For 1990-2009 cars
Engine Controls Components
Ignition Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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 knock is occurring by comparing the signal level on the KS circuit with the voltage level on the noise channel. The noise channel allows the PCM to reject any false knock signal by indicating 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 VSS, TP sensor, ECT sensor DTC(s) set.

• | Engine has been running for at least 10 seconds.

• | Engine coolant temperature is greater than 65°C (149°F).

• | Throttle angle is greater than 10%.

• | Engine speed is between 2200 RPM and 2500 RPM.

• | Noise channel voltage level above 4.8 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 Failure Records data only. This information will not be stored as Freeze Frame data.

### 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 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. Checks that the fault is present.

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

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

#### DTC P0326 - Knock Sensor (KS) Circuit Range/Performance

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to 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.

1. Operate engine within conditions specified in diagnostic support Conditions for Setting the DTC.
2. 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 ign?

--

Go to Step 4

Go to Step 3

3 |

1. Ignition ON, engine OFF, review and record scan tool Fail Records data for DTC P0326.
2. Operate vehicle within Fail Records conditions.
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 ign?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect both knock sensor electrical connectors.
2. Using a DVM (J 39200), measure voltage between the KS signal circuit at the knock sensor and ground.

Does DVM indicate voltage at the specified value for knock sensor?

Approx. 5.0 volts

Go to Step 5

Go to Step 9

5 | Using a DVM on the 400K ohm scale, measure the resistance of knock sensor by connecting the DVM between the sensor terminal and the engine block. Is resistance of knock sensor near the specified value? | 100 K ohms | Go to Step 6 | Go to Step 10
6 |

1. Connect DVM to measure voltage between the Bank 1 knock sensor terminal and engine ground.
2. Select 2 volts AC scale on DVM.
3. Engine idling, observe DVM.

Is any signal indicated on the DVM for knock sensor?

--

Go to Step 10

Go to Step 7

7 |

1. Ignition OFF, DVM still connected to measure AC voltage between the knock sensor terminal and engine ground.
2. Tap on engine lift bracket while observing DVM.

Is any signal indicated on the DVM 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. Ignition OFF, disconnect the PCM.
2. Ignition ON, check the KS signal circuit between the PCM and the knock sensor connector for an open, a short to voltage, or a short to ground.
3. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis Section 8A.

Was a problem found?

--

Go to Step 14

Go to Step 11

10 | Replace the affected knock sensor. Is action complete? | -- | Go to Step 14 | --
11 |

1. Ignition OFF, disconnect the PCM.
2. Check the KS signal circuit for a poor terminal connection at the PCM.
3. 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.
2. Operate engine within conditions specified in diagnostic support 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 ign?

--

Go to Step 13

Verify repair

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 vehicle within Fail Records conditions.
4. 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 2

Repair complete. If a driveability symptom still exists, go to Symptoms