DTC P0325 Knock Sensor (KS) Circuit. Isuzu S/T Isuzu

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 4WD 🢒 DTC 🢒 DTC P0325 Knock Sensor (KS) Circuit

Engine Controls Components
Cell 20: 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 Running the DTC

•	Engine run time is more than 20 seconds.

•	Engine coolant temperature (ECT) is more than 56°C (131°F).

•	Engine speed is above 1600 RPM.

•	MAP is more than 60 kPa.

•	Engine vacuum is less than 33 kPa.

Conditions for Setting the DTC

•	The KS voltage and variation is not within normally expected ranges.

•	The above conditions are present for more 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. The Freeze Frame and Failure Records buffers will store this information.

•	A history DTC is stored

•	The PCM will default to a more conservative spark timing.

Conditions for Clearing the MIL/DTC

•	The malfunction indicator lamp (MIL) will turn OFF after 3 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.

•	Use a scan tool to clear the DTCs.

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 number(s) below refer(s) to the step number(s) on the Diagnostic Table.

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

If the conditions for the test as described above are met, a DTC P0325 will set and the MIL will illuminate.

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.

This step checks the internal resistance of the knock sensor or the wiring to the knock sensor.

Thoroughly check any suspected circuitry for the following conditions:

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminal to wiring connections

•	Physical damage to the wiring harness

Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communication System (ITCS) information for PCM programming and the Crankshaft Position System Variation Learn for the crankshaft position system variation learn procedure.

DTC P0325-Knock Sensor (KS) Circuit

Step

Action

Value(s)

Yes

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

Go to Step 2

Go to

Powertrain On Board Diagnostic (OBD) System Check

Turn ON the ignition switch leaving the engine OFF.
Install a scan tool.
Review the Freeze Frame data and record the parameters.
Start the engine.
Operate the vehicle within the Conditions For Setting the DTC as specified in the supporting text.

Does the Malfunction Indicator Lamp (MIL) illuminate?

Go to Step 3

Go to Step 11

Listen to the engine while raising and lowering the engine speed.

Is a knock or audible noise present?

Go to Step 4

Go to Step 5

Turn OFF the ignition switch.
Check and repair the following conditions:

•	Mechanical engine problem

•	Loose bracket

•

Component

Is the action complete?

Go to Step 11

Turn OFF the ignition switch.
Disconnect the PCM electrical connectors at the PCM.
Connect a DMM to ground.
Measure the resistance of the knock sensor through the knock sensor signal circuit (sensor side).

Is the measured value within the specified value?

90K-110Kohms

Go to Step 6

Go to Step 8

Check the knock sensor signal circuit for a poor electrical connection at the PCM.
Repair the circuit as necessary. Refer to the Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 11

Go to Step 7

Replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

Go to Step 11

Check the knock sensor electrical connector for a poor electrical connection.
Repair the electrical connector as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 11

Go to Step 9

Check the knock sensor signal circuit for the following conditions:

•	Open circuit

•	Short to ground

•	Short to voltage

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 11

Go to Step 10

Replace the Knock Sensor (KS). Refer to the Knock Sensor Replacement .

Is the action complete?

Go to Step 11

Clear the DTCs with the scan tool.
Start the engine.
Idle the engine at the normal operating temperature.
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 12

Go to Step 3

Check to see if any DTCs are set.

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

Go to applicable DTC table

System OK