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 KS system uses two sensors. The sensors are located underneath the intake manifold. Each KS produces an AC signal that varies 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 receives the KS signal through a signal circuit. The KS ground is supplied by the PCM through a low reference circuit. The PCM uses each KS 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 KS signal to the learned noise channel. When the PCM detects a KS signal that varies outside of the noise channel, the PCM will retard the spark timing until the knock goes away. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0325 Knock Sensor (KS) Circuit
Conditions for Running the DTC
| • | The engine load meets or exceeds a calibrated specification. |
| • | The system voltage is greater than 11 volts. |
| • | DTC P0325 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
The PCM detects a knock sensor voltage greater than 4.8 volts for 40 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. |
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the DTC fail this ignition? | Go to Step 3 | Go to Intermittent Conditions |
3 | Replace the powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. 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? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
