G3516B Engines Caterpillar

Use this procedure to troubleshoot diagnostic codes for open circuits or short circuits for the sensors of these parameters:

• Engine coolant temperature

• Inlet air temperature

• Engine oil temperature

• Filtered engine oil pressure

• Unfiltered engine oil pressure

Note: The engine coolant temperature sensor does not require +5 VDC from the Electronic Control Module (ECM). The engine coolant temperature sensor is a passive sensor of the analog type. The sensor operates without a voltage supply from the ECM.

The ECM can be configured for one of these types of speed control:

• Potentiometer

• 4-20 ma

The "DESIRED SPEED" potentiometer (if equipped) must be supplied with +5 VDC from the ECM. If the "DESIRED SPEED" potentiometer has a short circuit or the potentiometer's wiring has a short circuit, a 262-03 or 262-04 diagnostic code may be activated. There are no diagnostic codes for the circuit of the "DESIRED SPEED" potentiometer.

An -03 code is probably caused by a problem in an engine harness. There may be an open circuit in a harness, or a short circuit to a positive voltage source in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

An -04 code is probably caused by a short circuit to ground in an engine harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

Logged diagnostic codes provide an historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.

This troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic code after the problem is resolved.

Illustration 1	g01078407
Schematic for the analog sensors

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 2	g01071294
Terminal box (1) ECM connectors J1/P1 (2) J12/P12 connectors for the analog sensors (3) 16 amp circuit breaker

1. Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (3) to the OFF position.

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

2. Thoroughly inspect the following connectors:
   • J1/P1 connectors

   • J12/P12 connectors on the terminal box

   1. Check the torque of the allen head screw for the ECM connector. The proper torque is 6 ± 1 N·m (55 ± 9 lb in).
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   Illustration 3	g01071300
   Harness side of the P1 connector (P1-2) 5 volt supply (P1-3) Return (P1-14) Signal for the inlet manifold air temperature (P1-17) Signal for the engine oil temperature (P1-24) Signal for the filtered engine oil pressure (P1-26) Signal for the unfiltered engine oil pressure (P1-27) Signal for the engine coolant temperature

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   Illustration 4	g00889763
   Harness side of the P12 connector (P12-A) 5 volt supply (P12-C) Return (P12-E) Signal for the unfiltered engine oil pressure (P12-F) Signal for the filtered engine oil pressure (P12-H) Signal for the engine oil temperature (P12-J) Signal for the engine coolant temperature (P12-K) Signal for the inlet manifold air temperature

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the analog sensors.
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   Illustration 5	g01071307
   Right side view (4) Inlet air temperature sensor (5) Engine coolant temperature sensor

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   Illustration 6	g01071314
   Left side view (6) Unfiltered oil pressure sensor (7) Filtered oil pressure sensor (8) Oil temperature sensor

   3. Check the harness and wiring for abrasion and pinch points from the analog sensors to the ECM.

Expected Result:

All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points. The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - At least one of the connectors, pins, and/or sockets are not connected properly. At least one of the connectors and/or the wiring have corrosion, abrasion, and/or pinch points.

  Repair: Perform the necessary repairs and/or replace parts, if necessary.

  STOP

Test Step 2. Check for Diagnostic Codes for the Power Supply

1. Connect Cat ET to the service tool connector on the terminal box.

2. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

3. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate. Look for these codes:
   • 262-03 5 Volt Sensor DC Power Supply short to +batt

   • 262-04 5 Volt Sensor DC Power Supply short to ground

Expected Result:

There are no active "5 Volt Sensor DC Power Supply" diagnostic codes.

Results:

• No codes - There are no active "5 Volt Sensor DC Power Supply" diagnostic codes. Proceed to Test Step 3.

• Active code - There is an active "5 Volt Sensor DC Power Supply" diagnostic code. This procedure will not work when this type of code is active.

  Repair: Refer to Troubleshooting, "+5V Sensor Supply".If necessary, return to this functional test in order to troubleshoot the analog sensor after the "+5 V Sensor Supply" diagnostic code has been resolved.

