GM Service Manual Online
For 1990-2009 cars only

Object Number: 190383  Size: SF
Handling ESD Sensitive Parts Notice
Engine Controls Components
Ignition System Controls
OBD II Symbol Description Notice

Circuit Description

The control module uses the knock sensors (KS) in order to detect engine detonation. Ignition control (IC) spark timing is retarded based on the KS signal input when spark knock is detected.

The control module monitors normal engine background noise during warm engine operation. It stores these noise values for comparison to the current knock sensor signal in order to help discriminate between normal engine noise and knock. If the amount of noise is below the minimum stored noise value, this diagnostic trouble code (DTC) will set.

Conditions for Running the DTC

    • No active ECT sensor DTCs
    • No active TP sensor DTCs
    • The timing retard is 0 degrees or less.
    • System voltage is between 10-17.1 volts
    • The ECT is more than 60°C (140°F)
    • The engine run time is more than 2 minutes
    • The knock sensor noise is less than 3 counts
    • The engine speed is between 2,000-3,000 RPM
    • The throttle position is more than 6%

Conditions for Setting the DTC

The difference between the actual noise value and the learned minimum noise value is less than 50 counts or more than 200 counts

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
    • The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.

Conditions for Clearing the MIL or DTC

    • The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
    • A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
    • Use a scan tool in order to clear the DTCs.

Diagnostic Aids

Check for the following conditions:

    • A misrouted harness. Inspect the knock sensor harness in order to ensure that it is not routed too close to high voltage wires such as spark plug leads.
    • An improperly torqued knock sensor-- Refer to

Notice: Replacement components must be the correct part number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

in Cautions and Notices. Torque the Knock Sensor to 19 N·m (14 lbs ft).

Review the Fail Records vehicle mileage since the diagnostic test last failed in order to determine how often the conditions occur that caused the DTC to set . This may assist in diagnosing the condition.

An intermittent may be caused by any of the following conditions:

    • A poor connection
    • Rubbed through wire insulation
    • A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Ensures that the condition is present.

  2. Ensures that the knock sensor is capable of detecting detonation. Striking the lift bracket with a non-metallic object should produce a signal that the knock sensor can detect.

  3. Ensures that the 5 volt reference is near the specified value without being more than 5.2 volts.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure records for reference. This data will be lost when you use the Clear DTC Information function.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Operate the engine within the Conditions for Running the DTC in the supporting text.
  2. Monitor the Specific DTC info for DTC P0327 until the DTC P0327 test runs with a scan tool.
  3. Observe the test results.

Does the scan tool indicate the DTC P0327 Failed This Ignition?

--

Go to Step 4

Go to Step 3

3

  1. Turn ON the Ignition leaving the engine OFF.
  2. Review the scan tool Failure Records data.
  3. Record the scan tool Failure Records data for DTC P0327.
  4. Operate the vehicle within the Failure Records conditions.
  5. Monitor the Specific DTC info for the DTC P0327 until the DTC P0327 test runs with a scan tool.
  6. Observe the test results.

Does the scan tool indicate the DTC P0327 Failed This Ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

  1. Disconnect the knock sensor harness connector.
  2. Measure the resistance of the knock sensor by connecting a J 39200 DMM between the knock sensor terminal and the engine block.

Is the resistance of the knock sensor near the specified value?

100K ohms

Go to Step 5

Go to Step 14

5

  1. Monitor the frequency between the KS terminal and the engine ground with a J 39200 DMM set to the hz scale.
  2. Observe the signal indicated on the J 39200 DMM while tapping on the engine lift bracket with a non-metallic object.

Is any signal indicated on the DMM while tapping on the engine lift bracket?

--

Go to Step 6

Go to Step 14

6

  1. Check the KS signal circuit for a poor terminal connection at the knock sensor.
  2. Repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find a problem?

--

Go to Step 20

Go to Step 7

7

  1. Turn ON the ignition, leaving the engine OFF.
  2. Measure the voltage on the KS signal circuit at the knock sensor harness connector with a J 39200 DMM connected to a ground.

Is the voltage near the specified value?

5 V

Go to Step 15

Go to Step 8

8

With the J 39200 DMM still connected to the knock sensor harness connector, check the voltage.

Is the voltage more than the specified value?

5.2 V

Go to Step 9

Go to Step 10

9

  1. Turn OFF the ignition.
  2. Disconnect the VCM C2 connector.
  3. Probe the KS signal circuit at the KS harness connector with a J 39200 DMM connected to a ground.

Is the voltage more than the specified value?

0 V

Go to Step 13

Go to Step 19

10

  1. Turn OFF the ignition.
  2. Check the KS signal circuit between the VCM and the KS harness connector for an open or high resistance.
  3. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Step 20

Go to Step 11

11

Probe the KS harness connector with a J 35616-200 unpowered test lamp connected to B+.

Is the test lamp ON?

--

Go to Step 12

Go to Step 15

12

Repair the short to ground in the knock sensor signal circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 20

--

13

Repair the short to voltage in the KS signal circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 20

--

14

Replace the Knock Sensor Module. Refer to VCM Replacement/Programming .

Is the action complete?

--

Go to Step 20

--

15

  1. Turn OFF the ignition.
  2. Disconnect the VCM C2 connector.
  3. Check the KS signal circuit for a poor connection at the VCM.
  4. Repair the connection as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find a problem?

--

Go to Step 20

Go to Step 16

16

Check the knock sensor module for not being fully seated or for incorrect installation. Refer to VCM Replacement/Programming .

Did you find a problem?

--

Go to Step 20

Go to Step 17

17

Replace the knock sensor module. Refer to VCM Replacement/Programming .

Is the action complete?

--

Go to Step 18

--

18

  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 21

Go to Step 19

19

  1. Replace the VCM.
  2. Program the new VCM. Refer to VCM Replacement/Programming .
  3. Perform the Passlock Reprogramming Procedure. Refer to PASSLOCK Reprogramming Seed and Key in Theft Deterrent.
  4. Perform the CKP System Variation Learning Procedure. Refer to Crankshaft Position System Variation Learn .

Is the action complete?

--

Go to Step 20

--

20

  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 21

Go to Step 2

21

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the applicable DTC table

System OK