C175 Tier 4 Final Engines for Off-Highway Trucks Caterpillar

Use this procedure to troubleshoot a problem with the Diesel Exhaust Fluid (DEF) pump motor. Also, use this procedure if one of the following event codes is active or easily repeated.

Table 1

J1939 Code and Description	CDL Code and Description	Comments
3361-5 Aftertreatment #1 DEF Dosing Unit : Current Below Normal	3102-5 Aftertreatment #1 DEF Dosing Pump : Current Below Normal	This code indicates that there is problem with the Diesel Exhaust Fluid (DEF) pump or the wiring harness.
3361-6 Aftertreatment #1 DEF Dosing Unit : Current Above Normal	3102-6 Aftertreatment #1 DEF Dosing Pump : Current Above Normal	This code indicates that there is problem with the DEF pump or the wiring harness.
4451–5 Aftertreatment #2 DEF Dosing Unit : Current Below Normal	3109–5 Aftertreatment #2 DEF Dosing Unit : Current Below Normal	This code indicates that there is problem with the DEF pump or the wiring harness.
4451–6 Aftertreatment #2 DEF Dosing Unit : Current Above Normal	3109–6 Aftertreatment #2 DEF Dosing Unit : Current Above Normal	This code indicates that there is problem with the DEF pump or the wiring harness.
7457-5 Aftertreatment #1 DEF Dosing Unit #2 : Current Below Normal	5032–5 Aftertreatment #1 Diesel Exhaust Fluid Pump #2 : Current Below Normal	This code indicates that there is problem with the DEF pump or the wiring harness.
7457-6 Aftertreatment #1 DEF Dosing Unit #2 : Current Above Normal	5032–6 Aftertreatment #1 Diesel Exhaust Fluid Pump #2 : Current Above Normal	This code indicates that there is problem with the DEF pump or the wiring harness.
7462–5 Aftertreatment #2 Diesel Exhaust Fluid Dosing Unit #2 : Current Below Normal	5033–5 Aftertreatment #2 Diesel Exhaust Fluid Dosing Unit #2 : Current Below Normal	This code indicates that there is problem with the DEF pump or the wiring harness.
7462–6 Aftertreatment #2 Diesel Exhaust Fluid Dosing Unit #2 : Current Above Normal	5033–6 Aftertreatment #2 Diesel Exhaust Fluid Dosing Unit #2 : Current Above Normal	This code indicates that there is problem with the DEF pump or the wiring harness.

Table 2

Required Tools		Qty
372-5260	Test Kit	1

Illustration 1	g06201026

Illustration 2	g06100059
(1) Aftertreatment #1 Diesel Exhaust Fluid (DEF) Pump #1 (2) Aftertreatment #1 DEF Pump #2 (3) Aftertreatment #2 DEF Pump #1 (4) Aftertreatment #2 DEF Pump #2 (5) Aftertreatment #1 Dosing Control Unit (DCU) #1 (6) Aftertreatment #1 DCU #2 (7) Aftertreatment #2 DCU #1 (8) Aftertreatment #2 DCU #2

Table 3

Troubleshooting Test Steps	Values	Results
1. Check the Pump Electronic Tank Unit (PETU) Wiring Harness for the DEF Pump Motor for an Open Circuit A. Turn the keyswitch to "OFF". The keyswitch must be OFF for 2 minutes to allow the DEF pumps to purge, reset the code, and reset the DCU. B. Disconnect the PETU wiring harness from the affected DEF pump and the affected Diesel Exhaust Fluid Control Unit (DCU). C. Connect the 398-5063 Probe to the DCU wiring harness connector. D. Connect the 398-5056 Probe to the pump wiring harness connector. The probe must be used to prevent damage to the DCU and pump wiring harness connectors. E. Measure the resistance between the following terminals affected DEF pump wiring harness connector and the affected 86-pin DCU wiring harness connector: - Terminal 9 (PWM +) on the DEF pump wiring harness connector and Terminal 46 (PWM +) on the 86-pin DCU wiring harness connector. - Terminal 8 (PWM -) on the DEF pump wiring harness connector and Terminal 26 (PWM -) on the 86-pin DCU wiring harness connector. - Terminal 10 (PWM SIGNAL) on the DEF pump wiring harness connector and Terminal 24 (PWM SIGNAL) on the 86-pin DCU wiring harness connector.	Open Circuit	Result: There were less than 10 Ohms of resistance on all the DEF pump motor circuit wires. Proceed to Test Step 2. Result: There were more than 10 Ohms of resistance on any one of the DEF pump motor circuit wires. Repair: There is an open in the wiring harness. Repair or replace the wiring harness. If the problem is not resolved, proceed to Test Step 4.
2. Check the PETU Wiring Harness for the DEF Pump Motor for a Short Circuit A. Turn the keyswitch to "OFF". 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 affected DEF pump and the affected DCU. C. Connect the 398-5063 Probe to the DCU wiring harness connector. D. Connect the 398-5056 Probe to the pump wiring harness connector. The probe must be used to prevent damage to the DCU and pump wiring harness connectors. E. Measure the resistance between the following terminals on the affected DEF pump wiring harness connector and a known good chassis ground: - Terminal 9 (PWM +) on the DEF pump wiring harness connector and a known good chassis ground. - Terminal 8 (PWM -) on the DEF pump wiring harness connector and a known good chassis ground. - Terminal 10 (PWM SIGNAL) on the DEF pump wiring harness connector and a known good chassis ground.	Short Circuit	Result: There were more than 100 K Ohms of resistance between the connector terminal and ground on all the DEF pump motor circuit wires. Proceed to Test Step 3. Result: There were less than 100 K Ohms of resistance between the connector terminal and ground on any one of the DEF pump motor circuit wires. Repair: There is a short circuit in the wiring harness. Repair or replace the wiring harness. If the problem is not resolved, proceed to Test Step 4.
3. Check the PETU Wiring Harness for the DEF Pump Motor Wiring for a Pin to Pin Short Circuit A. Turn the keyswitch to "OFF". 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 affected DEF pump and the affected DCU. C. Connect the 398-5063 Probe to the affected DCU wiring harness connector. The probe must be used to prevent damage to the DCU wiring harness connector. D. Measure the resistance between the following terminals in the affected 86-pin DCU wiring harness connector: - Terminal 46 (PWM +) and all other pins in the 86-pin DCU wiring harness connector. - Terminal 26 (PWM -) and all other pins in the 86-pin DCU wiring harness connector. - Terminal 24 (PWM SIGNAL) and all other pins in the 86-pin DCU wiring harness connector.	Short Circuit	Result: There were more than 100 K Ohms of resistance on all the DEF pump motor circuit wires. Repair: A failed DEF pump has been detected. Replace the DEF pump. Proceed to Test Step 4. Result: There were less than 100 K Ohms of resistance on any one of the DEF pump motor circuit wires. Repair: There is a short circuit in the wiring harness. Repair or replace the wiring harness. If the problem is not resolved, proceed to Test Step 4.
4. Perform an "Aftertreatment Dosing System Functional Test" A. Turn the keyswitch to "ON". Do not start the engine. B. Connect to Cat® Electronic Technician (ET). C. Select the "Selective Catalyst Reduction System". D. Use Cat ET to perform the following diagnostic test: - "Aftertreatment Dosing System Functional Test" Refer to Troubleshooting, Cat ET Service Features for additional information. Note: When the test prompts to proceed to clear active diagnostic codes, select "ACCEPT".	Test	Result: The test was successful. Return to service.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).