W166 No‑Start – TCM/ISM Missing, Low Voltage at Fuses
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ML350
W166 No‑Start – TCM/ISM Missing, Low Voltage at Fuses
I’m working on a Mercedes W166 (2015 ML350) with a persistent no‑start condition. Removed the ECM to replace #4 coil and reinstalled. Now I'm facing a no start condition where the ISM is not letting the car start a it thinks its not in park.
Here’s what I’ve observed so far:
- Fault codes: U002886 (CAN drivetrain fault) and U012087 (lost communication with TCM).
- Symptoms: ISM and TCM are missing from the scan tool, vehicle won’t crank/start.
- Voltage checks: Only ~1 volt present at fuse 215, 216, 217 in the Front SAM (F58) with the car powered on. I did replace the aux battery just to verify.
- Modules online: ECM is alive and reporting communication faults, but drivetrain modules are offline.
I know that a mismatch VIN could cause issues, but it seems that the TCM is not even getting correct power. Could the upstream SAM fuse be the issue? Or is this totally a mismatched VIN, ECM short or an upstream fuse issue. Spent a good 7 hours on this.
Here’s what I’ve observed so far:
- Fault codes: U002886 (CAN drivetrain fault) and U012087 (lost communication with TCM).
- Symptoms: ISM and TCM are missing from the scan tool, vehicle won’t crank/start.
- Voltage checks: Only ~1 volt present at fuse 215, 216, 217 in the Front SAM (F58) with the car powered on. I did replace the aux battery just to verify.
- Modules online: ECM is alive and reporting communication faults, but drivetrain modules are offline.
I know that a mismatch VIN could cause issues, but it seems that the TCM is not even getting correct power. Could the upstream SAM fuse be the issue? Or is this totally a mismatched VIN, ECM short or an upstream fuse issue. Spent a good 7 hours on this.
Last edited by RileyRRC; Dec 7, 2025 at 06:55 PM.
