Transmission Control System MIL Request Circuit/Open
The dedicated MIL request line from the TCM to the ECM (used in older systems where modules used a hard wire to ask for the MIL instead of CAN messaging) is open. The ECM cannot honour TCM-side MIL requests.
Affected components
- Mil request wire
- Tcm
- Ecm
Common causes
- High likelihood: Open MIL request wire
- Low likelihood: Pin pushed back out of connector body
- Low likelihood: Cracked solder joint inside the module or sensor
Possible symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.