Circuit Description
The powertrain control module (PCM) uses a knock sensor (KS) in order to detect engine detonation (spark knock). The knock sensor produces an AC signal at all engine speeds and loads. The PCM makes adjustments to the spark timing based on the amplitude and frequency of the KS signal.
The PCM uses the knock sensor to calculate the amount of normal engine noise (a noise channel) for a wide range of engine speeds and loads. The PCM compares the actual knock sensor signal to the learned noise channel. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system, this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | The engine speed is more than 3,000 RPM. |
| • | The system voltage is greater than 11 volts. |
Conditions for Setting the DTC
The PCM detects a malfunction in the integrated KS diagnostic circuitry that will not allow proper diagnosis of the KS system.
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. |
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 |
Does the scan tool indicate that this DTC passed? | Go to Intermittent Conditions | Go to Step 3 |
3 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | Go to Step 4 | -- |
4 |
Does the scan tool indicate that this DTC passed? | Go to Step 5 | Go to Step 2 |
5 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |
