Circuit Description
The knock sensors (KS) produce an AC signal when specific frequencies are detected. When the engine operates, the powertrain control module (PCM) learns a minimum and maximum frequency of noise of normal engine operation. The KS system monitors both knock sensors in order to determine if knock is present. If the KS system determines that excess knock is present, the PCM retards the spark timing based on the signals from the KS system. The PCM retards timing until the knock is not present.
Conditions for Running the DTC
| • | The engine is running. |
| • | The engine run time is more than 10 seconds. |
| • | The ignition voltage is more than 10 volts. |
Conditions for Setting the DTC
A malfunction with the KS system or circuits within the PCM are faulty for 15 seconds or more.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 |
Important: If you can hear the engine knock, repair the engine mechanical condition before proceeding with this diagnostic.
Does the DTC fail this ignition? | Go to Step 3 | Go to Intermittent Conditions |
3 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 4 | -- |
4 |
Does the scan tool indicate that this test ran and passed? | Go to Step 5 | Go to Step 2 |
5 | Use a scan tool in order to observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |
