Circuit Description
The Knock Sensor (KS) system detects engine detonation. The PCM retards
the spark timing based on the signals from the knock sensors. The knock sensors
produce an AC voltage. The knock sensor voltages are an input to the PCM.
The amount of AC voltage produced is proportional to the amount of knock.
An operating engine produces a normal amount of engine mechanical vibration
(noise). The knock sensors produce an AC voltage signal from this noise. When
an engine operates, the PCM learns the minimum and maximum frequency of the
noise the engine produces. When the PCM determines that this frequency is
less than or greater than the expected amount, a knock sensor DTC will set.
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
|
2
|
ImportantIf an engine knock can be heard, repair the engine mechanical problem
before proceeding with this diagnostic.
- Turn ON the ignition leaving the engine OFF.
- Review the Freeze Frame and/or Failure Records data for this DTC
and observe the parameters.
- Turn OFF the ignition for 15 seconds.
- Start the engine.
- Operate the vehicle within the conditions required for this diagnostic
to run, and as close to the conditions recorded in Freeze Frame and/or Failure
Records as possible. Special operating conditions that you need to meet before
the PCM will run this diagnostic, where applicable, are listed in Conditions
for Setting the DTC.
- Select the Diagnostic Trouble Code (DTC) option and the Specific
DTC option, then enter the DTC number using the scan tool.
Does the scan tool indicate that this diagnostic failed this ignition?
| --
|
Go to Step 3
| Refer to Diagnostic Aids
|
3
|
- Disconnect the knock sensor electrical connector located behind
the intake manifold.
- Measure the resistance of the rear knock sensor by connecting
the DMM between the rear knock sensor signal circuit on the sensor side and
the engine block using the DMM
.
- Set the DMM to the 400K ohm scale.
Is resistance of the knock sensor within the specified range?
| 93-107Kohms
|
Go to Step 4
|
Go to Step 6
|
4
|
- Connect the DMM
between the rear knock sensor signal circuit on the sensor side and
the engine block.
- Set the DMM to the AC voltage scale.
- Tap on the rear of the engine while observing the signal indicated
on the DMM.
Is any signal indicated on the DMM while tapping on the engine near
the Knock Sensor?
| --
|
Go to Step 5
|
Go to Step 7
|
5
|
- Disconnect the PCM connector located on the same side as the manufacturers
logo. Refer to
PCM/TAC Module Replacement
.
- Check the KS signal circuit between the PCM and the knock sensor
connector for the following:
- An open.
- A short to voltage.
- A short to ground.
Was a problem found and corrected?
| --
|
Go to Step 10
|
Go to Step 8
|
6
|
- Remove the intake manifold. Refer to Engine/Engine
Mechanical.
- Check for an open or short to ground in the signal circuit between
the knock sensor jumper harness connector located at the back of the intake
manifold and the knock sensor connector.
Was a problem found and corrected?
| --
|
Go to Step 10
|
Go to Step 7
|
7
| Replace the Knock Sensor.
Refer to
Knock Sensor (KS) Replacement
.
Is the action complete?
| --
|
Go to Step 10
| --
|
8
| Check the KS signal
circuit for a poor terminal connection at the PCM. Refer to Body and Accessories/Wiring Systems.
Was a problem found and corrected?
| --
|
Go to Step 10
|
Go to Step 9
|
9
|
Important:Program the replacement PCM. Refer to
PCM/TAC Module Replacement
.
Replace the PCM.
Is the action complete?
| --
|
Go to Step 10
| --
|
10
|
- Select the Diagnostic Trouble Code (DTC) option and the Clear
DTC Information option using the scan tool.
- Idle the engine at the normal operating temperature.
- Select the Diagnostic Trouble Code (DTC) option and the Specific
DTC option, then enter the DTC number using the scan tool.
- Operate the vehicle within the conditions for setting this DTC
as specified in the supporting text, if applicable.
Does the scan tool indicate that this test ran and passed?
| --
|
Go to Step 11
|
Go to Step 2
|
11
| Select the Capture Info option and the Review Info option using the scan tool.
Does the scan tool display any DTCs that you have not diagnosed?
| --
| Go to the applicable DTC table
| System OK
|