BODY AS-PUMP 2928769 - Caterpillar

Note: Refer to Troubleshooting, "Component Location" for the locations of the components listed in this procedure.
Illustration 1 g06150953
(1) Terminal Tube Heater
(2) Terminal Power (12V)
(a) Terminals
(b) Return Tube Heater
(c) DCU Connector
(A) To Heater Relay (12V)
Illustration 2 g03892866The ground for the DEF Tube Heaters come from the Ground Heater Relay. Refer to the machine electrical schematic. The Ground Heater Relay for the DEF Tubes should be an open circuit unless the heaters are activated by the DCU.Refer to Systems Operation, "DEF Dosing Control System", and Systems Operation, "Cold-Weather Operation" for when the heaters are activated:
Terminal 1 (3): Always grounded by harness to machine frame
Terminal 5 (86):Always have 12 V that is received from 30A Fuse Assembly (13-RP-16)
Terminal 2 (85): When DCU activates the DEF Tube Heaters, this will be grounded by the DCU Terminal 5.
Terminal 4 (87): When DCU activates the DEF Tube Heaters, this will be grounded by the DCU Terminal A.
Illustration 3 g03892884
Table 2
Troubleshooting Test Steps Values Results
1. Checking Resistance for Tube Heater
A. Unplug the tube heater line for corresponding code and check resistance across the two pins (1) and (2).
Approximately 8.6 ohms/m (Suction Tube)
Approximately 3.2 ohms/m (Delivery Tube)
Approximately 2.5 ohms/m (Return Tube)
Result: Resistance is not correct.
Repair: Replace the corresponding tube heater.
Result: Resistance is correct.
Proceed to Test Step 2
2. Check for Proper Grounding
A. Does the Ground Heater Relay have proper ground and power going to it.
Yes or No
Result: No.
Repair: Then troubleshoot the harnesses to determine root cause.
Result: Yes.
Proceed to Test Step 3.
3. Check the Ground Heater Relay
A. Disconnect the battery and then swap the Ground Heater Relay with the adjacent relay which is power for the DCU.
Did problem stay with the relay
Result: Yes.
Repair: Replace the relay.
Result: No.
Proceed to Test Step 4.
4. Check the Resistance Battery and DCU
A. Measure the resistance between the DCU and the battery positive.
Approximately 1,000 ohms or higher
Result: No.
Repair: Replace the DCU.
Result: Yes.
Repair: This is a harness issue.
Go back to step 1.