3512B and 3512C Petroleum Generator Set Engines Caterpillar

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.

Table 1

Diagnostic Codes Table
Description	Conditions which Generate this Code	System Response
262-3 5 Volt Sensor DC Power Supply short to +batt	The analog sensor supply voltage is above normal for 2 seconds.	The code is logged. All sensors are set to default values.
262-4 5 Volt Sensor DC Power Supply short to ground	The analog sensor supply voltage is below normal for 2 seconds.
263-3 Digital Sensor Supply short to +batt	The digital sensor supply voltage is above normal for 2 seconds.
263-4 Digital Sensor Supply short to ground	The digital sensor supply voltage is below normal for 2 seconds.

System Operation

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

• Aftercooler temperature sensor

• 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 turbocharger turbine inlet temperature sensor

• Right turbocharger turbine inlet 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, all of the sensors could have been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has failed.

Illustration 1	g03317117
Typical schematic for the +5V supply sensors

Illustration 2	g03318025
Typical schematic for the +8V supply sensors

Illustration 3	g03323203
Terminal locations at the P1 ECM connector (P1-2) Analog supply (P1-3) Analog return (P1-4) Digital Supply (P1-5) Digital Return (P1-11) Left-hand turbo inlet exhaust temperature (P1-12) Right-hand turbo inlet exhaust temperature (P1-16) Filtered oil pressure (P1-17) Unfiltered oil pressure (P1-24) Filtered fuel pressure (P1-25) Unfiltered fuel pressure (P1-35) Analog return (P1-39) Analog supply

Illustration 4	g03323204
Terminal locations at the P2 ECM connector. (P2-36) Turbo outlet pressure (P2-37) Atmospheric pressure (P2-38) Left turbo inlet pressure (P2-39) Right turbo inlet pressure (P2-46) Crankcase pressure (P2-54) Digital return (P2-56) Digital supply

Illustration 5	g01240891
Sensor connector (Terminal 1) Sensor supply (Terminal 2) Sensor return (Terminal 3) Signal

