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.
| 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 for one second. | 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 for one second. | |
| 262-3 5 Volt Sensor DC Power Supply voltage above normal | The analog sensor supply voltage is above normal for one second. | The code is logged. All sensors are set to default values. |
| 262-4 5 Volt Sensor DC Power Supply voltage below normal | The analog sensor supply voltage is below normal for one second. | |
| 269-3 Sensor Power Supply voltage above normal | The analog sensor supply voltage is above normal for one second. | The code is logged. All sensors are set to default values. |
| 269-4 Sensor Power Supply voltage below normal | The analog sensor supply voltage is below normal for one second. | |
Note: The 262 diagnostic codes indicate a problem with the 5 V power supply on the J2 ECM connector. The 269 diagnostic codes indicate a problem with the 5 V power supply on the J1 ECM connector.
System Operation
The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:
- Atmospheric pressure sensor
- Engine oil pressure sensor
- Fuel pressure sensors
- Intake manifold pressure sensor
- Left track accumulator pressure sensor
- Right track accumulator pressure sensor
The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the following sensors:
- Accelerator throttle position sensor
- Decelerator throttle position 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.
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| Illustration 1 | g01382442 |
Schematic for the sensor supply circuits | |
Test Step 1. Inspect the Electrical Connectors and the Wiring
- Remove electrical power from the ECM.
- Thoroughly inspect the connectors for sensors (1), (2), (3), and (4). Also, thoroughly inspect ECM connectors (5) and (6). Inspect all of the connectors that are associated with each of the circuits.
Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
 | |
| Illustration 2 | g01381901 |
Locations of the components for the active analog sensors (typical left side engine view) (1) Intake manifold pressure sensor (2) Fuel pressure sensor (3) Atmospheric pressure sensor (4) Engine oil pressure sensor (5) J2/P2 ECM connectors (6) J1 ECM connector | |
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
 | |
| Illustration 3 | g01382455 |
Terminal locations at the P1 ECM connector for the sensor supply circuit (P1-2) Analog sensor supply (P1-3) Analog return (P1-4) Digital sensor supply (P1-18) Digital return | |
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| Illustration 4 | g01382480 |
Terminal locations at the P2 ECM connector for the sensor supply circuit (P2-17) Analog return (P2-72) Analog sensor supply | |
 | |
| Illustration 5 | g01159881 |
Terminal locations at the sensor connector for the sensor supply circuit (Terminal A) Sensor supply (Terminal B) Sensor return (Terminal C) Sensor signal | |
- Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- 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
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Restore electrical power to the ECM.
- Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Look for the following diagnostic codes:
- 41-3
- 41-4
- 262-3
- 262-4
- 269-3
- 269-4
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- 41-3
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 262-3, 262-4, 269-3 or 269-4 diagnostic code is active at this time. Proceed to Test Step 3.
- Not OK - A 41-3 or 41-4 diagnostic code is active at this time. Proceed to Test Step 5.
Test Step 3. Disconnect the Analog Sensors while you Monitor the Active Diagnostic Codes
- Use this procedure for any 262 diagnostic codes.
- Monitor the active diagnostic code screen on Cat ET while you disconnect each analog sensor at the sensor connector. Check for an active 262-3 code or an active 262-4 code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Disconnect the following sensors one at a time:
- Atmospheric pressure sensor
- Engine oil pressure sensor
- Fuel pressure sensor
- Intake manifold pressure sensor
- Atmospheric pressure sensor
- Monitor the active diagnostic code screen on Cat ET while you disconnect each analog sensor at the sensor connector. Check for an active 262-3 code or an active 262-4 code.
- Use this procedure for any 269 diagnostic codes.
- Monitor the active diagnostic code screen on Cat ET while you disconnect each analog sensor at the sensor connector. Check for an active 269-3 code or an active 269-4 code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Disconnect the following sensors one at a time:
- Fuel pressure sensor
- Left track accumulator pressure sensor
- Right track accumulator pressure sensor
- Fuel pressure sensor
- Monitor the active diagnostic code screen on Cat ET while you disconnect each analog sensor at the sensor connector. Check for an active 269-3 code or an active 269-4 code.
- 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 the sensor(s) is disconnected. Leave the sensor(s) disconnected. The sensor(s) is not the cause of the diagnostic code. Proceed to Test Step 4.
Test Step 4. Check the Supply Voltages for the Analog Sensors at the ECM
- Use this procedure for any 262 diagnostic codes.
- Disconnect the J2/P2 ECM connector.
- Fabricate two jumper wires that are long enough to be used to create a test circuit at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.
- Remove the wires from terminal locations P2-72 (analog sensor supply) and P2-17 (analog return). Install a jumper wire into each of these terminal locations.
- Connect the J2/P2 ECM connector.
- Restore electrical power to the engine ECM.
- Measure the voltage between the jumper wires that are in terminal locations P2-72 (analog sensor supply) and P1-17 (analog return).
- Remove electrical power from the ECM.
- Use this procedure for any 269 diagnostic codes.
- Disconnect the J1/P1 ECM connector.
- Fabricate two jumper wires that are long enough to be used to create a test circuit at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.
- Remove the wires from terminal locations P1-4 (analog sensor supply) and P1-18 (analog return). Install a jumper wire into each of these terminal locations.
- Connect the J1/P1 ECM connector.
- Restore electrical power to the engine ECM.
- Measure the voltage between the jumper wires that are in terminal locations P1-4 (analog sensor supply) and P1-18 (analog return).
- Remove electrical power from the ECM.
Expected Result:
Each 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: The supply wire is shorted to another wire in the harness or the supply wire is shorted to engine ground. Repair the supply wire. Verify that the problem is resolved.
STOP
- Not OK - The voltage measurement is not 5.0 ± 0.2 VDC.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.
STOP
Test Step 5. Disconnect the Digital Sensors while you Monitor the Active Diagnostic Codes
- Monitor the active diagnostic code screen on Cat ET while you disconnect the accelerator throttle position sensor and the decelerator throttle position sensor at the sensor connectors. Check for an active 41-3 code or an active 41-4 code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Remove electrical power from the ECM.
Expected Result:
The diagnostic code deactivates when one of the throttle position sensors is disconnected.
Results:
- OK - The 41-3 or 41-4 diagnostic code deactivates when one of the throttle position sensors 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 41-3 or 41-4 diagnostic code remains active after each of the throttle position sensors is disconnected. Leave the suspect sensor disconnected. The sensor is not the cause of the diagnostic code. Proceed to Test Step 6.
Test Step 6. Check the Digital Supply Voltage at the ECM
- Disconnect the J1/P1 ECM connector.
- Fabricate two jumper wires that are long enough to be used as a test circuit at the ECM connectors. Crimp connector sockets to one end of each of the jumper wires.
- Remove the wires from terminal locations P1-4 (digital sensor supply) and P1-18 (digital return). Install a jumper wire into each of these terminal locations.
- Connect the J1/P1 ECM connector.
- Restore electrical power to the engine ECM.
- Measure the voltage between the jumper wires that are in terminal locations P1-4 (digital sensor supply) and P1-18 (digital return).
- 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: The supply wire is shorted to another wire in the harness or the supply wire is shorted to engine ground. Repair the supply wire. Verify that the problem is resolved.
STOP
- Not OK - The voltage measurement is not 8.0 ± 0.4 VDC.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.
STOP