Circuit Description
The control module uses the knock sensors (KS) in order to detect engine detonation. Ignition control (IC) spark timing is retarded based on the KS signal input when spark knock is detected.
The control module monitors normal engine background noise during warm engine operation. It stores these noise values for comparison to the current knock sensor signal in order to help discriminate between normal engine noise and knock. If the amount of noise is below the minimum stored noise value, this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | No active ECT sensor DTCs |
| • | No active TP sensor DTCs |
| • | The timing retard is 0° or less. |
| • | System voltage is between 10 and 17.1 volts |
| • | The ECT is more than 60°C (140°F). |
| • | The engine run time is more than 2 minutes. |
| • | The knock sensor noise is less than 3 counts. |
| • | The engine speed is between 2,000 and 3,000 RPM. |
| • | The throttle position is more than 6 percent. |
Conditions for Setting the DTC
The difference between the actual noise value and the learned minimum noise value is less than 50 counts or more than 200 counts.
Action Taken When the DTC Sets
| • | The VCM illuminates the MIL during the second consecutive drive cycle in which the diagnostic reports a fail. |
| • | The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Check for the following conditions:
| • | A misrouted harness -- Inspect the knock sensor harness in order to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
| • | Improper knock sensor torque specification |
Tighten
Torque the knock sensor to 19 N·m (14 lbs ft).
Review the Fail Records vehicle mileage since the diagnostic test last failed in order to help determine how often the conditions that caused the DTC to set occur. This may assist in diagnosing the condition.
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Ensures that the condition is present.
-
Ensures that the knock sensor is capable of detecting detonation. Striking the lift bracket with a non-metallic object should produce a signal that the knock sensor should detect.
-
Ensures that the 5 volt reference is near the specified value without being more than 5.2 volts.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the scan tool indicate the DTC P0327 Failed This Ignition? | -- | |||
3 |
Does the scan tool indicate the DTC P0327 Failed This Ignition? | -- | Go to Diagnostic Aids | |
4 |
Is the resistance of each Knock Sensor near the specified value? | 8K ohms | ||
Do both Knock Sensors indicate a signal on the J 39200 DMM while tapping on the engine lift bracket? | -- | |||
6 | Check each of the KS signal circuits for a poor terminal connection at the Knock Sensor. Repair as necessary. Refer to Connector Repairs in Wiring Systems. Did you find a problem? | -- | ||
Is the voltage near the specified value at each sensor? | 5 V | |||
8 | With the J 39200 DMM still connected to the Knock Sensor harness connectors. Is the voltage more than the specified value at either of the sensors? | 5.2 V | ||
9 |
Is the voltage more than the specified value? | 0 V | ||
10 |
Did you find a problem? | -- | ||
11 | Probe the KS harness connectors with a test lamp connected to B+. Is the test lamp ON? | -- | ||
12 | Repair the short to ground in the KS signal circuits. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
13 | Repair the short to voltage in the KS signal circuits. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
14 | Replace the faulty Knock Sensor. Refer to Knock Sensor Replacement . Is action complete? | -- | -- | |
15 |
Did you find a problem? | -- | ||
16 | Check the Knock Sensor module for not being fully seated or for incorrect installation. Refer to VCM Replacement/Programming . Did you find a problem? | -- | ||
17 | Replace the Knock Sensor module. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
18 |
Does the scan tool indicate the diagnostic Passed? | -- | ||
19 |
Important: The replacement VCM must be programmed. Replace the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
20 |
Does the scan tool indicate the diagnostic Passed? | -- | ||
21 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
