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 | ||
|---|---|---|
| Description | Conditions which Generate this Code | System Response |
| 262-3 5 Volt Sensor DC Power Supply voltage above normal | The analog sensor supply voltage is above normal for two seconds. | 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 two seconds. | |
| 263-3 Digital Sensor Power Supply (8V Or 12V) voltage above normal | The digital sensor supply voltage is above normal for two seconds. | |
| 263-4 Digital Sensor Power Supply (8V Or 12V) voltage below normal | The digital sensor supply voltage is below normal for two seconds. | |
System Operation
The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:
- Atmospheric pressure sensor
- Coolant temperature sensor
- Crankcase pressure sensor
- Filtered engine oil pressure sensor
- Filtered fuel pressure sensor
- Turbocharger outlet pressure sensor
- Left turbocharger inlet pressure sensor
- Right turbocharger inlet pressure sensor
- Unfiltered engine oil pressure sensor
- Unfiltered fuel pressure sensor
The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the following sensors:
- Left exhaust temperature sensor
- Right exhaust 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 the diagnostic code 262-3 or the diagnostic code 263-3 is logged, it is possible that all of the sensors have 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 | g01212476 |
Typical schematic | |
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| Illustration 2 | g01212477 |
Typical 8 V supply | |
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| Illustration 3 | g01212479 |
P1 ECM connector (P1-2) 5 V sensor supply (P1-3) Sensor return (P1-4) 8 V supply (P1-5) Digital return (P1-7) Coolant temperature sensor (P1-11) Left exhaust temperature (P1-12) Right exhaust temperature (P1-16) Filtered engine oil pressure sensor (P1-17) Unfiltered engine oil pressure sensor (P1-24) Filtered fuel pressure (P1-25) Unfiltered fuel pressure | |
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| Illustration 4 | g01288476 |
P2 ECM connector (P2-36) Turbocharger outlet pressure sensor (P2-37) Atmospheric sensor (P2-38) Left turbocharger inlet pressure sensor (P2-39) Right turbocharger inlet pressure sensor (P2-46) Crankcase pressure sensor | |
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| Illustration 5 | g01094844 |
Sensor connector (Pin A) Sensor supply (Pin B) Sensor return (Pin C) Signal | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the "main disconnect switch (MDS)" to the OFF position.
- Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.
Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
- Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" 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.
- Turn the "MDS" to the ON position.
- Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Look for the following diagnostic codes:
- 262-3
- 262-4
- 263-3
- 263-4
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- 262-3
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, "Inspecting Electrical Connectors".
STOP
- Not OK - Either the 262-3 or 262-4 diagnostic code is active at this time. Proceed to Test Step 3.
- Not OK - Either the 263-3 or 263-4 diagnostic code is active at this time. Proceed to Test Step 5.
Test Step 3. Disconnect the 5 Volt Sensors while you Monitor the Active Diagnostic Codes
- Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 Volt 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
- Coolant temperature sensor
- Crankcase pressure sensor
- Filtered engine oil pressure sensor
- Filtered fuel pressure sensor
- Turbocharger outlet pressure sensor
- Left turbocharger inlet pressure sensor
- Right turbocharger inlet pressure sensor
- Unfiltered engine oil pressure sensor
- Unfiltered fuel pressure sensor
- Atmospheric pressure sensor
- Disconnect the following sensors one at a time:
- Turn the "MDS" to the OFF position.
Expected Result:
The diagnostic code deactivates when a particular sensor is disconnected.
Results:
- OK - The 262-3 or 262-4 diagnostic code deactivates when a particular 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 262-3 or 262-4 diagnostic code remains active after all of the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Proceed to Test Step 4.
Test Step 4. Check the 5 Volt Supply Voltages at the ECM
- Disconnect the J1/P1 ECM connector.
- 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.
- Remove the wires from terminal locations P1-2 (5 V sensor supply) and P1-3 (sensor return). Install a jumper wire into each of these terminal locations.
- Connect the J1/P1 ECM connector.
- Turn the "MDS" to the ON position.
- Measure the voltage between the jumper wire in P1-2 (5 V sensor supply) and the jumper wire in P1-3 (sensor return).
- Turn the "MDS" to the OFF position.
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.
STOP
- Not OK - The voltage measurement is not 5.0 ± 0.2 VDC.
Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".
STOP
Test Step 5. Disconnect the 8 Volt Sensors while you Monitor the Active Diagnostic Codes
- Monitor the active diagnostic code screen on Cat ET while you disconnect each 8 Volt sensor at the sensor connector. Check for an active 263-3 code or an active 263-4 code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Disconnect the following sensors one at a time:
- Exhaust temperature sensor (LH)
- Exhaust temperature sensor (RH)
- Exhaust temperature sensor (LH)
- Disconnect the following sensors one at a time:
- Turn the "MDS" to the OFF position.
Expected Result:
The diagnostic code deactivates when a particular sensor is disconnected.
Results:
- OK - The 263-3 or 263-4 diagnostic code deactivates when a particular 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 263-3 or 263-4 diagnostic code remains active after the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Proceed to Test Step 6.
Test Step 6. Check the 8 Volt Supply Voltage at the ECM
- Disconnect the J1/P1 ECM connector.
- 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.
- Remove the wires from terminal locations P1-4 (8 V sensor supply) and P1-5 (sensor return). Install a jumper wire into each of these terminal locations.
- Connect the J1/P1 ECM connector.
- Turn the "MDS" to the ON position.
- Measure the voltage between the jumper wire in P1-4 (8 V sensor supply) and P1-5 (sensor return).
- Turn the "MDS" to the OFF position.
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.
STOP
- Not OK - The voltage measurement is not 8.0 ± 0.4 VDC.
Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".
STOP