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Electronic Control System Gas Plus Engines – FAULT CODE 753 – L Gas Plus

Engine Speed/Position Camshaft Synchronization Error

Overview

CODE REASON EFFECT
Fault Code: 753
PID: S064
SPN: 723
FMI: 2
LAMP: Amber
SRT: 

Engine Speed/Position Camshaft Synchronization Error. Invalid engine speed signal detected on the engine position sensor signal pins in the ECM connector.

Engine can die or will not start.

Engine Position Sensor Circuit
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Circuit Description

The camshaft engine speed/position sensor provides engine speed information to the electronic control module (ECM). The sensor is powered by 5 volts. The sensor generates the signal by sensing the movement of target teeth machined into a tone wheel that is mounted to the camshaft.

Component Location

The camshaft speed/position sensor is located on the intake side of the engine above the accessory drive. Refer to Procedure 100-002 for a detailed component location view.

Shop Talk

This fault code is recorded when the ECM does not receive a signal from the camshaft engine speed sensor, or the signal it receives is degrading.

Possible causes of this fault code include: open circuit on the supply, signal, or return circuits in the sensor, engine harness, or ECM.

Short circuits to ground or return circuits in the sensor, engine harness, or ECM.

Short circuits to a voltage source in the sensor, engine harness, or ECM.

Damage to the sensor target teeth or tone wheel.

If this fault code occurs intermittently, look closely for causes of intermittent harness connections such as loose or worn pins in the engine harness connectors.

Cautions and Warnings

 CAUTION 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3823996 – female Weather-Pack test lead.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Check for sensor supply fault codes. Fault Code 352 or 386 active?
  STEP 1B. Check for an inactive fault code. Fault Code 753 inactive?
STEP 2. Check the camshaft speed/position sensor and circuit.  
  STEP 2A. Inspect the camshaft speed/position sensor and connector pins. Dirty or damaged pins?
  STEP 2B. Check the sensor supply voltage and return circuit. 4.75 to 5.25 VDC?
  STEP 2C. Inspect the camshaft speed/position sensor. Damage sensor tip?
  STEP 2D. Verify adequate camshaft speed/position senor air gap. Distance is between 30.16 mm [1.19 in] and 31.27 mm [1.23 in]?
STEP 3. Check the ECM and engine harness.  
  STEP 3A. Inspect the ECM and engine harness connector pins. Dirty or damaged pins?
  STEP 3B. Check for an inactive fault code. Fault Code 753 inactive?
  STEP 3C. Check for an open circuit in the engine harness. Less than 10 ohms?
  STEP 3D. Check for a pin to pin short circuit in the engine harness. Greater than 100k ohms?
  STEP 3E. Check for a pin to pin short circuit in the engine harness. Greater than 100k ohms?
  STEP 3F. Check for a pin short circuit to ground. Greater than 100k ohms?
  STEP 3G. Check for an inactive fault code. Fault Code 753 inactive?
STEP 4. Clear the fault codes.  
  STEP 4A. Disable the fault code. Fault Code 753 inactive?
  STEP 4B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Check for sensor supply fault codes.

Conditions

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

Action

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

Fault Code 352 or 386 active?
YES NO
No Repair No Repair
Fault Code 352 or 386

Guided Step 1B – Check for an inactive fault code.

Conditions

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

Action

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

Fault Code 753 inactive?
YES NO
No Repair No Repair
Procedure 019-362

Guided Step 2 – Check the camshaft speed/position sensor and circuit.

Guided Step 2A – Inspect the camshaft speed/position sensor and connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect camshaft speed/position sensor from the engine harness.

Action

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

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

Dirty or damaged pins?
YES NO

A defective connection has been detected in the sensor or harness connection.

Repair the damaged pins. Replace the engine harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Replace the heated oxygen sensor. Refer to Procedure 019-365.
 No Repair

Guided Step 2B – Check the sensor supply voltage and return circuit.

Conditions

  • Turn keyswitch OFF
  • Disconnect camshaft speed/position sensor from the engine harness
  • Turn keyswitch ON.

Action

  • Measure the voltage between the camshaft speed/position SUPPLY pin and the camshaft speed/position RETURN pin at the camshaft speed/position sensor connector of the engine harness.

Refer to the circuit diagram or wiring diagram for component pin identification.
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4.75 to 5.25 VDC?
YES NO
No Repair No Repair

Guided Step 2C – Inspect the camshaft speed/position sensor.

