C175-20 Locomotive Engine Caterpillar

Manifold DEF Temperature Is Low

Usage:

Use this procedure to troubleshoot a low DEF temperature. Also, use this procedure if the following event code is active or logged.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
4337-17 Aftertreatment #1 DEF Doser #1 Temperature : Low - least severe (1)	E936(1) Low Aftertreatment #1 DEF Temperature #1	The DEF manifold temperature is low.
4337-18 Aftertreatment #1 DEF Doser #1 Temperature : Low - moderate severity (2)	E936(2) Low Aftertreatment #1 DEF Temperature #1	The DEF manifold temperature is low.

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Table 2
Associated Codes
J1939 Code	CDL Code	Troubleshooting Procedure
4357-5	3604-5	Troubleshooting, "Solenoid Valve - Test"
4357-6	3605-6	Troubleshooting, "Solenoid Valve - Test"

Probable Causes

Codes
DEF manifold heater
Relay

Recommended Actions

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Table 3
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Apply electrical power to the engine. B. Connect Cat^® Electronic Technician (ET) to the service tool connector. C. Look for active codes that are associated with the system for the event code.	Codes	Result: An associated code is present. Repair: Troubleshoot any associated codes before continuing with this test. Result: A 4337 code is present. Proceed to Test Step 2.
2. Check the DEF Manifold Heater A. Remove electrical power from the engine. B. Disconnect the DEF manifold heater from the wiring harness connector. C. Apply electrical power to the engine. D. Connect Cat ET. E. Use Cat ET to activate the following overrides: - "Aftertreatment #1 DEF Manifold Heater Relay Override" F. Measure the voltage on the DEF manifold heater wiring harness connector.	24 VDC	Result: There was NOT 24 VDC at the DEF tank manifold connector. Proceed to Test Step 3. Verify that the repair eliminated the problem. Return to service. Result: There was 24 VDC at the DEF manifold connector. A failed manifold heater has been detected. Repair: Replace the DEF manifold heater. Verify that the repair eliminated the problem.
3. Check the DEF Tank Heater Relay Load Circuit A. Apply electrical power to the engine. B. Connect Cat ET. C. Use Cat ET to activate the following overrides: - "Aftertreatment #1 DEF Manifold Heater Relay Override" D. Measure the voltage between terminal 4 at the DEF manifold heater relay wiring harness connector and a known good ground.	24 VDC	Result: There was 24 VDC at the DEF manifold heater relay connector. There is a problem with the wiring between the DEF manifold heater and the DEF manifold heater relay. Repair: Repair or replace the wiring harness. Verify that the repair eliminated the problem. Result: There was NOT 24 VDC at the DEF manifold heater relay connector. Proceed to Test Step 4.
4. Check the Power Supply to the DEF Manifold Heater Relay A. Apply electrical power to the engine. B. Measure the voltage between the DEF manifold heater relay power supply terminal 1 and a known good ground.	24 VDC	Result: There was 24 VDC between the DEF manifold heater relay power supply terminal 1 and a known good ground. Repair: Replace the DEF manifold heater relay. Verify that the repair eliminated the problem. Result: There was NOT 24 VDC between the DEF manifold heater relay power supply terminal 1 and a known good ground. There is a problem with the wiring between the 24 VDC power supply on the engine interconnect harness and the DEF manifold heater relay. Repair: Repair or replace the wiring harness. Verify that the repair eliminated the problem.

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).