G3516B Engines Caterpillar

The Electronic Control Module (ECM) supplies 8.0 ± 0.8 VDC to these sensors:

• Sensor for engine coolant pressure (outlet)

• Sensor for inlet air pressure

• Sensor for atmospheric pressure (if equipped)

• All of the detonation sensors

A "+8 V sensor supply" diagnostic code is probably caused by a short circuit or an open circuit in a 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 codes after the problem is resolved.

Illustration 1	g01071121
Schematic for the 8 volt supply

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 2	g01071133
Terminal box (1) J2/P2 connectors for the ECM (2) J1/P1 connectors for the ECM (3) J12/P12 connectors for the harness from the sensors (4) J11/P11 connectors for the harness from the detonation sensors (5) 16 amp circuit breaker

1. Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (5) to the OFF position.

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

2. Thoroughly inspect each of the following connectors:

   • J1/P1 and J2/P2 connectors

   • J11/P11 and 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	g01071138
      Harness side of the P1 connector (P1-4) 8 volt supply (P1-5) Return

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      Illustration 4	g01071141
      Harness side of the P2 connector (P2-54) Return (P2-55) Return (P2-56) 8 volt supply (P2-57) 8 volt supply

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      Illustration 5	g00888905
      Harness side of the P11 connector (P11-A) Return (P11-E) Return (P11-F) 8 volt supply (P11-J) 8 volt supply

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      Illustration 6	g01076901
      Harness side of the P12 connector (P12-L) 8 volt supply (P12-N) Return

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the 8 volt supply.
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      Illustration 7	g01071162
      Left side view (6) Sensor for engine coolant pressure (outlet) (7) Detonation sensor (8) Sensor for inlet air pressure

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      Illustration 8	g01071169
      Left side views of a 50 Hz engine and a 60 Hz engine (9) Sensor for atmospheric pressure (if equipped)

   3. Check the harness and wiring for abrasion and for pinch points from each 8 volt sensor 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 sockets are not connected properly. At least one of the connectors and/or the wiring has 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

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. Wait at least 30 seconds so that any codes may become activated. Look for these codes:

   • 41-03 8 Volt DC Supply short to +batt

   • 41-04 8 Volt DC Supply short to ground

4. Observe the "Logged Diagnostic" screen on Cat ET. Look for the same codes.

Expected Result:

The 41-03 code or the 41-04 code is not active.

Results:

• No codes - The 41-03 code or the 41-04 code is not active. The +8 volt sensor supply is operating correctly at this time.

  STOP

• Active code - The 41-03 code or the 41-04 code is active. Proceed to Test Step 3.

• Logged code - The 41-03 code or the 41-04 code is not active. However, there is at least one logged code for the 8 volt sensor supply.

  Repair: There may be a problem with the wiring and/or a connector. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  Verify that the wiring and/or connectors are OK. Check for diagnostic codes again. Proceed to Test Step 3, if necessary.

Test Step 3. Disconnect the 8 Volt Sensors and Look for Active Diagnostic Codes

1. Turn on the "Active Diagnostic" screen on Cat ET. Verify that the "41-03" or "41-04" code is active.

2. Disconnect each 8 volt sensor one at a time. After you disconnect each sensor, wait for at least 30 seconds and then observe the "Active Diagnostic" screen on Cat ET.

   Note: An "Open Circuit" code will be generated for each sensor that is disconnected. This is normal. Clear the codes after you complete this procedure.

Expected Result:

The original "8 Volt DC Supply" diagnostic code is deactivated when a particular sensor is disconnected.

Results:

• Yes - The original "8 Volt DC Supply" diagnostic code is deactivated when a particular sensor is disconnected. The sensor and/or the wiring for the sensor has a short circuit.

  Repair: Perform the following procedure:

  1. Reconnect the suspect sensor. Verify that the diagnostic code recurs.

  2. Disconnect the suspect sensor. Verify that the diagnostic code is deactivated.

     If these conditions are true, repair the sensor or the sensor's harness. Replace parts, if necessary.

