On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

DG: Knock Sensor (KS)

DG1 DTC P0330, P0331 (KS2), DTC P0325, P0326 (KS1): CHECK VOLTAGE BETWEEN SENSOR AND SIG RTN

Verify that KS is connected and installed properly. Then complete comprehensive repair verification drive cycle.
Key on, engine off.
Access KS PID.
Read dc voltage.

Is the KS PID less than 0.5 volts?

Yes	No
KEY OFF. GO to DG2 .	GO to DG5 .

DG2 CHECK KS SENSOR RESISTANCE

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect KS.
For 4.2L: Measure resistance between (KS+) and (KS-) at the knock sensor.

Is resistance between 4.39 and 5.35 megohm?

Yes	No
All others: GO to DG7 . For Town Car, 5.4L E/F-Series (HD), and 6.8L E/F-Series: GO to DG6 .	For resistance greater than 5.35 megohm: GO to DG3 . For resistance less than 4.39 megohm: GO to DG4 .

DG3 CHECK FOR OPEN OF KS CIRCUIT BETWEEN KS SIGRTN AND SHIELD IN HARNESS

Disconnect PCM.
Measure resistance of the KS+ circuit between the PCM harness connector pin and the KS harness connector.
For 4.2L:
Measure resistance of KS- circuit between the PCM harness connector pin and the KS connector.
Where applicable, measure resistance of shield between the PCM harness connector and the shield pin at the KS connector.

Is each resistance less than 5.0 ohms?

Yes	No
REPLACE KS.	REPAIR open circuit. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)

DG4 CHECK KS CIRCUIT FOR SHORT TO GROUND IN HARNESS

Disconnect PCM.
Measure resistance between the KS- circuit at the PCM harness connector and chassis GND.
Measure resistance between the KS+ circuit at the PCM harness connector and chassis GND.
For 4.2L Only:
Measure resistance between the KS- and KS+ at the PCM harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
GO to DG7 .	SERVICE short circuit. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)

DG5 CHECK KS CIRCUITS FOR SHORT TO POWER IN HARNESS

Disconnect PCM.
Key on.
Measure voltage between the KS+ circuit at the PCM harness connector and battery negative post.
For 4.2L Only:
Measure voltage between the KS- circuit at the PCM harness connector and battery negative post.

Is each voltage less than 0.5 volt?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)	SERVICE short circuit. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (Refer to Section 2 , Drive Cycles.)

DG6 CHECK SHIELD CIRCUIT RESISTANCE

Disconnect PCM.
Measure resistance of the KS shield between the PCM harness connector pin and the KS harness connector.

Is resistance less than 5.0 ohms?

Yes	No
GO to DG7 . COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)	REPAIR open circuit. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)

DG7 CHECK PCM FOR SHORT TO GROUND

Measure resistance between KS+ and SIG RTN circuits at the KS harness connector.
For 4.2L Only:
Measure resistance between KS+ and KS- circuits at the PCM harness connector.

Is resistance greater than 10,000 ohms?

Yes	No
REPLACE KS. If concern is still present, REPLACE PCM (refer to Section 2 , Flash EEPROM). COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)	REPLACE PCM (refer to Section 2 , Flash EEPROM). COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)

DG15 DTC P0325, P0326 (KS1), DTC P0330, P0331 (KS2): CHECK KS SENSOR VOLTAGE

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Access KS PID.
Key on, engine off.

Is the KS PID between 2.2 and 2.6 volts?

Yes	No
KEY OFF. GO to DG16 .	GO to DG18 .

DG16 CHECK KS CIRCUIT FOR INTERMITTENT FAULT

Key on.
While viewing the voltmeter, grasp the vehicle harness as close to the knock sensor(s) as possible. Shake and bend a small section of the harness from the KS sensor to the PCM.
Tap the PCM and KS connectors if possible.

Is KS reading changing?

Yes	No
ISOLATE fault and SERVICE as required. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)	GO to DG17 .

DG17 CHECK FOR KS VOLTAGE INCREASE

Start and run engine.
Monitor voltage at the knock sensor at idle and at 3000 rpm.

Does the AC voltage reading increase?

Yes	No
For symptom only: RETURN to Section 3 . All others with DTC: REPLACE PCM (refer to Section 2 , Flash EEPROM). COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)	GO to DG18 .

DG18 CHECK KS CIRCUIT FOR OPEN IN HARNESS

PCM disconnected.
Disconnect suspect KS.
Measure resistance of the KS+ signal circuit between the PCM harness connector pin and the KS harness connector.
Measure resistance of the SIG RTN circuit between the PCM harness connector and the KS harness connector.

Is each resistance less than 5.0 ohms?

Yes	No
GO to DG19 .	REPAIR open circuit. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)

DG19 CHECK KS CIRCUIT FOR SHORT TO GROUND

Measure resistance of the KS+ circuit between the PCM harness connector pin and chassis GND.

Is resistance greater than 10,000 ohms?

Yes	No
REPLACE suspect KS. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)	REPAIR short circuit. COMPLETE Comprehensive Component Repair Verification Drive Cycle. (REFER to Section 2 , Drive Cycles.)