CM850 Electronic Control System – FAULT CODE 434 Automotive Application

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Overview

ECM Power Supply Circuit SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned ON.

This fault code will be logged if a battery disconnect switch is used in the battery circuit to stop the engine. This fault code will also log if a battery disconnect switch is opened within 10 seconds of turning the keyswitch OFF.

Component Location

The ECM is connected to the battery by the OEM power harness through the ECM battery supply stub. This provides a constant power supply for the ECM. The location of the battery will vary with the OEM. Refer to the OEM troubleshooting and repair manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes

The ECM detects that primary ECM power supply dropped below 6.2 VDC while the keyswitch was in the ON position. The fault code will be active when the keyswitch is turned on following the incomplete power-down event.

Action Taken When the Fault Code is Active

• The ECM records the fault code immediately when the diagnostic runs and fails.
• Power-down data like trip information, maintenance monitor, and fault code information will not get saved to permanent memory when the keyswitch is turned off.

Conditions for Clearing the Fault Code

The ECM must see primary ECM battery voltage above 6.2 VDC when the keyswitch is turned off before the fault code will go inactive.

Shop Talk

This fault is set active if the ECM battery supply voltage drops below 6.2 VDC while the keyswitch is in the ON position.

Make sure the ECM unswitched battery supply is coming directly from the battery and not the starter. If unswitched power is coming from the starter, it is possible for the battery voltage to drop low enough during cranking to set this fault active.

This fault can also be caused by resistance in the ECM battery supply (+) or (-) circuits. Resistance in these circuits can cause the voltage level at the ECM input to drop low enough to set Fault Code 434 active.

This fault can also be caused by a short to ground in the injector wiring harness. Check the injector wires are oriented so that they will not interfere with a rocker lever or other component in the overhead system. Remove the valve cover and check for proper alignment of the injector wiring harness.

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 t05-434