3176C, 3406E and 3456 Industrial Engines Troubleshooting – Sensor Supply – Test

System Operation Description:

Use this procedure to troubleshoot the electrical system if a problem is suspected with a sensor supply or if any one of the diagnostic codes in Table 1 is active or easily repeated.

Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
41-3 8 Volt DC Supply : Voltage Above Normal The digital sensor supply voltage is above normal. The code is logged.
All sensors are set to default values.
41-4 8 Volt DC Supply : Voltage Below Normal The digital sensor supply voltage is below normal.
232-3 5 Volt Sensor DC Power Supply : Voltage Above Normal The sensor supply voltage is above normal. The code is logged.
All sensors are set to default values.
232-4 5 Volt Sensor DC Power Supply : Voltage Below Normal The sensor supply voltage is below normal.
262-3 5 Volt Sensor DC Power Supply : Voltage Above Normal The sensor supply voltage is above normal. The code is logged.
All sensors are set to default values.
262-4 5 Volt Sensor DC Power Supply : Voltage Below Normal The sensor supply voltage is below normal.
263-3 Digital Sensor Power Supply (8V Or 12V) : Voltage Above Normal The digital sensor supply voltage is above normal. The code is logged.
All sensors are set to default values.
263-4 Digital Sensor Power Supply (8V Or 12V) : Voltage Below Normal The digital sensor supply voltage is below normal.

System Operation

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

 

  • Engine oil pressure
  • Atmospheric pressure
  • Fuel pressure
  • Turbocharger outlet pressure sensor
  • Engine coolant temperature
  • Inlet air temperature
  • Fuel temperature
  • Auxiliary pressure

The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the following sensors:

 

  • Coolant level sensor
  • Auxiliary temperature sensor

The supply voltage for the sensors is routed from the ECM to terminal A of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal B of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If any of the -3 diagnostic codes are active, it is possible that a sensor has been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has failed.

Test Step 1. Inspect Electrical Connectors and Wiring

 

  1. Remove electrical power from the ECM.


Illustration 2 g01430140
ECM
(1) J1/P1 connectors
(2) J2/P2 connectors

  1. 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 g01430145
P1 ECM connector
(P1-2) Coolant level
(P1-29) Digital return
(P1-30) Sensor return
(P1-35) + 8 V digital supply
(P1-36) + 5 V sensor supply


Illustration 4 g01430143
P2 ECM connector

(P2-36) + 5 V sensor supply

(P2-30) Sensor return

(P2-2) Inlet air temperature

(P2-23) Turbocharger outlet pressure

(P2-8) Engine oil pressure

(P2-20) Atmospheric pressure

(P2-9) Fuel pressure

(P2-14) Engine coolant temperature

(P2-3) Fuel temperature

(P2-24) Auxiliary temperature

(P2-15) Auxiliary pressure


Illustration 5 g01159881
Sensor connector

(A) +5 V or +8 V sensor supply

(B) Sensor return

(C) Signal

  1. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.

 

  1. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.

 

  1. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.

Expected Result:

All 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 – There is a problem with the connectors and/or wiring.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 for Active Diagnostic Codes

 

  1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

 

  1. Restore electrical power to the ECM.

 

  1. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Look for the following diagnostic codes: 
    • 232-3 
    • 232-4 
    • 41-3 
    • 41-4 
    • 262-3 
    • 262-4 
    • 263-3 
    • 263-4 

    Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

No diagnostic codes are active.

Results:

 

  • OK – No diagnostic code is active.Repair: The problem is no longer present. If the problem is intermittent, refer to Troubleshooting, “Electrical Connectors – Inspect”.

    STOP

     

  • Not OK – A +5 V diagnostic code is active at this time. Proceed to Test Step 3. 
  • Not OK – A +8 V diagnostic code is active at this time. Proceed to Test Step 5.

