the engine knock and is read by the engine controller. The knock system output voltage is not zero due to engine background noise, even when knock is not present. When the engine is operated under high load conditions where knock is possible, the knock voltage is tested to decide if it exceeds the knock voltage threshold. Knock has occurred when the knock voltage is at or above this knock threshold. When knock is detected a calibrated short term knock spark retard to be subtracted from the spark advance is calculated. The amount of retarded spark advance is based off a calibrated severity of the knock event. This retarded spark advance is used in the next ignition event to prevent further knock events. If knock continues, an additional amount of short term spark advance retard is added. When knock stops, short term knock spark retard is eliminated, the long term knock spark retard is reduced by a calibrated amount to recover some previously retarded spark advance. This decreases spark retard to improve engine performance.
- When Monitored:
Ignition on, engine not running, coolant temperature greater than -40° C (-40° F) less than 140° C (248° F) and engine oil temperature greater than -40° C (-40° F) less than 200° C (329° F).
- Set Condition:
The Powertrain Control Module detects the that knock sensor capacitance is less than a calibrated value.
Diagnostic Test
1. ACTIVE DTC
1. Diagnose and repair any other active component or circuit DTCs before continuing with this procedure.
2. Turn the ignition on.
3. With the scan tool, select View DTCs. Copy DTC and Freeze Frame information.
4. Operate the vehicle under conditions similar to which the DTC was set.
Are there excessive misfires shown or is the DTC pending at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.
2. (K42) KNOCK SENSOR SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Knock Sensor harness connector.
3. Disconnect the C2 PCM harness connector.
4. Measure the resistance of the (K42) Knock Sensor Signal circuit from the Knock Sensor harness connector to the PCM C2 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 3
No
- Repair the open or resistance in the (K42) Knock Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
3. (K942) KNOCK SENSOR RETURN CIRCUIT OPEN OR HIGH RESISTANCE
1. Measure the resistance of the (K942) Knock Sensor Return circuit from the Knock Sensor harness connector to the PCM C2 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 4
No
- Repair the open or high resistance in the (K942) Knock Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
4. KNOCK SENSOR
1. Turn the ignition off.
2. Verify that there is good pin to terminal contact at the Knock Sensor and the Powertrain Control Module connectors.
3. If no problems were found in the connectors, replace the Knock Sensor. .
4. Connect the Powertrain Control Module (PCM) harness connector.
5. Turn the ignition on.
6. With the scan tool, clear DTCs.
7. Turn the ignition on.
8. With the scan tool, select View DTCs.
Is the DTC Active at this time?
Yes
- Go To 5
No
- Test complete.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors of the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact of the PCM harness connectors.
4. Perform any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.