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Electronic Control System Gas Plus Engines – FAULT CODE 572

Knock Sensor Circuit – Shorted Low, Front Sensor

Overview

CODE REASON EFFECT
Fault Code: 572
PID: S91
SPN: 1353
FMI: 4
LAMP: Amber
SRT: 

Knock Sensor Circuit – Shorted Low, Front Sensor. Knock sensor circuit shorted low.

Knock control will be disabled.

Knock Sensor 1 and 2 Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) uses this sensor to determine if the engine is knocking so it can protect the engine.

Component Location

The knock sensor 1 is located on the side of the engine, on the block, above the air compressor on the C and L Gas Plus engines. The B series engine has Knock Sensor 1 located on the cylinder head intake cover capscrew.

Knock Sensor 2 is located on the top of the engine, on the cylinder head, beside cylinder number 6 on the C and L Gas Plus engines. On B series engine, Knock Sensor 2 is located on the left side of the block near the ECM.

Cautions and Warnings

 CAUTION 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.
 CAUTION 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Read the fault codes. Fault Code 572 active?
STEP 2. Check the knock sensor.  
  STEP 2A. Inspect the engine harness and knock sensor connector pins. Dirty or damaged pins?
  STEP 2B. Read the fault codes. Fault Code 572 active?
STEP 3. Check the engine harness.  
  STEP 3A. Inspect the engine harness and ECM connector pins. Dirty or damaged pins?
  STEP 3B. Read the fault codes. Fault Code 572 active?
  STEP 3C. Check for an open circuit. Less than 10 ohms?
  STEP 3D. Check for a short circuit to ground. Greater than 100k ohms?
  STEP 3E. Check for a short circuit from pin to pin. Greater than 100k ohms?
  STEP 3F. Check for an inactive fault code. Fault Code 572 inactive?
STEP 4. Clear the fault codes.  
  STEP 4A. Disable the fault code. Fault Code 572 inactive?
  STEP 4B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Read the fault codes.

Conditions

  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 572 active?
YES NO
No Repair No Repair

Guided Step 2 – Check the knock sensor.

Guided Step 2A – Inspect the engine harness and knock sensor connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from knock sensors 1 and 2.

Action

  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Wire insulation damaged
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Connector shell broken
  • Dirt or debris in or on the connector pins.

Refer to the circuit diagram or wiring diagram for component pin identification.

For general inspection techniques, refer to Component Connector and Pin Inspection, Procedure 019-361.

Dirty or damaged pins?
YES NO

Repair the damaged pins. Repair or replace the engine harness, or replace the sensor, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Install the appropriate connector seal if it is damaged or missing.
  • Repair the engine harness. Refer to Procedure 019-214.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Replace the sensor. Refer to Procedure 019-346.
 No Repair

Guided Step 2B – Read the fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for one minute.
  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 572 active?
YES NO
No Repair No Repair

Guided Step 3 – Check the engine harness.

Guided Step 3A – Inspect the engine harness and ECM connector pins.

Conditions

  • Turn keyswitch OFF.
  • Disconnect engine harness connector 1 and connector 2 from the ECM.

Action

  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Wire insulation damaged
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Connector shell broken
  • Dirt or debris in or on the connector pins.

Refer to the circuit diagram or wiring diagram for component pin identification.

For general inspection techniques, refer to Component Connector and Pin Inspection, Procedure 019-361.

Dirty or damaged pins?
YES NO

Repair the damaged pins. Repair or replace the engine harness, or replace the ECM, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Install the appropriate connector seal if it is damaged or missing.
  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Replace the ECM. Call for pre-authorization. Refer to Procedure 019-031.
 No Repair

Guided Step 3B – Read the fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for 1 minute.
  • Read the fault codes using INSITE™.

Fault Code 572 active?
YES NO
No Repair No Repair

Guided Step 3C – Check for an open circuit.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness connector 2 from the ECM
  • Disconnect the engine harness from knock sensors 1 and 2.

Action

  • Measure the resistance between the knock 1 positive (+) pin in the engine harness ECM connector to the knock 1 positive (+) pin in the sensor harness connector.
  • Measure the resistance between the knock 1 negative (-) pin in the engine harness ECM connector to the knock 1 negative (-) pin in the sensor harness connector.
  • Measure the resistance between the knock 2 positive (+) pin in the engine harness ECM connector to the knock 2 positive (+) pin in the sensor harness connector.
  • Measure the resistance between the knock 2 negative (-) pin in the engine harness ECM connector to the knock 2 negative (-) pin in the sensor harness connector.

Refer to the circuit diagram or wiring diagram for component pin identification.

For general resistance measurement techniques, refer to the Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360.
SMALL | MEDIUM | LARGE

Less than 10 ohms?
YES NO
No Repair

Repair or replace the engine harness.

  • Repair the engine harness. Refer to Procedure 019-214 or 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3D – Check for a short circuit to ground.

Conditions

  • Turn keyswitch OFF.
  • Disconnect engine harness connector 2 from the ECM.
  • Disconnect the engine harness from knock sensors 1 and 2.

Action

  • Measure the resistance between the knock 1 Positive (+) pin in the engine harness ECM connector to engine block ground.
  • Measure the resistance between the knock 2 Positive (+) pin in the engine harness ECM connector to engine block ground.

Refer to the circuit diagram or wiring diagram for component pin identification.

For general resistance measurement techniques, refer to the Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360.
SMALL | MEDIUM | LARGE

Greater than 100k ohms?
YES NO
No Repair

Repair or replace the engine harness.

  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3E – Check for a short circuit from pin to pin.

Conditions

  • Turn keyswitch OFF.
  • Disconnect engine harness connector 1 and connector 2 from the ECM.
  • Disconnect the engine harness from knock sensors 1 and 2.

Action

  • Measure the resistance between the knock 1 positive (+) pin in engine harness ECM connector 2 to all other pins in the connector.
  • Measure the resistance from the knock 1 positive (+) pin in engine harness ECM connector 2 to all pins in engine harness ECM connector 1.
  • Measure the resistance between the knock 2 positive (+) pin in engine harness ECM connector 2 to all other pins in the connector.
  • Measure the resistance from the knock 2 positive (+) pin in engine harness ECM connector 2 to all pins in engine harness ECM connector 1.

Refer to the circuit diagram or wiring diagram for component pin identification.

For general resistance measurement techniques, refer to the Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360.
SMALL | MEDIUM | LARGE

More than 100k ohms?
YES NO
No Repair

Repair or replace the engine harness.

  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3F – Check for an inactive fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 572 inactive?
YES NO
No Repair

Replace the ECM. Call for pre-authorization. Refer to Procedure 019-031.

Guided Step 4 – Clear the fault codes.

Guided Step 4A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for one minute.
  • Use INSITE™ electronic service tool to verify that Fault Code 572 is inactive.

Fault Code 572 inactive?
YES NO
No Repair No Repair

Guided Step 4B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to erase the inactive fault codes.

All fault codes cleared?
YES NO
No Repair No Repair
Repair complete
Appropriate troubleshooting charts
Last Modified:  03-Sep-2004
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