GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Cavalier 🢒 DTC 🢒 DTC P0325 Knock Sensor (KS) Circuit

Object Number: 50810 Size: SF
Engine Controls Components
Ignition Controls
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

The knock sensor (KS) system detects for an engine detonation. The knock sensor produces an AC voltage signal. The amplitude and the frequency of the AC voltage signal is dependent upon the knock level being detected. This signal then travels to the KS module that is an internal part of the Powertrain Control Module (PCM). If knock is detected, the PCM will retard the spark timing based on the signal from the knock sensor.

Conditions for Setting the DTC
    • Engine run time is greater than 20 seconds.
    • Engine Coolant Temperature (ECT) is greater than 56°C (131°F).
    • Engine speed is above 1600 RPM.
    • MAP is greater than 60 kPa.
    • Engine vacuum is less than 33 kPa.
    • The KS voltage and variation is not within normally expected ranges.
    • The above conditions are present for greater than 60 seconds.

Action Taken When the DTC Sets
    • The Malfunction Indicator Lamp (MIL) will illuminate.
    • The PCM will record operating conditions at the time the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.
    • A history DTC stores.
    • The coolant fan turns ON.
    • The PCM will default to 6 degrees timing.

Conditions for Clearing the MIL/DTC
    • The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • The MIL/DTCs can be cleared by using the scan tool.

Diagnostic Aids
    • Check and correct any abnormal engine noise before using the diagnostic table.
    • Thoroughly check any suspected circuitry for the following conditions:
       - Backed out terminals
       - Improper mating
       - Broken locks
       - Improperly formed connectors
       - Damaged terminals
       - Poor terminal to wiring connections
       - Physical damage to the wiring harness

Test Description

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

  1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when this DTC is set. The scan tool stores this data for later reference.

    2.

  2. If the engine has an internal knock or an audible noise that causes a knocking type of noise on the engine block, this is an indication that the knock sensor may be responding to the noise.

    3.

  3. This step checks the internal resistance of the PCM or the wiring to the knock sensor electrical connector.

    4.

  4. Thoroughly check any suspected circuitry for the following conditions:

    5. • Backed out terminals
    • Improper mating
    • Broken locks
    • Improperly formed or damaged terminals
    • Poor terminal to wiring connections

  5. Reprogram the replacement PCM and perform the crankshaft position system variation learning procedure. Refer to PCM Replacement/Programming for PCM programming andCKP System Variation Learn Procedure for the crankshaft position variation learning procedure.

DTC P0325-Knock Sensor (KS) Circuit

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check for 2.4L or Powertrain On Board Diagnostic (OBD) System Check for 2.2L

2

  1. Start the engine.
  2. Listen to the engine while raising and lowering the engine speed.

Is a knock or audible noise present?

--

Go to Step 3

Go to Step 4

3
  1. Turn OFF the ignition switch.
  2. Check for the following conditions:
    3. • Mechanical engine problem
    • Loose bracket
    • Loose component
  3. Repair the conditions as necessary.

Was a repair necessary?

--

Go to Step 12

Go to Diagnostic Aids

4
  1. Turn OFF the ignition switch.
  2. Disconnect the knock sensor electrical connector.
  3. Connect a test light to B+.
  4. Probe the knock sensor Reference Low circuit at the knock sensor electrical connector (PCM side) with the test light. The test light should illuminate.

Does the test light illuminate?

--

Go to Step 5

Go to Step 6

5

  1. Connect a DMM between the knock sensor electrical connector cavities (PCM side).
  2. Observe the resistance on the DMM.

Is the resistance between the specified values?

95K -105K ohms

Go to Step 9

Go to Step 7

6
  1. Check the knock sensor ground circuit for an open circuit. Refer to Wiring Repairs in Wiring Systems.
  2. Repair the circuit as necessary.

Was a repair necessary?

--

Go to Step 12

Go to Step 8

7
  1. Check the knock sensor signal circuit for the following conditions:
    2. • Open circuit
    • Short to ground
    • Short to voltage
  2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 8

8

  1. Check the knock sensor circuits for a poor electrical terminal connection(s) at the PCM.
  2. Repair the electrical terminal connection(s) as necessary. Refer to Connector Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 11

9
  1. Check the knock sensor electrical connector for a poor electrical terminal connection(s).
  2. Repair the electrical terminal connection(s) as necessary. Refer to Connector Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 10

10
  1. Replace the knock sensor (KS). Refer to Knock Sensor Replacement .
  2. Turn ON the ignition switch leaving the engine OFF.
  3. Clear the DTCs with the scan tool.
  4. Start the engine.
  5. Operate the vehicle within the Conditions For setting the DTC in order to check to see if the DTC resets.

Does the DTC reset?

--

Go to Step 11

Go to Step 13

11

  1. Turn OFF the ignition switch.
  2. Replace the PCM. Refer to PCM Replacement .

Is the action complete?

--

Go to Step 12

--

12
  1. Turn ON the ignition switch leaving the engine OFF.
  2. Clear the DTCs with the scan tool.
  3. Start the engine.
  4. Idle the engine at the normal operating temperature.
  5. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has ran and passed?

--

Go to Step 13

Go to Step 2

13

Check to see if any DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to the applicable DTC table

System OK