  STOP

Test Step 3. Check for Active Analog Sensor Diagnostic Codes

1. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 30 seconds so that any codes may become activated. Look for the codes that are listed in Table 1:
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   Table 1

   Analog Sensor Diagnostic Codes
   100-03	Engine Oil Pressure open/short to +batt
   100-04	Engine Oil Pressure short to ground
   110-03	Engine Coolant Temperature open/short to +batt
   110-04	Engine Coolant Temperature short to ground
   172-03	Intake Manifold Air Temp open/short to +batt
   172-04	Intake Manifold Air Temp short to ground
   175-03	Engine Oil Temperature open/short to +batt
   175-04	Engine Oil Temperature short to ground
   542-03	Unfiltered Engine Oil Pressure open/short to +batt
   542-04	Unfiltered Engine Oil Pressure short to ground

2. If one of the above codes is active, identify the type of diagnostic according to the condition: the diagnostic code is either "open/short to +batt" (FMI 03) or "short to ground" (FMI 04).

Expected Result:

None of the above codes are active.

Results:

• No active codes - None of the above codes are active.

  Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".If the engine is running properly at this time, there may be an intermittent problem in the harness that is causing the codes to be logged. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Active "open/short to +batt" (FMI 03) - There is an active "open/short to +batt" diagnostic code. If you are troubleshooting the sensor for engine coolant temperature, proceed to Test Step 6. Otherwise, proceed to Test Step 5.

• Active "short to ground" (FMI 04) - There is an active "short to ground" diagnostic code. Proceed to Test Step 4.

Test Step 4. Create an Open Circuit for the Sensor

1. Set the engine control to the OFF/RESET mode.

2. Disconnect the sensor that has the "short to ground" diagnostic code.

3. Set the engine control to the STOP mode.

4. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate. Look for an active "open/short to +batt" diagnostic code.

Expected Result:

There is an active "open/short to +batt" diagnostic code for the disconnected sensor.

Results:

• Yes - Before the suspect sensor was disconnected, there was an active "short to ground" diagnostic code for the sensor. After the suspect sensor was disconnected, there was an active "open/short to +batt" diagnostic code for the sensor.

  Repair: Reconnect the sensor. If the active "short to ground" diagnostic code recurs, replace the original sensor.Verify that the code does not activate when the new sensor is installed. Clear the logged diagnostic code from the ECM.

  STOP

• No - Before the suspect sensor was disconnected, there was an active "short to ground" diagnostic code for the sensor. After the suspect sensor was disconnected, the active "open/short to +batt" diagnostic code remained. If you are troubleshooting the sensor for engine coolant temperature, proceed to Test Step 6. Otherwise, proceed to Test Step 5.

Test Step 5. Check the Supply Voltage at the Sensor Connector

1. Verify that the suspect sensor is disconnected from the engine harness.

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Illustration 7	g00889729
Harness connectors for the various sensors (A) 5 volt supply (B) Return (C) Signal

2. At the harness connector for the suspect sensor, measure the voltage between terminal A and terminal B.

Expected Result:

The voltage between terminal A and terminal B is +5.0 ± 0.5 VDC.

Results:

• OK - The voltage between terminal A and terminal B is +5.0 ± 0.5 VDC. +5 V is present at the sensor connector. Proceed to Test Step 6.

• Not OK - The voltage between terminal "B" and terminal "C" is not +5.0 ± 0.5 VDC. The 5 volt supply is not present at the sensor connector. 5 volts must be present at the sensor in order to continue this procedure. The 5 volt wiring problem may be inside the terminal box, or in the engine harness.

  Repair: Verify that the wiring and/or connectors are OK. Repair any faulty wiring and/or connectors, when possible. Replace any faulty wiring and/or connectors, if necessary. Refer to Troubleshooting, "Inspecting Electrical Connectors". Check for diagnostic codes again.

  STOP

Test Step 6. Check the Pull-Up Voltage at the Sensor

1. Verify that the suspect sensor's connector is disconnected from the engine harness.

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Illustration 8	g00889801
Harness connectors for the various sensors (A) 5 volt supply (B) Return (C) Signal (1) Signal (2) Return

2. At the harness connector for the suspect sensor, measure the voltage between terminal B and terminal C, or between terminal 1 and terminal 2.

Expected Result:

Pull-up voltage is present between the signal terminal and the return terminal.

Results:

• OK - Pull-up voltage is present between the signal terminal and the return terminal. The pull-up voltage that is created by the ECM is present at the sensor connector. The signal wire and the return wire for the suspect sensor appear to be OK. Proceed to Test Step 8.

• Not OK - Pull-up voltage is not present between the signal terminal and the return terminal. The pull-up voltage that is created by the ECM is not present at the sensor connector. Proceed to Test Step 7.

