CONE 4B7941 - Caterpillar

Table 1 lists the diagnostic codes for the Diesel Exhaust Fluid (DEF) pump circuit.
Table 1
Diagnostic Trouble Codes    
J1939 Code    CDL Code    Code Description    Comments    
4334-3     3090-3     Aftertreatment 1 Diesel Exhaust Fluid Doser Absolute Pressure : 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     3090-4     Aftertreatment 1 Diesel Exhaust Fluid Doser Absolute Pressure : Voltage Below Normal     There is low voltage on the signal wire between the DCU and the DEF pump pressure sensor.
The code is logged.    
Follow the troubleshooting procedure in order to identify the root cause of the problem.    Note: 372-5260 Test Kit is required for completing this procedure.
Illustration 1 g03184659
Complete 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