GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Seville - RHD 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 DTC P0327

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 determine the amount of normal engine noise (noise channel) for a wide range of engine speeds and loads. The PCM compares the actual knock sensor signal to the learned noise channel. The PCM uses the noise channel to diagnose the knock sensor and related wiring. If the PCM detects a loss of the noise channel, 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 more than 11 volts.

Conditions for Setting the DTC

The PCM detects a KS signal less than 0.4 volt.

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.

Diagnostic Aids

If the condition is intermittent, refer to Intermittent Conditions .

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Start the engine.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.
  3. With the scan tool, monitor the Specific DTC Information for DTC P0327 until the test runs.

Does the scan tool indicate that DTC P0327 failed last test?

Go to Step 4

Go to Step 3

3
  1. Review and record the scan tool Freeze Frame/Failure Records Data.
  2. Operate the vehicle within the Freeze Frame/Failure Records conditions.
  3. With the scan tool, monitor the Specific DTC Information for this DTC until the test runs.

Does the scan tool indicate that this DTC passed?

Go to Intermittent Conditions

Go to Step 4

4
  1. Turn OFF the ignition and wait 30 seconds.
  2. Disconnect the PCM connector.
  3. Connect a DMM between the KS signal circuit and the KS low reference circuit.
  4. Set the DMM to the 400 mV AC hertz scale and wait for the DMM to stabilize at 0 Hz. Refer to Measuring Frequency in Wiring Systems.
  5. Observe the DMM while tapping on the engine block with a non-metallic object.

Does the DMM display a fluctuating frequency while tapping on the block?

Go to Step 5

Go to Step 6

5
  1. Turn ON the ignition, with the engine OFF.
  2. With the scan tool, save the Freeze Frame/Failure Records data stored when the DTC set.
  3. Turn OFF the ignition.
  4. Reconnect the knock sensor/starter solenoid harness connector.
  5. Disconnect PCM connector.
  6. With the DMM, measure the frequency between the KS signal and the KS low reference circuits while tapping on the block with a non-metallic object.

Does the DMM display a fluctuating frequency while tapping on block?

Go to Step 8

Go to Step 7

6
  1. Remove intake manifold. Refer to Intake Manifold Replacement in Engine Mechanical 4.6L.
  2. Test for the following conditions:
    3. • A short to low reference in the KS signal circuit between the harness connector and the knock sensor.
    • An open or a short to ground in the KS signal circuit between the harness connector and the knock sensor
    • A signal circuit for a short to voltage
    • An open KS low reference circuit between the harness connector and the knock sensor
    • Poor connections at the knock sensor--Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  3. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

Locate and repair the following circuit conditions between the harness connector and the PCM.

  1. Poor connections in the knock sensor/starter solenoid harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring System.
  2. An open or a short to ground in the KS signal circuit, PCM side of harness connector
  3. An open KS low reference circuit, PCM side of harness connector--Check for short to voltage.
  4. A short to low reference in the KS signal circuit, PCM side of harness connector

Is the action complete?

Go to Step 11

--

8
  1. Inspect for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If the condition is found, repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

9

Replace the knock sensor. Refer to Knock Sensor Replacement .

Is the action complete?

Go to Step 11

--

10

Replace the PCM. Refer to Powertrain Control Module Replacement .

Is the action complete?

Go to Step 11

--

11
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 12

Go to Step 4

12

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

System OK