853789 Mercury STUD

Table 1
J1939 Code Code Description Comments
4374-5 Aftertreatment #1 DEF Pump #1 Motor Speed : Current Below Normal This code indicates there is problem with the DEF pump or the wiring harness.
4374-6 Aftertreatment #1 DEF Pump #1 Motor Speed : Current Above Normal This code indicates there is problem with the DEF pump or the wiring harness. Note: 372-5260 Test Kit is required for completing this procedure.
Illustration 1 g03185736
Table 2
Troubleshooting Test Steps Values Results
1. Check for Opens in the Pump Electronic Tank Unit (PETU) Wiring Harness for the DEF Pump Motor Circuit
A. Turn the keyswitch to the "OFF" position. The keyswitch must be OFF for 2 minutes to allow the DEF pump to purge, reset the code, and reset the DCU.
B. Disconnect the PETU wiring harness from the DEF pump and the Diesel Exhaust Fluid Controller (DCU).
C. Connect the 398-5063 Break-out Connector to the DCU connector.
Connect the 398-5056 Break-out Connector to the pump connector.
The connectors must be used to prevent damage to the DCU and pump connectors.
D. Measure the resistance between terminal 9 (PWM +) on the DEF pump connector and terminal 46 (PWM +) on the 86 pin DCU connector.
E. Measure the resistance between terminal 8 (PWM -) on the DEF pump connector and terminal 26 (PWM -) on the 86 pin DCU connector.
F. Measure the resistance between terminal 10 (PWM SIGNAL) on the DEF pump connector and terminal 24 (PWM SIGNAL) on the 86 pin DCU connector.
Open circuit
Result: There was less than 10 Ohms of resistance on all of the DEF pump motor circuit wires.
Proceed to Test Step 2.
Result: There was more than 10 Ohms of resistance on any one of the DEF pump motor circuit wires.
There is an open in the harness. Repair the wiring or replace the harness.
Verify that the problem is resolved.
Proceed to Test Step 4.
2. Check for Short Circuits in the PETU Wiring Harness for the DEF Pump Motor Circuit
A. Turn the keyswitch to the "OFF" position. The keyswitch must be OFF for 2 minutes to allow the DEF pump to purge, reset the code, and reset the DCU.
B. Disconnect the PETU wiring harness from the DEF pump and the DCU.
C. Connect the 398-5063 Break-out Connector to the DCU connector.
Connect the 398-5056 Break-out Connector to the pump connector.
The connectors must be used to prevent damage to the DCU and pump connectors.
D. Measure the resistance between terminal 9 (PWM +) on the DEF pump connector and a known good chassis ground.
E. Measure the resistance between terminal 8 (PWM -) on the DEF pump connector and a known good chassis ground.
F. Measure the resistance between terminal 10 (PWM SIGNAL) on the DEF pump connector and a known good chassis ground.
Short circuit
Result: There was more than 100 K Ohms of resistance between the connector terminal and ground on all of the DEF pump motor circuit wires.
Proceed to Test Step 3.
Result: There was less than 100 K Ohms of resistance between the connector terminal and ground on any one of the DEF pump motor circuit wires.
There is a short circuit in the harness. Repair the wiring or replace the harness.
Verify that the problem is resolved.
Proceed to Test Step 4.
3. Check for Short Circuits in the PETU Wiring Harness for the DEF Pump Motor Wiring
A. Turn the keyswitch to the "OFF" position. The keyswitch must be OFF for 2 minutes to allow the DEF pump to purge, reset the code, and reset the DCU.
B. Disconnect the PETU wiring harness from the DEF pump and the DCU.
C. Connect the 398-5063 Break-out Connector to the DCU connector.
The 398-5063 Break-out Connector must be used to prevent damage to the DCU connector.
D. Measure the resistance between terminal 46 (PWM +) and all other pins in the 86 pin DCU harness connector.
E. Measure the resistance between terminal 26 (PWM -) and all other pins in the 86 pin DCU harness connector.
F. Measure the resistance between terminal 24 (PWM SIGNAL) and all other pins in the 86 pin DCU harness connector.
Short circuit
Result: There was more than 100 K Ohms of resistance on all of the DEF pump motor circuit wires.
A failed DEF pump has been detected. Replace the DEF pump.
Proceed to Test Step 4.
Result: There was less than 100 K Ohms of resistance on any one of the DEF pump motor circuit wires.
There is a short circuit in the harness. Repair the wiring or replace the harness.
Verify that the problem is resolved.
Proceed to Test Step 4.
4. Perform a DEF Dosing System Verification Test
A. Turn the keyswitch to the "ON" position. Do not start the engine.
B. Connect to the "Diesel Exhaust Fluid Controller #1 ECM" using Cat ET.
C. Perform the "DEF Dosing System Verification Test" .
Diagnostic codes
Result: The code did not return.
Return the unit to service.
Complete the procedure in the order in which the steps are listed.