G3516 TA Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with a sensor supply. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

Table 1

J1939 Code and Description	Comments
678-3 ECU 8 Volts DC Supply : Voltage Above Normal	The digital sensor supply voltage is above normal for 2 seconds. The code is logged.
678-4 ECU 8 Volts DC Supply : Voltage Below Normal	The digital sensor supply voltage is below normal for 2 seconds. The code is logged.
3509-3 Sensor Supply Voltage 1 : Voltage Above Normal	The analog sensor supply voltage is above normal for 2 seconds. The code is logged.
3509-4 Sensor Supply Voltage 1 : Voltage Below Normal	The analog sensor supply voltage is below normal for 2 seconds. The code is logged.
3510-3 Sensor Supply Voltage 2 : Voltage Above Normal	The analog sensor supply voltage is above normal for 2 seconds. The code is logged.
3510-4 Sensor Supply Voltage 2 : Voltage Below Normal	The analog sensor supply voltage is below normal for 2 seconds. The code is logged.
3511–6 Sensor Supply Voltage 3 : Current Above Normal	When the output driver for the oxygen sensors is on, the ECM detects a high current in the circuit for 2 seconds. The code is logged. The activation of this code is latched by the ECM. The power to the ECM must be powered to reset the power supply.

The ECM supplies 24 VDC to the voltage converter for the oxygen sensors through terminal location J1-10 at the ECM. The 3511-6 becomes activated if a short to ground is detected in the harness between the ECM and the voltage converter.

The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the digital sensors.

The ECM supplies a regulated voltage of 5.0 ± 0.2 VDC to the analog sensors.

The supply voltage for the sensors is routed from the ECM to terminal 1 of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal 2 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. Repair the sensor supply and check for any active sensor diagnostic codes to determine if a sensor has failed.

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat® Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged.	Codes	Result: A -3 or -4 code is active. Note which ECM is reporting the active code. Proceed to Test Step 2. Result: A -6 code is active. Proceed to Test Step 4.
2. Check for a Failed Sensor A. Connect Cat ET. B. Disconnect a sensor on the affected sensor supply circuit. C. Use Cat ET to monitor following: - Active code changes to logged D. Connect the affected sensor to the wiring harness. E. Repeat Step B through Step D for each sensor on the affected sensor supply.	Sensor	Result: The affected sensor supply active code changed to a logged code when a sensor is unplugged. Repair: Repair or replace the failed sensor. Verify that the repair eliminated the problem. Result: The affected sensor supply active code remains active after all the sensors on the sensor supply circuit have been checked. Repair: A failed wiring harness has been detected. Repair or replace the wiring harness. Verify that the repair eliminated the problem.
3. Check the Sensor Supply A. Turn the keyswitch to the OFF position. B. Unplug the sensor from the wiring harness. C. Install the jumper wire between the following terminals at the sensor connector: - Terminal 1 (sensor supply) and Terminal 2 (sensor return) D. Connect Cat ET. E. Use Cat ET to monitor the following: - Codes	Codes	Result: A -4 code is activated on the affected sensor supply. Repair: Remove the sensor. Check the sensor passage for a blockage or obstruction. Also, check for moisture frozen in the lines. If blockage is not found, replace the sensor. Verify that the repair eliminated the problem. Result: A -4 code is not activated on the affected sensor supply. Repair: The problem is in the wiring harness from the ECM to the sensor connector. Repair or replace the wiring harness. Verify that the repair eliminated the problem.
4. Disconnect the Voltage Converter While Monitoring the Active Diagnostic Codes A. Set the Engine control switch to the STOP position. B. Remove electrical power to the engine. C. Disconnect the connector for the voltage converter at the converter. D. Restore electrical power to the engine.	Codes	Result: The 3511-6 diagnostic code is no longer present when the voltage converter is disconnected. Repair: Replace the voltage converter. Result: The 3511-6 diagnostic code is still active with voltage converter disconnected. Repair: There is a short in the wiring harness between the voltage converter and the engine ECM. Repair or replace the harness.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).