Circuit Description
The knock sensor is a piezoelectric device that produces an output voltage based on mechanical engine vibration. the powertrain control module (PCM) will retard the electronic spark timing on the signal being received. The knock sensor producers an AC signal. The amplitude and signal frequency is dependant upon the knock level. Upon diagnosis of the sensor circuit, the PCM will learn a minimum engine noise level at idle and compare it to a noise level at around 2000-3000 RPM. This change does not necessarily mean spark knock is detected but that the sensor is giving the PCM a voltage signal based on the level of noise that it sees. When the PCM monitors the circuit, it will set a DTC if thers is no change in output from the knock sensor between idle and 2000-3000 RPM.
Conditions for Setting the DTC
A DTC P0327 will set if:
There is an open or fault in the knock sensor circuit.
| • | The PCM has learned a minimum noise level at idle for 5.0 seconds and does not detect a change in noise level between 2500-3500 RPM for 5.0 seconds. |
| • | The engine coolant temperature is greater then 65°C (149°F). |
| • | The engine run time is greater than 10 seconds. |
| • | The vehicle is moving to reach 2500-3500 RPM. |
Diagnostic Aids
When attempting to diagnose an intermittent problem, use the scan tool to review the malfunction history diagnostic information. The supplemental data can be used to duplicate a problem.
Intermittents or opens suspected to be at the connector can be detected by using a diagnostic service probe. Voltage can be read on wires without disconnecting any connectors.
| • | The resistance to ground through the knock sensor should be around 100,000 ohms at 21°C (70°F) |
| • | A loose sensor could set DTC P0327. |
Tighten
Tighten the sensor to 15 N·m (133 lb in).
Important: The knock sensor has a different internal resistor and cannot be substituted for previous model years.
