3516C Locomotive Engines Selective Catalytic Reduction Caterpillar

Use this procedure in order to troubleshoot a problem with a low DEF level of the DEF main tank or use this procedure if the following event code is active. Refer to Troubleshooting, "Event Codes" for information about event codes.

Note: The term Diesel Exhaust Fluid (DEF) and the word reagent are used interchangeably in some code descriptions and labels.

Table 1

Event Code
Code and Description	Conditions which Generate this Code	System Response
E954 (1) Low Aftertreatment #1 SCR Catalyst Reagent Tank #1 Level	The DEF level of the DEF main tank is below the trip point for the programmed delay time.	The code is logged. Dosing is disabled until the pressure is correct.
E954 (2) Low Aftertreatment #1 SCR Catalyst Reagent Tank #1 Level

Note: Use Cat ET to verify any suspected code. Determine what codes are present. Evaluate all codes for possible interaction. Refer toTroubleshooting, "Diagnostic Trouble Codes" and Troubleshooting, "Event Codes" for direction.

Probable Causes

• DEF main tank is empty

• DEF leak

• DEF filter screen is plugged

• DEF level sensor failed

• DEF manifold air leak

• DEF fill valve (pneumatic) not actuating

• DEF fill valve (solenoid) not actuating

Recommended Actions

DEF Main Tank is Empty

Check the DEF main tank level and ensure that all supply valves are open.

DEF Leak

Check all DEF tanks and supply lines for leaks.

Repair any leaks immediately.

DEF Filter Screen is Plugged

Determine if the DEF filter screen is plugged and replace if necessary. The screen is located at the dosing control cabinet.

DEF Level Sensor Failed

Determine if the DEF main tank is low.

If the tank is not low, troubleshoot the DEF main tank level sensor.

DEF Manifold Air Leak

Check the DEF manifold for an air leak

An air leak will not allow the DEF fill valve (pneumatic) to actuate.

Note: Pay close attention to o-ring seals and air purge valves.

DEF Fill Valve (Pneumatic) not Actuating

Determine if the DEF fill valve (pneumatic) is actuating.

Shut off the DEF supply to the dosing cabinet.

While leaving the air control line to the valve attached, remove the DEF fill valve (pneumatic).

Activate the "Aftertreatment #1 SCR Catalyst Reagent Refill Valve Override" to ON in order to open the solenoid valve.

This action should cause the DEF fill valve (pneumatic) to be open.

Ensure the air control line for the DEF fill valve (pneumatic) is not leaking.

Ensure the DEF fill valve (pneumatic) is moving with the valve command.

The plunger on the DEF fill valve (pneumatic) should be seen moving up and down.

DEF Fill Valve (Solenoid) not Actuating

Determine if the DEF fill valve (solenoid) is actuating.

Shut off the DEF supply to the dosing cabinet.

Remove the air control line from the DEF fill valve (pneumatic).

Activate the "Aftertreatment #1 SCR Catalyst Reagent Refill Valve Override" to ON in order to open the DEF fill valve (solenoid).

This action should cause a steady stream of air from the line.