Test Step 7. Check the Pull-Up Voltage at the ECM

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

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Illustration 9	g01076932
Harness side of the P1 connector (P1-3) Analog return (P1-14) Inlet air temperature (P1-17) Oil temperature (P1-24) Filtered oil pressure (P1-26) Unfiltered oil pressure (P1-27) Engine coolant temperature

2. Use a 151-6320 Wire Removal Tool to remove the signal wire for the suspect sensor from the P1 connector.

3. Use a jumper wire with Deutsch terminals on the ends. Insert one end of the jumper wire into the open terminal of the P1 connector.

4. Connect a multimeter lead to the end of the jumper wire that is not inserted into the connector.

5. At the harness side of the P1 connector, insert a 7X-1710 Multimeter Probe along terminal 3.

6. Connect the other multimeter lead to the probe.

7. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

8. Measure the pull-up voltage at the ECM.

Expected Result:

Pull-up voltage for the suspect sensor at the ECM is present.

Results:

• OK - Pull-up voltage for the suspect sensor at the ECM is present. The ECM is producing a pull-up voltage that is valid. There is a problem with the signal wire between P1 and the harness connector for the sensor. There may be a problem with a connector.

  Repair: Perform the following procedure:Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.Disconnect the multimeter leads.Use a 151-6320 Wire Removal Tool to remove the jumper wire from the P1 connector.Reinstall the terminal that was removed from the P1 connector. Pull on the wire in order to verify proper installation of the terminal.Verify that the wiring and/or connectors are OK. Repair any faulty wiring and/or connectors, when possible. Replace any wiring and/or connectors, if necessary. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - Pull-up voltage for the suspect sensor at the ECM is not present. Proceed to Test Step 9.

Test Step 8. Check the Sensor

1. Temporarily connect a sensor that is known to be good to the engine harness.

2. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

3. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.

Expected Result:

No diagnostic codes are activated.

Results:

• OK - No diagnostic codes are activated when a good sensor is temporarily installed. Connecting a new sensor resolved the problem.

  Repair: Perform the following procedure:

  1. Reconnect the suspect sensor. Verify that the "open/short to +batt" diagnostic code recurs.

  2. Disconnect the suspect sensor. Verify that the "open/short to +batt" diagnostic code is deactivated.

  3. Connect the new connector. Verify that no diagnostic codes are activated.

     If these conditions are true, replace the faulty sensor with the new sensor. For the proper torque value for the new sensor, refer to the Specifications manual.

  4. Clear all of the diagnostic codes. Verify that the problem has been resolved.

  STOP

• Not OK - The active "open/short to +batt" code remains. Connecting a new sensor did not resolve the problem. Proceed to Test Step 9.

Test Step 9. Check the Operation of the ECM

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Illustration 10	g01076937
Harness side of the P1 connector (P1-3) Analog return (P1-14) Inlet manifold air temperature (P1-17) Oil temperature (P1-19) Unused ground for the ECM (P1-24) Filtered oil pressure (P1-26) Unfiltered oil pressure (P1-27) Engine coolant temperature

1. Verify that the signal wire for the suspect sensor has been removed from the P1 connector.

2. Clear any existing diagnostic codes.

3. Observe the "Active Diagnostic" screen on ET. Allow a minimum of 30 seconds for any codes to activate.

   An active "open/short to +batt" diagnostic code is generated for the sensor.

4. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

5. Use a jumper wire that is the appropriate length with Deutsch terminals on the ends. Install one end of the jumper wire into the terminal for the signal wire that was removed from the P1 connector. Install the other end of the jumper wire into terminal P1-19. This will replace the sensor circuit with a short circuit.

6. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

7. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.

   An active "short to ground" diagnostic code is generated.

Expected Result:

Active "open/short to +batt" and "short to ground" diagnostic codes are generated according to the above steps.

Results:

• OK - Active "open/short to +batt" and "short to ground" diagnostic codes are generated according to the above steps. The ECM is operating correctly. The initial diagnostic code was probably caused by a poor electrical connection.

  Repair: Perform the following procedure:Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.Use a 151-6320 Wire Removal Tool to remove the jumper wire from the P1 connector.Reinstall the terminal that was removed from the P1 connector. Pull on the wire in order to verify proper installation of the terminal.Resume normal operation.

  STOP

• Not OK - No active "open/short to +batt" and "short to ground" diagnostic codes were generated. The ECM is not operating correctly.

  Repair: It is unlikely that the ECM has failed. Perform this entire procedure again. If the problem is not resolved, perform the following steps:Temporarily install a new ECM. Refer to Troubleshooting, "Replacing the ECM".If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP