SHAFT 9K8856 - Caterpillar

Table 1 lists the diagnostic codes for the Diesel Exhaust Fluid (DEF) pump circuit.
Table 1
J1939 Code and Description CDL Code and Description Comments
4334–3
Aftertreatment #1 DEF #1 Pressure (absolute) : Voltage Above Normal 3090–3
Aftertreatment #1 DEF Pressure #1 Sensor : Voltage Above Normal There is excessive voltage on the signal wire between the Diesel Exhaust Fluid Controller (DCU) and the DEF pump or there is an open circuit on the supply, signal, or return wire.
The code is logged.
4334–4
Aftertreatment #1 DEF #1 Pressure (absolute) : Voltage Below Normal 3090–4
Aftertreatment #1 DEF Pressure #1 Sensor : Voltage Below Normal There is low voltage on the signal wire between the DCU and the DEF pump pressure sensor.
The code is logged. Note: 372-5260 Test Kit is required for completing this procedure.
Illustration 1 g06229120Complete the procedure in the order in which the steps are listed.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Opens in the Pump Electronic Tank Unit (PETU) Wiring Harness for the DEF Pump Pressure Sensor Circuit
A. Turn the keyswitch to the OFF position for 2 minutes. The keyswitch must be OFF for 2 minutes to allow the DEF pump to purge, reset the code, and reset the Diesel Exhaust Fluid Controller (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 DEF pump connector.
The connectors must be used to prevent damage to the DCU and DEF pump connector.
D. Measure the resistance between terminal 2 (SUPPLY) on the DEF pump connector and terminal 19 (SUPPLY) on the 86-pin DCU connector.
E. Measure the resistance between terminal 3 (SIGNAL) on the DEF pump connector and terminal 17 (SIGNAL) on the 86-pin DCU connector.
F. Measure the resistance between terminal 4 (GROUND) on the DEF pump connector and terminal 18 (GROUND) on the 86-pin DCU connector.
Open Circuit
Result: There was less than 10 Ohms of resistance on all of the DEF pump pressure circuit wires.
Proceed to Test Step 2.
Result: There was more than 10 Ohms of resistance on any one of the DEF pump pressure circuit wires.
Repair: 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 Pressure Sensor Circuit
A. Turn the keyswitch to the "OFF" position.
B. Disconnect the PETU wiring harness from the DEF pump and the DCU.
C. Connect the 398-5056 Break-out Connector to the DEF pump connector.
The connector must be used to prevent damage to the DEF pump connector.
D. Measure the resistance between terminal 2 (SUPPLY) on the DEF pump connector and a known good chassis ground.
E. Measure the resistance between terminal 3 (SIGNAL) on the DEF pump connector and a known good chassis ground.
F. Measure the resistance between terminal 4 (GROUND) 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