Circuit Description
The knock sensor (KS) system enables the powertrain control module (PCM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The PCM monitors one KS. The KS is located on the intake side of the engine block. The KS produces an AC voltage signal that varies at all engine speeds and loads. The PCM adjusts the spark timing based on the amplitude and the frequency of the KS signal. The PCM receives the KS signal through a signal circuit. The KS ground is supplied by the PCM through a low reference circuit. The PCM uses the KS signal to calculate the average voltage and then assigns a voltage range value. The PCM should monitor a normal KS signal within the assigned voltage range. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system, this DTC will set.
Conditions for Running the DTC
| • | The engine speed is more than 1,800 RPM. |
| • | The engine load meets or exceeds a calibrated specification. |
| • | The manifold absolute pressure (MAP) is more than 55 kPa. |
Conditions for Setting the DTC
The PCM detects a malfunction in the 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 |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 |
Does the DTC fail this ignition? | Go to Step 3 | Go to Intermittent Conditions |
3 | Replace the powertrain control module (PCM). Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 4 | -- |
4 |
Does the DTC fail this ignition? | Go to Step 2 | Go to Step 5 |
5 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
