GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1995 🢒 Camaro 🢒 DTC 🢒 DTC P0326 Knock Sensor Noise Channel High Voltage

Circuit Description

The knock sensors are used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the KS signal being received. The knock sensors produce an AC signal which rides on a 5 volts DC signal supplied by the PCM. The signal amplitude and frequency is dependent upon the amount of knock being experienced.

The PCM determines whether the knock sensors and related wiring are operating properly by monitoring the voltage level on the noise channel. The noise channel allows the PCM to diagnose the KS system by allowing the PCM to learn the amount of normal engine mechanical noise present. Normal engine noise varies depending on engine speed and load. When the PCM determines that an abnormally high noise channel voltage level is being experienced, a DTC P0326 will set.

Conditions for Setting the DTC
    • No active TP sensor, VSS or ECT sensor DTCs are set.
    • The engine has been running for at least 10 seconds.
    • The engine coolant temperature is greater than 65°C (149°F).
    • Throttle angle is greater than 1.5 percent.
    • Engine speed is between 2,500 RPM and 2,900 RPM.
    • Noise channel voltage level is greater than 5 volts is being indicated.

Action Taken When the DTC Sets
    • The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
    • The PCM will store conditions which were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data.
    • The PCM will use a calculated spark retard value to minimize knock during conditions when knock is likely to occur. The calculated value will vary based on engine speed and load.

Conditions for Clearing the MIL/DTC
    • A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using the scan tool Clear Info function.

Diagnostic Aids

Check for the following conditions:

    • Poor connection at the PCM. Inspect knock sensor and PCM connectors for backed out terminals, broken locks, and improperly formed or damaged terminals.
    • Misrouted harness. Inspect the knock sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. Ensures that the fault is present.

    2.

  2. Checks for a false knock signal caused by a faulty knock sensor.

    3.

  3. Ensures that the knock sensors are capable of producing a correct AC signal.

    4.

  4. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

2

Important:: If an engine knock can be heard, repair the engine mechanical problem before proceeding with this diagnostic. Refer to Engine Noise Diagnosis in Engine Mechanical .

  1. Operate engine within conditions specified in Conditions for Setting the DTC.
  2. Using a scan tool, monitor Specific DTC info for DTC P0326 until the DTC P0326 test runs.

Does the scan tool indicate DTC P0326 failed this ignition?

--

Go to Step 4

Go to Step 3

3
  1. Turn ON the ignition switch.
  2. Review and record scan tool Fail Records data for DTC P0326.
  3. Operate vehicle within Fail Records conditions.
  4. Using a scan tool, monitor Specific DTC info for DTC P0326 until the DTC P0326 test runs.

Does the scan tool indicate DTC P0326 failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4
  1. Disconnect both knock sensor electrical connectors.
  2. Using a J 39200 Digital Multimeter, measure voltage between the KS signal circuit at each knock sensor and ground.

Does the Digital Multimeter indicate voltage at the specified value for both knock sensors?

5V

Go to Step 5

Go to Step 9

5

Digital Multimeter on 400K ohm scale, measure the resistance of each knock sensor by connecting the Digital Multimeter between the sensor terminal and the engine block.

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

100K ohms

Go to Step 6

Go to Step 10

6

  1. Connect the DVM to measure voltage between the Bank 1 knock sensor terminal and engine ground.
  2. Select 2 volts AC scale on the Digital Multimeter.
  3. Engine idling, observe the Digital Multimeter.
  4. Repeat the above test for the Bank 2 knock sensor.

Is any signal indicated on the Digital Multimeter for either knock sensor?

--

Go to Step 10

Go to Step 7

7

  1. Turn OFF the ignition switch.
  2. Digital Multimeter still connected to measure voltage between the knock sensor terminal and engine ground.
  3. Tap on the engine lift bracket while observing the Digital Multimeter.

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

--

Go to Step 8

Go to Step 10

8
  1. Check the KS signal circuit for incorrect routing near secondary wires or for a poor terminal connection at the knock sensor.
  2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 14

Go to Step 11

9
  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Turn ON the ignition switch.
  4. Check the KS signal circuit between the PCM and the knock sensor connector for the following conditions:
    5. • An open.
    • A short to voltage.
    • A short to ground.
  5. If a problem is found, repair as necessary. Refer to Wiring Repairs in Electrical Diagnosis.

Was a problem found?

--

Go to Step 14

Go to Step 11

10

Replace the affected knock sensor. Refer to Knock Sensor Replacement .

Is the action complete?

--

Go to Step 14

--

11
  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Check the KS signal circuit for a poor terminal connection at the PCM.
  4. If a problem is found, replace faulty terminal.

Was a problem found?

--

Go to Step 14

Go to Step 12

12
  1. Replace the KS module. Refer to Knock Sensor Module Replacement .
  2. Operate the engine within conditions specified in Conditions for Setting the DTC.
  3. Using a scan tool, monitor Specific DTC info for DTC P0326 until the DTC P0326 test runs.

Does scan tool indicate DTC P0326 failed this ignition?

--

Go to Step 13

Go to Step 14

13

Replace the PCM.

Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is action complete?

--

Go to Step 14

--

14
  1. Review and record Fail Records data
  2. Clear DTCs.
  3. Operate the vehicle within Fail Records conditions.
  4. Using a scan tool, monitor Specific DTC info for DTC P0326 until the DTC P0326 test runs.

Does the scan tool indicate DTC P0326 failed this ignition?

--

Go to Step 2

System OK