Posted on by

Electronic Control System Gas Plus Engines – FAULT CODE 346

ECM Software Error

Overview

CODE REASON EFFECT
Fault Code: 346
PID: 253
SPN: 630
FMI: 12
LAMP: Yellow
SRT: 

ECM software error.

None.

ECM Power-down Error
SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) is a computer that is responsible for engine control, diagnostics, and user features.

Component Location

The ECM is located on the side of the engine, next to the ignition control module (ICM).

Shop Talk

This fault code can be caused by an internal ECM problem. This can also be caused if battery power is disconnected before power-down sequence is completed. Repairs to the ECM are not possible.

Cautions and Warnings

 CAUTION 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Read the fault codes. Fault Code 346 active?
  STEP 1B. Check the power supply. Constant +12-VDC power supply to the ECM?
  STEP 1C. Check the ECM ground. More than 100k ohms?
  STEP 1D. Recalibrate the ECM. Fault Code 346 active after recalibration?
STEP 2. Clear the fault codes.  
  STEP 2A. Disable the fault code. Fault Code 346 inactive?
  STEP 2B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Read the fault codes.

Conditions

  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

Read the fault codes.

Fault Code 346 active?
YES NO
No Repair No Repair

Guided Step 1B – Check the power supply.

Conditions

  • Turn keyswitch ON.

Action

  • Inspect the power supply to the ECM
  • Check the OEM connector as a possible source of an intermittent power supply
  • Make certain the power supply to the ECM is constant and not intermittent.

Constant +12-VDC power supply to the ECM?
YES NO
No Repair

Intermittent power supply to the 31-pin OEM connector. Refer to the OEM service manual.

Guided Step 1C – Check the ECM ground.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness connector 1 and connector 2 from the ECM.

Action

  • Measure the resistance from engine block ground to all pins in the ECM connector ports.
  • Measure the resistance from battery (-) post to all pins in the ECM connector ports.

More than 100k ohms?
YES NO
No Repair
  • Replace the ECM.
  • Call for pre-authorization.
  • Refer to Procedure 019-031.

Guided Step 1D – Recalibrate the ECM.

Conditions

  • Turn keyswitch OFF
  • Connect all components.

Action

Fault Code 346 active after recalibration?
YES NO
  • Replace the ECM.
  • Call for pre-authorization.
  • Refer to Procedure 019-031.
 No Repair

Guided Step 2 – Clear the fault codes.

Guided Step 2A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

  • Start the engine and let it idle for one minute.
  • Verify that Fault Code 346 is inactive.

Fault Code 346 inactive?
YES NO
No Repair

Troubleshooting procedures need to be repeated from the beginning.

Guided Step 2B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

  • Use INSITE™ electronic service tool to erase the inactive fault codes.

All fault codes cleared?
YES NO
No Repair

Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting charts
Last Modified:  03-Aug-2004
Avatar photo

Published by Jack

Hello, I'm Jack, a diesel engine fan and a blogger. I write about how to fix and improve diesel engines, from cars to trucks to generators. I also review the newest models and innovations in the diesel market. If you are interested in learning more about diesel engines, check out my blog and leave your feedback.