Electronic Control System ISM and QSM11 Engines – FAULT CODE 343

Electronic Control Module (ECM)


Overview

CODE REASON EFFECT
Fault Code: 343
PID: S254
SPN: 629
FMI: 12/12
LAMP: Yellow
SRT: 

Internal ECM error.

Possibly none on performance, or severe derate.

Electronic Control Module
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Circuit Description

The ECM monitors both signal voltage output to the injectors and ECM input from the engine position sensor.

Component Location

The ECM is located on the fuel pump side of the engine.

Shop Talk

  • Loose engine or chassis ground connections can cause Fault Code 343 to be logged. Pay special attention to the negative starter post connection.
  • Moisture in the ECM connectors can also cause the ECM to log Fault Code 343.
  • Symptoms can include intermittent stumble or rough running.

Note: It is always a good idea to check the resistance of the meter leads by reading the resistance displayed by the tool when touching the positive and negative leads together. Subtract this reading from any readings taken for resistance. This will provide a more accurate resistance measurement. Note: Always reapply dielectric grease when reconnecting an electrical connection.

Refer to Troubleshooting Fault Code t05-343

Last Modified:  02-Sep-2010