  3. Clear all of the diagnostic codes. Verify that the problem is resolved.

  STOP

• No - The original "8 Volt DC Supply" diagnostic code is still active when a particular sensor is disconnected. Do not reconnect the sensors. Proceed to Test Step 4.

Test Step 4. Isolate the Wiring Harnesses from 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	g01076916
   Harness side of ECM P1 connector and P2 connector (P1-4) 8 volt supply for the pressure sensors (P2-56) 8 volt supply for the detonation sensors (P2-57) 8 volt supply for the detonation sensors

2. Use a 151-6320 Wire Removal Tool to remove the wires from the following terminals:

   • Terminal P1-4

   • Terminals P2-56 and P2-57

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

4. Wait for at least 30 seconds and then observe the "Active Diagnostics" screen on Cat ET. Determine if a 41-03 code or a 41-04 code is active.

Expected Result:

No active codes

Results:

• No codes - The 41-03 code or the 41-04 code is not active. Disconnecting all of the 8 volt wiring from the ECM eliminated the active "8 Volt DC Supply" diagnostic code. There is a problem in a connector and/or the wiring in a harness. Proceed to Test Step 5.

• Active code - There is an active 41-03 or 41-04 code. Disconnecting all of the 8 volt wiring from the ECM did not eliminate the active "8 Volt DC Supply" diagnostic code. There may be a problem with the ECM.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this 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 original ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

Test Step 5. Check the Wiring Harness Inside the Terminal Box

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

2. Insert terminals 56 and 57 into the P2 connector. Insert terminal 4 into the P1 connector. Pull on the wires in order to verify that the terminals are fully inserted into the connectors.

3. Disconnect the following connectors:

   • P1 and P2

   • P11 and P12

   This will isolate the 8 volt wiring inside the terminal box.

   Note: During each of the following measurements, wiggle the wires inside the terminal box in order to check for an intermittent problem. Be sure to wiggle the wires near each of the connectors.

4. Measure the resistance between terminal P1-4 and all of the other terminals on the P1 connector.

5. Measure the resistance between terminal P2-56 and all of the other terminals on the P2 connector.

6. Measure the resistance between terminal P2-57 and all of the other terminals on the P2 connector.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

• OK - Each check of the resistance is greater than 20,000 Ohms. The 8 volt wires and connectors in the terminal box do not have a short circuit. Proceed to Test Step 6.

• Not OK - At least one check of the resistance is less than 20,000 Ohms. There is a problem with the wiring inside the terminal box.

  Repair: Repair the terminal box's harness, when possible. Replace parts, if necessary.

  STOP

Test Step 6. Check the Harness for the Detonation Sensors

1. Verify that all of the detonation sensors are disconnected.

   Note: During each of the following measurements, wiggle the wires inside the terminal box in order to check for an intermittent problem. Be sure to wiggle the wires near each of the connectors.

2. Measure the resistance between terminal P11-F and all of the other terminals on the P11 connector.

3. Measure the resistance between terminal P11-J and all of the other terminals on the P11 connector.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

• OK - Each check of the resistance is greater than 20,000 Ohms. The harness for the detonation sensors appears to be OK. Proceed to Test Step 7.

• Not OK - At least one check of the resistance is less than 20,000 Ohms. There is a problem with a connector and/or at least one of the 8 volt wires in the harness for the detonation sensors.

  Repair: Repair the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 7. Check the Harness for the Sensors

1. Verify that the sensors for the following parameters are disconnected:

   • Engine coolant pressure

   • Inlet air pressure

   • Atmospheric pressure

   Note: During each of the following measurements, wiggle the wires inside the terminal box in order to check for an intermittent problem. Be sure to wiggle the wires near each of the connectors.

2. Measure the resistance between terminal P12-L and all of the other terminals on the P12 connector.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

• OK - Each check of the resistance is greater than 20,000 Ohms. The problem seems to be resolved. The initial diagnostic code was probably caused by a poor electrical connection.

  Repair: Reconnect all of the connectors and resume normal operation.

  STOP

• Not OK - At least one check of the resistance is less than 20,000 Ohms. There is a problem with a connector and/or the 8 volt wires in the harness for the sensors.

  Repair: Repair the harness, when possible. Replace parts, if necessary.

  STOP