Conditions

  • Turn keyswitch OFF
  • Remove the camshaft speed/position sensor from the engine.

Action

  • Damage sensor tip
  • Physical signs of the sensor touching the speed or position teeth.

Damaged sensor tip?
YES NO

A defective sensor has been detected.

Replace the camshaft speed/position sensor. Refer to Procedure 019-365.

Inspect the camshaft tone wheel/gear teeth for damage or spinning. Sensor clearance is between 30.16 mm [1.19 in] and 31.27 mm [1.23 in]. Refer to Procedure 001-013 in the Troubleshooting and Repair Manual, C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

 No Repair

Guided Step 2D – Verify adequate camshaft speed/position sensor air gap.

Conditions

  • Turn keyswitch OFF
  • Remove camshaft speed/position sensor from the engine.

Action

  • Measure the distance between the sensor mounting surface and the edge of the tone wheel.
SMALL | MEDIUM | LARGE

Distance is between 30.16 mm [1.19 in] and 31.27 mm [1.23 in]?
YES NO
No Repair

Inspect the camshaft tone wheel/gear teeth for damage or spinning. Refer to Procedure 001-013 in the Troubleshooting and Repair Manual, C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Guided Step 3 – Check the ECM and engine harness.

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

Conditions

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

Action

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

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

Dirty or damaged pins?
YES NO

A defective connection has been detected in the ECM connector 1 or engine harness connector.

Repair the damaged pins. Replace the engine harness.

 No Repair

Guided Step 3B – 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 753 inactive?
YES NO
No Repair No Repair

Guided Step 3C – Check for an open circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness from the ECM connector 1.
  • Disconnect the camshaft speed/position sensor from the engine harness.

Action

  • Measure the resistance between the ECM connector 1 RETURN pin and the camshaft speed/position sensor connector RETURN pin.
  • Measure the resistance between the ECM connector 1 SUPPLY pin and the camshaft speed/position sensor connector SUPPLY pin.
  • Measure the resistance between the ECM connector 1 SIGNAL pin and the camshaft speed/position sensor connector SIGNAL pin.

Shake and wiggle the harness to determine an intermittent connection.

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

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

Less than 10 ohms?
YES NO
No Repair

An open return current has been detected in the engine harness.

Repair the damaged pins. Replace the engine harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Repair the engine harness. Refer to Procedure 019-202.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3D – Check for a pin to pin short circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the ECM
  • Disconnect the camshaft speed/position sensor from the engine harness.

Action

  • Measure the resistance between the camshaft speed/position SIGNAL pin in the engine harness and all other pins in the engine connector 1.
  • Measure the resistance between the camshaft speed/position SIGNAL pin in the engine harness connector 1 and all other pins in the engine connector 2.

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

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

SMALL | MEDIUM | LARGE

Greater than 100k ohms?
YES NO
No Repair

A pin to pin short circuit on the signal line has been detected in the engine harness.

Repair the damaged pins. Replace the engine harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3E – Check for a pin to pin short circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the ECM
  • Disconnect the camshaft speed/position sensor from the engine harness.

Action

  • Measure the resistance between the camshaft speed/position sensor 5 volt SUPPLY pin in the engine harness connector 1 and all other pins in the ECM connector 1.
  • Measure the resistance between the camshaft speed/position sensor 5 volt SUPPLY pin in the engine harness connector 1 and all other pins in the ECM connector 2.

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

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

SMALL | MEDIUM | LARGE

Greater than 100k ohms?
YES NO
No Repair

A pin to pin short circuit on the supply line has been detected in the engine harness.

Repair the damaged pins. Replace the engine harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3F – Check for a pin short to ground.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the ECM
  • Disconnect the camshaft speed/position sensor from the engine harness.

Action

  • Measure the resistance between the camshaft speed/position SIGNAL pin in the engine harness ECM connector 1 and ground.

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

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

Greater than 100k ohms?
YES NO
No Repair

A pin to ground short circuit on the signal line has been detected in the engine harness.

Repair the damaged pins. Replace the engine harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.

Guided Step 3G – 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 753 inactive?
YES NO
No Repair No Repair

Guided Step 4 – Clear the fault codes.

Guided Step 4A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON or Run/Stop switch to the RUN position
  • 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 753 is inactive.

Fault Code 753 inactive?
YES NO
No Repair No Repair

Guided Step 4B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON or Run/Stop switch to the RUN position
  • 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:  22-Sep-2004
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