3176C, 3406E and 3456 Industrial Engines Troubleshooting – Sensor Signal (PWM) – Test

System Operation Description:

Use this procedure to troubleshoot the electrical system if a problem is suspected with the Pulse Width Modulated (PWM) auxiliary temperature sensor.

System Operation

The PWM sensor provides a signal to the engine’s Electronic Control Module (ECM). The sensor receives a 8.0 ± 0.4 VDC regulated voltage from the ECM.

The sensor’s wires are routed from the ECM to the sensor connectors. The following list gives the terminal locations for the sensor connector.

 

  • Terminal A 8 V supply
  • Terminal B sensor return
  • Terminal C sensor signal

The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Test Step 1. Inspect the Electrical Connectors and the Wiring

 

  1. Remove electrical power from the ECM.


Illustration 2 g01139425
ECM
(1) J1/P1 connectors
(2) J2/P2 connectors

Thoroughly inspect the J1/P1 and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.

Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.


Illustration 3 g01462108
P1 ECM connector
(P1-29) Digital return
(P1-35) +8 V supply


Illustration 4 g01462067
P2 ECM connector
(P2-24) Auxiliary temperature sensor


Illustration 5 g01159881
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal

  1. Perform a 45 N (10 lb) pull test on each of the wires in the circuit.

 

  1. Check the allen head screw from each ECM connector for the proper torque. Refer to Troubleshooting, “Electrical Connectors – Inspect” for the correct torque value.

 

  1. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All of the connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

 

  • OK – The harness and connectors appear to be OK. Proceed to Test Step 2. 
  • Not OK – The connectors and/or wiring are not OK.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

    STOP

Test Step 2. Check the Digital Supply Voltage at the Sensor Connector

 

  1. Remove electrical power from the ECM.

 

  1. Disconnect the suspect sensor at the sensor connector.

 

  1. Restore electrical power to the ECM.

 

  1. Measure the voltage on the ECM side of the sensor connector between pin A and pin B for the suspect sensor.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

 

  • OK – The supply voltage is 8.0 ± 0.4 VDC. Proceed to Test Step 4. 
  • Not OK – The supply voltage is not 8.0 ± 0.4 VDC. Proceed to Test Step 3.

Test Step 3. Check the Digital Supply Voltage at the ECM

 

  1. Remove electrical power from the ECM.

 

  1. Remove the supply wire from P1-35. Install a wire jumper into the socket for P1-35.

 

  1. Restore electrical power to the ECM.

 

  1. Measure the voltage between the wire jumper in terminal P1-35 and engine ground.

 

  1. Remove electrical power from the ECM.

 

  1. Remove the wire jumper and reconnect all wires. Reconnect ECM connector J1/P1.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

 

  • OK – The supply voltage is 8.0 ± 0.4 VDC. The supply voltage at the ECM is correct. There is a problem in the wiring between the ECM and the sensor connector. Repair the connectors or wiring and/or replace the connectors or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

    STOP

     

  • Not OK – The supply voltage is not 8.0 ± 0.4 VDC. The voltage at the ECM is not correct.Repair: Replace the ECM. Refer to Troubleshooting, “ECM – Replace”. Verify that the problem is resolved.

    STOP

Test Step 4. Check the Digital Sensor’s Signal Frequency and the Duty Cycle at the Sensor Connector

 

  1. Remove electrical power from the ECM.

 

  1. Remove the sensor’s signal wire from pin C of the sensor connector.

 

  1. Reconnect the sensor connector.

 

  1. Restore electrical power to the ECM.Note: Set the multimeter to “VDC”. Press the “Hz” button twice so that the % symbol is displayed.

 

  1. Measure the frequency and the duty cycle between the sensor’s signal wire and pin B of the digital sensor at the sensor connector.

 

  1. Remove electrical power from the ECM.

 

  1. Replace the sensor’s signal wire and reconnect the sensor.

Expected Result:

The duty cycle is between 10 to 90 percent. The frequency reading is approximately 500 Hz.

Results:

 

  • OK – The frequency and the duty cycle are correct. Proceed to Test Step 5. 
  • Not OK – The frequency or the duty cycle is not correct.Repair: Replace the sensor. Verify that no diagnostic codes are active for the suspect sensor before permanently installing the sensor.

    STOP

Test Step 5. Check the Sensor’s Duty Cycle at the ECM

 

  1. Remove the signal wire for the sensor from ECM connector P2. Refer to Illustration 1 for the terminal locations for the ECM connector.

 

  1. Restore electrical power to the ECM.

 

  1. Measure the duty cycle between the sensor’s signal wire and the sensor’s return wire.Note: Set the multimeter to “VDC”. Press the “Hz” button twice so that the % symbol is displayed.

 

  1. Remove electrical power from the ECM. Reconnect all wires.

Expected Result:

The duty cycle is between 10 to 90 percent.

Results:

 

  • OK – The duty cycle is correct.Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, “ECM – Replace”.

    STOP

     

  • Not OK – The duty cycle is not correct.Repair: There is a problem in the wiring between the ECM and the connector for the sensor. Repair the connectors and/or wiring between the ECM and the connector for the sensor.

    STOP

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