FRAME AS-UPPER 3150905 - Caterpillar

Illustration 2 g01949487
Excitation Field Regulator (EFR) location under the forward end of the Generator (view: from right-hand side of the frame)
The following conditions could cause the Drivetrain ECM to activate this diagnostic code:
The EFR has an internal short circuit.
The power supply circuit is shorted to a ground source.
The ECM has failed. Test Step 1. CHECK THE SUPPLY VOLTAGE AT THE ECM
Turn the battery disconnect switch and the key start switch to the OFF position.
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ECM compartment in front of the cab
(1) Drivetrain ECM
(2) Chassis ECM
(3) Brake ECM
At the Drivetrain ECM, use a multimeter and the 7X-1710 "spoon" type multimeter probes to measure the voltage of the ECM 5 VDC supply. At the J1 harness connector, insert the positive multimeter probe along the supply positive contact J1-11 (wire E864). Insert the negative multimeter probe along the -battery contact J1-13 (wire A253-BK(Black)).
Turn the battery disconnect switch to the ON position. Turn the key start switch to the ON position. Do not start the engine.
Observe the voltage measurement. Expected Result:The voltage measurement is in the range of 5.0 0.3 VDC.Results:
OK - The voltage measurement is in the range of 5.0 0.3 VDC. The voltage of the power supply circuit is not below normal according to the voltage measurement. Proceed to Test Step 5.
NOT OK - The voltage measurement is less than 5.0 0.3 VDC. The power supply voltage is below normal. Proceed to Test Step 2.Test Step 2. CHECK THE ECM POWER SUPPLY AT THE ECM WITH THE CIRCUIT DISCONNECTED
Turn the battery disconnect switch and the key start switch to the OFF position.
At the Drivetrain ECM J1 harness connector, use a removal tool to remove the power supply positive circuit at contact J1-11 (wire E864) from the connector body.
Leave the negative multimeter probe inserted along the -battery contact J1-13 (wire A253-BK(Black)).
Turn the battery disconnect switch to the ON position. Turn the key start switch to the ON position. Do not start the engine.
At the J1 connector, measure the supply voltage with the circuit disconnected. Insert the positive multimeter probe through the vacant hole in the connector body in order to in contact with the ECM connector pin at the positive contact J1-11. Measure the voltage. Expected Result:The voltage measurement is in the range of 5.0 0.3 VDC.Results:
OK - The voltage measurement is in the range of 5.0 0.3 VDC. The voltage is correct. The ECM power supply is not causing the problem. Install the wires and socket that were removed from the J1 connector back into the original location. Ensure that the sockets are locked in place in the connector. There is a problem in the sensor circuit. Proceed to Test Step 3.
NOT OK - The voltage measurement is less than 4.7 VDC. The ECM power supply is not correct. Proceed to Test Step 5.Test Step 3. DISCONNECT THE EFRThe battery disconnect switch and the key start switch remain in the ON position.
Illustration 4 g01949610
EFR connectors
(4) Control Circuit connector
(5) Power connector
At the EFR, disconnect the control circuit harness