Table 2

Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect connectors (1) through (7). Inspect all of the connectors that are associated with the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit. D. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. E. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.	Connectors	Results: The harness and connectors appear to be OK. Proceed to Test Step 2 Results: 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 coupled. Verify that the repair eliminates the problem.
2. Check for Diagnostic Codes that are Active or Logged A. Connect Caterpillar Electronic Technician (ET) to the service tool connector. B. Restore the electrical power to the ECM. C. Monitor the active diagnostic code screen on Cat ET. Check and record any diagnostic codes that are active or logged. Look for the following diagnostic codes: - 678-3 - 678-4 - 3509-3 - 3509-4 - 3510-3 - 3510-4 Note: Wait at least 30 seconds in order for the diagnostic codes to become active. D. Turn the main disconnect switch to the OFF position.	Codes	Results: No diagnostic codes are active or logged. Repair: There does not appear to be an electrical problem with the sensor supply at this time. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Results: Either the 678-3 or 678-4 diagnostic code is active or logged at this time. There is an electrical problem with the digital sensor supply. Proceed to Test Step 6 Results: Either the 3509-3, 3509-4, 3510-3, or 3510-4 diagnostic code is active or logged at this time. There is an electrical problem with the analog sensor supply. Proceed to Test Step 3
3. Check the Supply Voltage at the Sensor Connector A. Disconnect the harness connectors for the following sensors: - Crankcase pressure sensor - Jacket water pressure sensor - Filtered oil pressure sensor - Unfiltered oil pressure sensor - Filtered fuel pressure sensor - Unfiltered fuel pressure sensor - RH turbo inlet pressure sensor - LH turbo inlet pressure sensor - Atmospheric pressure sensor - Intake manifold pressure sensor B. Restore the electrical power to the appropriate ECM. Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition. C. Measure the voltage between terminals 1 and 2 at the appropriate sensor connector. D. Turn the main disconnect switch to the OFF position. E. Connect all of the sensors.	5.0 ± 0.2 VDC	Results: Each voltage measurement is 5.0 ± 0.2 VDC. Repair: The analog supply is reaching the sensor connector. There may be a problem with the sensor. Perform the following procedure: 1. Clear all diagnostic codes. 2. Run the engine. Allow the engine to warm up. Check if the code has been logged again. If the code becomes active or logged, the sensor is faulty. Replace the sensor. Verify that the repair eliminated the problem. If the code does not become active or logged, there may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct troubleshooting procedure. Results: At least one voltage measurement is not 5.0 ± 0.2 VDC. There is a problem with the harness wiring or with the ECM. Proceed to Test Step 4
4. Disconnect the Analog Sensors While You Check for Active Diagnostic Codes A. Restore the electrical power to the ECM. B. Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 V sensor at the sensor connector. Check for an active 3509-3, 3509-4, 3510-3, or (3510-4) code. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. C. For a problem with the supply at the primary ECM, disconnect the following sensors one at a time: - Atmospheric pressure sensor - Crankcase pressure sensor - Intake manifold pressure sensor - Filtered oil pressure sensor - Unfiltered oil pressure sensor - Filtered fuel pressure sensor - Unfiltered fuel pressure sensor - Jacket water coolant pressure sensor - Left turbocharger inlet pressure sensor - Right turbocharger inlet pressure sensor D. For a problem with the supply at the secondary ECM, disconnect the following sensors one at a time: - Filtered oil pressure sensor - Filtered fuel pressure sensor - Turbocharger outlet pressure sensor - Unfiltered engine oil pressure sensor - Jacket water coolant pressure sensor E. Turn the main disconnect switch to the OFF position.	Analog sensors	Results: The 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 repair eliminated the problem. Results: The diagnostic code remains active after all of the sensors are disconnected. The sensors are not the cause of the diagnostic code. Leave the sensors disconnected. Proceed to Test Step 5
5. Check the Analog Supply Voltages at the ECM A. Disconnect the J1/P1 and J2/P2 connectors from the appropriate ECM. B. Fabricate five jumper wires that are long enough to be used to measure the supply voltage at the ECM connector. Crimp connector sockets to one end of each jumper wire. C. Remove the wires from the sensor supplies at the following terminal locations: - P2-82 - P2-72 - P2-80 - P2-81 Also remove the wire from P2-54 (analog return). Install a jumper wire into each of these terminal locations. D. Connect the ECM connectors. E. Restore electrical power to the engine ECM. F. One at a time, measure the voltage between the jumpers in each of the sensor supplies listed above and the jumper for the analog return. G. Turn the main disconnect switch to the OFF position.	5.0 ± 0.2 VDC	Results: The voltage measurement is 5.0 ± 0.2 VDC. Repair: The ECM is operating correctly. The supply wire that is in the harness is shorted to another wire in the harness or the supply wire is shorted to engine ground. Repair the harness wiring that is between the sensor and the ECM connector. Verify that the repair eliminated the problem. Results: The voltage measurement is not 5.0 ± 0.2 VDC. Repair: The ECM is not producing the correct supply voltage. There appears to be a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance.
6. Disconnect the Digital Sensors while you Check for Active Diagnostic Codes A. Restore the electrical power to the ECM. B. Monitor the active diagnostic code screen on Cat ET while you disconnect each of the digital sensors at the sensor connector. Check for an active 678-3 code or an active 678-4 code. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. C. Disconnect the following sensors one at a time: - Sensor for the left turbocharger turbine inlet temperature - Sensor for the right turbocharger turbine inlet temperature D. Turn the main disconnect switch to the OFF position.	Codes	Results: The 678-3 or 678-4 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 repair eliminated the problem. Results: The 678-3 or 4678-4 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 7
7. Check the Digital Supply Voltage at the ECM A. Disconnect the J2/P2 and J1/P1 ECM connector. B. Fabricate three 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. C. Remove the wires from terminal locations P2-29 (digital sensor supply) P1-18 (digital return) and P1-5 (digital return). Install a jumper wire into each of these terminal locations. D. Connect the J2/P2 ECM connector. E. Restore electrical power to the engine ECM. F. Measure the voltage between the jumper wire in P2-29 (digital sensor supply) and P1-18 (sensor return). Measure the voltage between the jumper wire in P2-29 (digital sensor supply) and P1-5 (sensor return). G. Turn the main disconnect switch to the OFF position.	8.0 ± 0.4 VDC	Results: 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 repair eliminated the problem. Results: The voltage measurement is not 8.0 ± 0.4 VDC. Repair: The ECM is not producing the correct supply voltage. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance.