DTC P0325 Knock Sensor (KS) Circuit. Oldsmobile Alero 2000

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 2000 🢒 Alero 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 DTC P0325 Knock Sensor (KS) Circuit

Engine Controls Components
Power, Ground, KS, CMP, CKP, Coils, and ICM
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 KS produces an AC voltage signal. The amplitude and the frequency of the AC voltage signal is dependent upon the knock level being detected. If knock is detected, the PCM will retard the spark timing based on the signal from the KS.

Conditions for Running the DTC

•	The engine run time is more than 20 seconds.

•	The engine coolant temperature (ECT) is more than 70°C (158°F).

•	The engine speed is between 1800-2400 RPM.

•	The manifold absolute pressure (MAP) is more than 35 kPa.

•	The engine vacuum is between 33-45 kPa.

Conditions for Setting the DTC

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

•	The above conditions are present for more than 15 seconds.

Action Taken When the DTC Sets

•	The malfunction indicator lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

•	The PCM records the operating conditions at the time when the diagnostic fails. This information stores in the Freeze Frame and Failure Records buffers.

•	A history DTC stores.

•	The coolant fan turns on.

Conditions for Clearing the DTC

•	The 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.

•	The DTC can be cleared by using the scan tool.

Diagnostic Aids

•	Correct any abnormal engine noise before using the diagnostic table.

•	Thoroughly inspect any suspected circuitry for the following conditions:

-	Any backed out terminals

-	Any incorrect mating

-	Any broken locks

-	Any incorrectly formed connectors

-	Any damaged terminals

-	Any poor terminal-to-wiring connections

-	Any physical damage to the wiring harness

•	Test the KS for the proper torque.

•	Inspect the KS mounting location between the sensor and the engine mounting face for the following conditions:

Any burrs

-	Any casting flash

-	Any other foreign material

•	Verify that the KS head is clear of contact with any of the following items:

The hoses

-	The brackets

-	The engine electrical wiring

•	Inspect the KS wiring for the correct twisting of the wiring. The wiring for should have a minimum of 9 twists per foot. This twisting of the wiring reduces electrical noise on the KS circuit, lessening the chance of erratic signals to the PCM.

Test Description

The numbers below refer to step numbers on the diagnostic table.

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

This step tests the internal resistance of the PCM and the wiring to the knock sensor connector.

The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.

DTC P0325-Knock Sensor (KS) Circuit

Step

Action

Values

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

Start the engine.
Listen to the engine while increasing and decreasing the engine speed.

Can a knock or a noise be heard?

Go to Step 3

Go to Step 4

Turn off the ignition.
Inspect for the following conditions:

•	Any engine mechanical problems

•	A loose bracket

•	Any loose components

If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 12

Go to Diagnostic Aids

Turn off the ignition.
Disconnect the knock sensor connector.
Connect a test lamp to B+.
Probe the knock sensor Reference Low circuit at the knock sensor connector on the PCM side with the test lamp.

Does the test lamp illuminate?

Go to Step 5

Go to Step 6

Connect a DMM between the knock sensor signal circuit and Reference Low circuit at the knock sensor connector on the PCM side.
Observe the resistance on the DMM.

Is the resistance within the specified range?

95K -105K ohms

Go to Step 9

Go to Step 7

Test the knock sensor Reference Low circuit for an open.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

Test the knock sensor signal circuit for the following conditions:

•

An open

•	A short to ground

•	A short to voltage

If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

Inspect the knock sensor circuit for poor connections at the PCM.
If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

Inspect the knock sensor connector for poor connections.
If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

Replace the knock sensor. Refer to Knock Sensor Replacement .

Did you complete the repair?

Go to Step 12

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

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 12

Use a scan tool to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 3

System OK