Circuit Description
The DTC P0327 Knock Sensor (KS) Circuit Low Frequency diagnostic monitors the activity on the knock sensor circuit. The KS is non-resonant design that is constructed of a piezoelectric element which generates an AC signal, when vibrated. Normal engine operation will cause the KS to generate signals of known frequencies. When engine knock is present, the KS frequency changes. This signals the powertrain control module (PCM) to retard ignition timing. The PCM sends a bias voltage of 5 volts to the KS on the KS Signal High circuit. The PCM expects approximately 2.5 volts back on the KS Signal Low circuit. The KS generated AC signal rides on top of the bias voltage provided by the PCM. For additional information on the operation of the KS refer to Knock Sensor (KS) System Description .
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0327 Knock Sensor (KS) Circuit Low Frequency
Conditions for Running the DTC
| • | The ignition is ON or the engine is running |
| • | DTC P0327 runs continuously once the above condition has been met. |
Conditions for Setting the DTC
The KS signal circuit is less than 0.5 volts for at least 10 seconds.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM stores the conditions that were present when the DTC set as Freeze Frame data. |
| • | The PCM enters the Fail-Safe function and defaults to maximum spark retard values. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | The DTC clears after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear DTC Information function. |
Diagnostic Aids
Inspect for the following conditions:
| • | A loose KS can cause a loss of the KS signal. Check the KS for proper torque. The correct KS sensor torque is 39 N·m (29 lb ft). |
| • | Engine acceleration will be compromised and automatic transmission (AT) downshifts delayed when operating in the Fail-safe mode. |
| • | If a DTC P0327 sets while the engine is idling, inspect for a loose connection at the PCM or KS. |
An intermittent malfunction may be caused by a fault in the KS sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions present when the DTC first set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check-Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step verifies the resistance of the KS.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
2 |
Is the voltage within the specified value? | 4.9-5.1 V | Go to Step 3 | Go to Step 4 |
Is the resistance near the specified value? | 200K ohms at 20°C (68°F) | Go to Diagnostic Aids | Go to Step 5 | |
4 |
Did you find and correct a condition? | -- | Go to Step 7 | Go to Step 6 |
5 | Replace the knock sensor. Refer to Knock Sensor Replacement . Did you complete the replacement? | -- | Go to Step 7 | -- |
6 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 7 | -- |
7 |
Does the DTC run and pass? | -- | Go to Step 8 | Go to Step 2 |
8 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