Test Step 3. Disconnect the 5 Volt Sensor(s) while you Monitor the Active Diagnostic Codes

 

  1. Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 Volt sensor at the sensor connector. Check for an active -3 code or an active -4 code.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

  1. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

 

  • OK – The diagnostic code deactivates when a particular sensor is disconnected.Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect the connector(s). Verify that the problem is resolved.

    STOP

     

  • Not OK – The diagnostic code remains active after a sensor is disconnected. Leave the sensor disconnected. The sensor is not the cause of the diagnostic code. Proceed to Test Step 4.

Test Step 4. Check the +5 V Supply Voltages at the ECM

 

  1. Disconnect the J1/P1 and the J2/P2 ECM connector.

 

  1. Fabricate jumper wires that are long enough to be used to measure the supply voltages at the ECM connector. Crimp connector sockets to one end of each jumper wire.

 

  1. Remove the wires from terminal locations P1-36 (+5 V sensor supply) and P1-30 (sensor return). Remove the wires from terminal locations P2-36 (+5 V sensor supply) and P2-30 (sensor return). Install a jumper wire into each of these terminal locations.

 

  1. Connect the J1/P1 and the J2/P2 ECM connector.

 

  1. Restore electrical power to the ECM.

 

  1. Measure the voltage between the jumper wire in P1-36 (+5 V sensor supply) and the jumper wire in P1-30 (sensor return).

 

  1. Measure the voltage between the jumper wire in P2-36 (+5 V sensor supply) and the jumper wire in P2-30 (sensor return).

 

  1. Remove electrical power from the ECM.

Expected Result:

The voltage measurement is 5.0 ± 0.2 VDC.

Results:

 

  • OK – The voltage measurement is 5.0 ± 0.2 VDC. The ECM is operating correctly.Repair: There is a problem with the harness. Repair the harness or replace the harness.

    STOP

     

  • Not OK – The voltage measurement is not 5.0 ± 0.2 VDC.Repair: Replace the ECM. Refer to Troubleshooting, “ECM – Replace”.

    STOP

Test Step 5. Disconnect the +8 V Sensors while you Monitor the Active Diagnostic Codes

 

  1. Monitor the active diagnostic code screen on Cat ET while you disconnect the +8 V sensors at the sensor connector. Check for an active -3 code or an active -4 code.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

  1. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when the sensor is disconnected.

Results:

 

  • OK – The +8 V diagnostic code deactivates when the sensor is disconnected.Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect all of the connectors. Verify that the problem is resolved.

    STOP

     

  • Not OK – The +8 V diagnostic code remains active after the sensor is disconnected. Leave the sensor disconnected. The sensor is not the cause of the diagnostic code. Proceed to Test Step 6.

Test Step 6. Check the +8 V Supply Voltage at the ECM

 

  1. Disconnect the J1/P1 ECM connector.

 

  1. Fabricate two jumper wires that are long enough to be used to measure the supply voltage at the ECM connectors. Crimp connector sockets to one end of each jumper wire.

 

  1. Remove the wires from terminal locations P1-35 (+8 V sensor supply) and P1-29 (sensor return). Install a jumper wire into each of these terminal locations.

 

  1. Connect the J1/P1 ECM connector.

 

  1. Restore electrical power to the ECM.

 

  1. Measure the voltage between the jumper wire in P1-35 (+8 V sensor supply) and P1-29 (sensor return).

 

  1. Remove electrical power from the ECM. Replace all wires and connectors to the original configuration.

Expected Result:

The voltage measurement is 8.0 ± 0.4 VDC.

Results:

 

  • OK – The voltage measurement is 8.0 ± 0.4 VDC. The ECM is operating correctly.Repair: There is a problem with the harness. Repair the harness or replace the harness.

    STOP

     

  • Not OK – The voltage measurement is not 8.0 ± 0.4 VDC.Repair: Replace the ECM. Refer to Troubleshooting, “ECM – Replace”.

    STOP

 

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