G3500 A3 Engines Caterpillar

Use this procedure to troubleshoot the following diagnostic codes:

• 262-3 5 Volt Sensor DC Power Supply : Voltage Above Normal

• 262-4 5 Volt Sensor DC Power Supply : Voltage Below Normal

The Electronic Control Module (ECM) supplies 5.0 ± 0.5 VDC to the following components:

• Inlet air temperature sensor

• Engine oil temperature sensor

• Unfiltered engine oil pressure sensor

• Filtered engine oil pressure sensor

• Desired speed potentiometer (if equipped)

For the sensor circuits, a 262-3 diagnostic code is probably caused by a short circuit to a higher voltage source in the harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

For the desired speed potentiometer circuit, a 262-3 diagnostic code will be activated if either of these conditions occur:

• A short in the wiring for the desired speed signal to a voltage that is greater than +5 VDC

• Adjustment of the desired speed potentiometer near the maximum desired speed

For the sensor circuits, a 262-4 code is probably caused by a short circuit to ground in the engine harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

For the desired speed potentiometer circuit, a 262-4 diagnostic code will be activated if either of these conditions occur:

• A short in the wiring for the desired speed signal to ground

• Adjustment of the desired speed potentiometer near the minimum desired speed

This troubleshooting procedure may generate additional diagnostic codes. Continue to troubleshoot the cause of the original diagnostic code before troubleshooting other codes. Clear the diagnostic codes after the problem is resolved.

A 262-4 diagnostic code will be activated if both of these conditions occur:

Illustration 1	g02338548
Schematic for the 5 V supply

Test Step 1. Inspect the Electrical Connectors and the Wiring

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

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

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   Illustration 2	g01250263
   Top view of the front of the engine (1) Inlet air temperature sensor (2) Pressure sensor for unfiltered oil (3) Pressure sensor for filtered oil (4) Oil temperature sensor

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   Illustration 3	g02339137
   Typical location of the desired speed potentiometer (typical display panel)

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   Illustration 4	g01393788
   Location of the ECM connectors for the 5 V supply(typical left front engine view) (5) J1/P1 ECM connectors

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   Illustration 5	g01393791
   Location of connectors for the 5 V supply(typical left rear engine view) (6) Engine interface connector

2. Thoroughly inspect the connectors for sensors (1), (2), (3), and (4). Also, thoroughly inspect the connector for the desired speed potentiometer, ECM connectors (5), and engine interface connector (6).

3. Check the allen head screws for each of the ECM connectors and the engine interface connector for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque value.
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   Illustration 6	g01393742
   Terminal locations at the P1 ECM connector for the sensor supply circuit (P1-2) 5 V supply (P1-3) Return (P1-18) 5 V supply (P1-35) Return

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   Illustration 7	g01393743
   Terminal locations at the engine interface connector for the sensor supply circuit (Terminal 6) 5 V supply (Terminal 8) Return

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   Illustration 8	g01159881
   Terminal locations at the sensor connector for the sensor supply circuit (Terminal A) 5 V supply (Terminal B) Return (Terminal C) Signal

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   Illustration 9	g02337298
   Terminal locations at the desired speed potentiometer (Terminal 1) Return/shield (Terminal 2) Signal (Terminal 3) +5 V supply

4. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuits for the 5 V supply.

5. Check the harness and wiring for abrasion and for pinch points from each 5 V component 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, or sockets are not connected properly. At least one of the connectors and the wiring has corrosion, abrasion, and/or pinch points.

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

  STOP

Test Step 2. Use Cat ET to Identify the Active Diagnostic Code

1. Establish communication between Cat ET and the engine ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.

2. Rotate the engine speed dial (if equipped) to a midpoint speed position between the minimum and the maximum settings.

3. Place the Engine Control Switch (ECS) in the STOP/COOLDOWN position.

4. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 30 seconds so that any codes may become activated. Look for these codes:

   • 262-3 5 Volt Sensor DC Power Supply voltage above normal

   • 262-4 5 Volt Sensor DC Power Supply voltage below normal

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

Expected Result:

The 262-3 code or the 262-4 code is not active or logged.

Results:

• No codes - There are no active codes or logged codes. If the engine is equipped with a desired speed potentiometer, proceed to Test Step 3. Otherwise, the initial diagnostic code was probably caused by a poor electrical connection. Resume normal operation. STOP.

• Active code - The 262-3 code or the 262-4 code is active. Proceed to Test Step 4.

• Logged code - The 262-3 code or the 262-4 code is not active. However, there is at least one logged code for the +5 V 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. Check for a Short in the Harness for the "DESIRED SPEED" Potentiometer

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

2. Label the wiring that is connected to the "DESIRED SPEED" potentiometer. Disconnect the wiring from the "DESIRED SPEED" potentiometer.

3. Disconnect the P1 connector.

4. Measure the resistance between terminal P1-16 and all of the other terminals on the P1 connector.

5. Restore the wiring to the original configuration.

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

• OK - Each check of the resistance indicates an open circuit. The wiring for the "DESIRED SPEED" potentiometer appears to be OK.

