CM850 Electronic Control System – FAULT CODE 1684

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Overview

Circuit: Catalyst Tank Heater Relay SMALL | MEDIUM | LARGE

Circuit Description

The catalyst tank heater keeps the catalyst solution from freezing in the catalyst tank. The catalyst tank heater is also used to thaw a frozen catalyst solution tank. The catalyst heater element is powered by the catalyst tank heater relay.

Component Location

The catalyst tank heater is located in the catalyst tank. The location of the catalyst tank heater relays will vary by OEM.

Shop Talk

This fault code cannot detect any circuit failures on the heater side of the relay. Only circuit errors between the ECM and the relay can be detected by this fault code.

Possible causes of this fault code include:

• A shorted catalyst tank heater relay
• Catalyst tank heater signal wire shorted to ground.

On-Board Diagnostics (OBD) Information (Euro 4 Certified Engines):

• The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
• The ECM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. The MIL lamp and fault code can also be cleared using the INSITE™ service tool.
• The fault code will be cleared from memory after 40 consecutive drive cycles where the diagnostic runs and passes.

On-Board Diagnostics (OBD) Information (Euro 4 Stage 1+ Certified Engines):

• The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
• An engine torque derate will be activated after 50 hours of engine operation with the fault code active.
• The ECM turns OFF the malfunction indicator lamp (MIL) after 1 ignition cycle that the diagnostic runs and does not fail. The MIL lamp cannot be cleared using the INSITE™ service tool.
• The fault code will be cleared from memory after 400 days or 9600 hours of engine operation.

Refer to Troubleshooting Fault Code t05-1684