MBE 900 DDEC VI Troubleshooting – Section 4.5 Faulty MCM

Section 4.5
Faulty MCM

To determine if a faulty MCM control unit is causing the cylinder to misfire, install a test MCM.‪

Note: Carefully disengage the lock tab on the vehicle wiring harness and engine wiring harness connectors when removing. Follow instructions in the “MCM” section of the MBE 900 service manual, fuel system chapter.

Section 4.5.1
Faulty MCM Repair

There is no authorized repair for the MCM.‪

Section 4.5.1.1
Verification of Replacement for Faulty MCM

Perform the following steps to determine if the test MCM has resolved the misfiring cylinder condition:‪

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.‪

1. Start the engine.
2. Increase the engine speed up to the occurrence of the misfiring.
3. Listen for misfiring cylinder.
   1. If the engine is not misfiring, shut down the engine. No further troubleshooting is required. Replace the MCM with a new unit.
   2. If the engine is misfiring, shut down the engine, install original MCM, and check for worn or damaged valves and cylinder kits; refer to "4.6 Worn or Damaged Valve or Cylinder Kit" .