12320 Mercury BRACKET

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 two seconds.
The code is logged.
678-4
ECU 8 Volts DC Supply : Voltage Below Normal The digital sensor supply voltage is below normal for two seconds.
The code is logged.
3509-3
Sensor Supply Voltage 1 : Voltage Above Normal The analog sensor supply voltage is above normal for two seconds.
The code is logged.
3509-4
Sensor Supply Voltage 1 : Voltage Below Normal The analog sensor supply voltage is below normal for two seconds.
The code is logged.
3510-3
Sensor Supply Voltage 2 : Voltage Above Normal The analog sensor supply voltage is above normal for two seconds.
The code is logged.
3510-4
Sensor Supply Voltage 2 : Voltage Below Normal The analog sensor supply voltage is below normal for two seconds.
The code is logged.
Illustration 1 g06156557
For the complete circuit details, refer to the full schematic.
Illustration 2 g06135678
For the complete circuit details, refer to the full schematic.
System OperationThe 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 Active Diagnostic Codes and Check for Logged Diagnostic Codes
A. Connect Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Download the "Product Status Report" from the engine ECM before performing any troubleshooting or clearing diagnostic trouble codes.
C. Monitor the active diagnostic code screen on Cat ET. Record any active diagnostic codes.
Note. Wait at least 30 seconds in order for diagnostic codes to become active.
Logged Diagnostic Codes
Or
Active Diagnostic Codes
Results: A diagnostic code is logged but is not active.
Repair: Do not troubleshoot a logged code unless the code relates to an operator complaint. If the code is logged and the code does not relate to an operator complaint, clear the code.
If the logged code relates to this procedure, inspect the electrical connectors and the wiring for the circuit.
Refer to Troubleshooting, "Electrical Connectors - Inspect"
Results: A -3 code or -4 code is active for the 8 V digital supply.
Proceed to Test Step 2.
Results: A -3 code or -4 code is active for one of the 5 V analog supplies.
Proceed to Test Step 5.
2. Inspect the Electrical Connectors and the Wiring
A. Check the harness and the wiring for abrasion and for pinch points.
B. Thoroughly inspect all connectors that are in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
-3 code
or
-4 code
for
8 V digital supply
Results: The connectors and wiring are OK.
Proceed to Test Step 3.
Results: The connectors and/or wiring are NOT OK.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
3. 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.
C. One at a time, disconnect each 8 V sensor from the circuit for the code and recheck the active diagnostic code screen.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
-3 code
or
-4 code
for
8 V digital supply
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 the connectors. Verify that the problem is resolved.
Results: The 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 4.
4. Check the Digital Supply Voltage at the ECM
A. At the ECM harness connector, remove the supply wire and remove the return wire, for the circuit for the code.
B. Using appropriate terminals, fabricate two jumper wires.
C. At the ECM harness connector, install one jumper wire into the supply terminal location and install one jumper wire into the return terminal location.
D.Measure the voltage between the jumper wires.
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.
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. Before you consider replacing the ECM, consult with your Cat dealer Technical Communicator (TC) for assistance.
5. Inspect the Electrical Connectors and the Wiring
A. Check the harness and the wiring for abrasion and for pinch points.
B. Thoroughly inspect all connectors that are in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
-3 code
or
-4 code
for
5 V analog supply
Results: The connectors and wiring are OK.
Proceed to Test Step 6.
Results: The connectors and/or wiring are NOT OK.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
6. 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.
C. One at a time, disconnect each 5 V sensor from the circuit for the code and recheck the active diagnostic code screen.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
-3 code
or
-4 code
for
5 V analog supply
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 the connectors. Verify that the problem is resolved.
Results: The diagnostic code remains active after all the sensors are disconnected. The sensors are not the cause of the diagnostic