ELECTRICAL AR 4540242 - Caterpillar

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 0.2 VDC to the 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. If any of the diagnostic codes are active, a sensor may have been damaged. Repair the sensor supply and check for any active sensor diagnostic codes to determine if a sensor has been damaged.
Illustration 1 g06104265
Engine ECM
Illustration 2 g06104962
Selective Catalyst Reduction (SCR) Controller
Illustration 3 g06104945
Engine ECM with PWM sensors
Illustration 4 g03740995
Sensor connector
(1) Sensor supply
(2) Sensor return
(3) Signal
Table 2
Sensor Supply Sensor Supply ECM Location
Sensor Supply #1 Sensors on A5:E4 engine ECM J2 connector or A5:E2 aftertreatment controller J2 connector
Sensor Supply #2 Sensors on A5:E4 engine ECM J1 connector Probable Causes
Codes
SensorRecommended Actions
Table 3
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 or logged. Note which ECM is reporting the active code.
Proceed to Test Step 2.
Result: A -21 code is active or logged.
Proceed to Test Step 3.
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:
- Codes
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. Create a Short at the Sensor Connector
A. Turn the keyswitch to OFF.
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 became active.
Repair: Perform the following:
1. Remove the sensor.
2. Check the sensor passage for a blockage or obstruction.
3. 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 did not become active.
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.
If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer