TUBE AS 7C8258 - Caterpillar

Table 3
Troubleshooting Procedure for the Engine ECM Power Supply
Troubleshooting Test Steps Value Results
1. Check the Voltage at the Ignition Keyswitch Input
A. Turn the keyswitch to the OFF position.
B. Disconnect the connector for the ignition keyswitch.
C. Measure the voltage at the battery supply input to the ignition keyswitch.
Battery voltage
Result: The measured voltage is equal to battery voltage.
Reconnect the connector for the ignition keyswitch. Proceed to Test Step 2.
Result: The measured voltage is not equal to battery voltage.
Repair: Replace the wiring between the battery and the input to the ignition keyswitch.
Use the electronic service tool to clear all logged diagnostic codes. Verify that the repair eliminates the fault.
2. Check the Keyswitch Signal Voltage
A. Turn the keyswitch to the OFF position.
B. Disconnect the P1 connector from the ECM.
C. Turn the keyswitch to the ON position. Do not attempt to start the engine.
D. Measure the voltage between P1:69 and a suitable ground.
Battery voltage
Result: The measured voltage is equal to battery voltage.
Proceed to Test Step 4.
Result: The measured voltage is not equal to battery voltage.
Proceed to Test Step 3.
3. Check the Wiring Between the Keyswitch and the ECM
A. Turn the keyswitch to the OFF position.
B. Disconnect the connector for the ignition keyswitch.
C. Measure the resistance between the keyswitch "ON" terminal on the harness and P1:69.
Less than 2.0 Ohms
Result: The resistance is less than 2.0 Ohms.
Repair: Replace the ignition keyswitch.
Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
Result: The resistance is greater than 2.0 Ohms.
Repair: Replace the wiring between the ignition keyswitch and the ECM.
Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
4. Check for Battery Voltage at the ECM Connector
A. Turn the keyswitch to the ON position.
B. Measure the resistance between the following points:
P1:81 and P1:84
P1:82 and P1:85
P1:83 and P1:86
Battery voltage
Result: The measured voltage is equal to battery voltage.
Contact the Dealer Solutions Network (DSN).
Result: The measured voltage is not equal to battery voltage.
Repair: Replace the wiring between the battery and the ECM.
If the procedure did not correct the issue, contact the Dealer Solutions Network (DSN).
Table 4
Troubleshooting Procedure for the NOx Sensor Power Supplies
Troubleshooting Test Steps Value Results
1. Check the Voltage at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Disconnect the connector for the suspect NOx sensor.
C. Turn the keyswitch to the ON position.
D. Measure the voltage between terminal 1 and terminal