  Repair: The "DESIRED SPEED" potentiometer may have an internal short circuit. Perform the following procedure:

  1. Check the "DESIRED SPEED" potentiometer in order to ensure that the potentiometer does not have an internal short circuit. Replace the "DESIRED SPEED" potentiometer, if necessary. Continue with this procedure when the "DESIRED SPEED" potentiometer is operating correctly.

  2. Connect the wiring to the "DESIRED SPEED" potentiometer. Be sure to connect each wire to the appropriate terminal.

  3. Connect the P1 connector to the ECM.

  4. Verify that the original problem is resolved.

  STOP

• Not OK - At least one check of the resistance indicates a short circuit. There is a problem with the wiring for the "DESIRED SPEED" potentiometer.

  Repair: Perform any necessary repairs or replace parts, if necessary.

  STOP

Test Step 4. Isolate the Analog Supply Circuits to Check the ECM for a Problem

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

2. Remove the wires from terminal 2 and terminal 18 from the P1 connector.

3. Set the engine control to the STOP position.

4. Use Cat ET to look for diagnostic codes.

Expected Result:

No active codes

Results:

• OK - No codes - The 262-3 code or the 262-4 code is not active. Disconnecting all of the 5 V wiring from the ECM eliminated the active "5 Volt Sensor Supply" diagnostic code. There is a problem with a connector and/or the wiring in a harness. Proceed to Test Step 5.

• Not OK - Active code - The 262-3 code or the 262-4 code is active. Disconnecting all of the 5 V wiring from the ECM did not eliminate the +5 V diagnostic code.

  Repair: There may be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance.

  STOP

Test Step 5. Check for a Problem in the Analog Speed Circuit

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

2. Insert the wire for terminal 18 into the P1 connector. Pull on the wire in order to verify that the terminal is fully inserted into the connector.

3. Rotate the "DESIRED SPEED" potentiometer clockwise to the maximum speed position.

4. Set the engine control to the STOP position.

5. Use Cat ET to look for diagnostic codes.

Expected Result:

No active codes

Results:

• OK - No codes - The 262-3 code or the 262-4 code is not active. Connecting the wiring for the analog speed circuit to the ECM did not cause a diagnostic code. The wiring for the analog speed circuit appears to be OK. Proceed to Test Step 6.

• Not OK - Active codes - The 262-3 code or the 262-4 code is active. Connecting the wiring for the analog speed circuit to the ECM caused a diagnostic code. Proceed to Test Step 8.

Test Step 6. Check for a Problem in the Analog Sensor Circuits

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

2. Insert terminal 2 into the P1 connector. Pull on the wire in order to verify that the terminal is fully inserted into the connector.

3. Set the engine control to the STOP position.

4. Use Cat ET to look for diagnostic codes.

Expected Result:

No active codes

Results:

• OK - No codes - The 262-3 code or the 262-4 code is not active. Connecting the 5 VDC for the sensors did not cause a diagnostic code. The problem appears to be resolved.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection. Return the engine to service.

  STOP

• Not OK - Active code - The 262-3 code or the 262-4 code is active. Connecting the 5 VDC for the sensors caused a diagnostic code. Proceed to Test Step 7.

Test Step 7. Disconnect the Individual Analog Sensors and Check for Active Diagnostic Codes.

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

2. Disconnect the following sensors:

   • Inlet air temperature

   • Engine oil temperature

   • Unfiltered engine oil pressure

   • Filtered engine oil pressure

3. Set the engine control to the STOP position.

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

4. Observe the "Active Diagnostic" screen on Cat ET. Verify that the 262-3 code or the 262-4 code is not active.

5. Connect the sensors one at a time. After you connect a sensor, wait for at least 30 seconds and then observe the "Active Diagnostic" screen on Cat ET.

Expected Result:

A "5 Volt Sensor" diagnostic code is activated when a particular sensor is connected.

Results:

• OK - A "5 Volt Sensor" diagnostic code is activated when a particular sensor is connected. The sensor and/or the wiring for the sensor has a short circuit.

  Repair: Perform the following procedure:

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

  2. Disconnect the suspect sensor.

  3. Set the engine control to the STOP position. Use Cat ET to clear the logged 262-3 or 262-4 code.

  4. Connect the suspect sensor. Verify that the diagnostic code recurs.

     If these conditions are true, replace the sensor.

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

  STOP

• Not OK - A "5 Volt Sensor" diagnostic code is still active while all of the 5 V sensors are disconnected. Do not connect the sensors. Proceed to Test Step 8.

Test Step 8. Use a Multimeter to Locate the Problem in the Harness

1. Insert 7X-1710 Multimeter Probes beside terminals P1-2 and P1-3. Measure the voltage across the probes.

   Note: The voltage reading will depend on the problem with the wiring. The voltage reading will be low or high.

2. Carefully wiggle the wiring in the engine harness while you monitor the voltage indication on the multimeter. Look for a voltage of approximately 5 VDC. Be sure to wiggle the wiring near each of the connectors that are associated with the 5 V supply.

Expected Result:

The voltage reading changes to approximately 5 VDC when the wiring is wiggled at a particular location.

Results:

• OK - The voltage reading changes to approximately 5 VDC when the wiring is wiggled at a particular location.

  Repair: Identify the problem with the harness. Repair the harness, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP