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2017 AMG C 43 (W205); 2019 E 300 (W213); 2008 ML 320 CDI (W164)
I was 5 hours into a long trip when the glow plug light came on for a minute and then went off again. Three minutes later, same thing. Eventually, still on the same trip, the glow plug light came on and stayed on. The next day the vehicle started as normal, but now both the glow plug light and the CEL were on. Three days later the vehicle started to have difficulty to start when cold. The OBD II scanner gave an error "Communication to Glow Plug Control Module lost".
I replaced all 6 glow plugs and the glow plug control unit with new parts from the Mercedes dealership. I took care that the part numbers and the glow plug Voltage of the new parts were correct for the VIN of the vehicle and also that the new part numbers correctly cross referenced to the old part numbers. The glow plug light and CEL still remain on, or come back on even when the error code is deleted on the OBD II scanner. I checked all the fuses in the fuse box in the engine bay. No sign of damaged or loose wires or broken connectors. Everything in the engine bay is clean and in good order. I don't know what else could be wrong. Some help would be appreciated. Thank you.
https://www.obd-codes.com/u0106
Out of 5 possibilities this site list, 4 are bad wiring.
Get a can of MAF or other cleaner, wash all the plugs on the line to module and get good light to observe the harness for cuts.
2017 AMG C 43 (W205); 2019 E 300 (W213); 2008 ML 320 CDI (W164)
Thank you very much kajtek1. The problem was indeed a poor earth wire connection to the cylinder head. After cleaning the wire lug and connecting surface on the cylinder head with some sandpaper, the error code, CEL and Glow Plug Light error are gone. The engine again starts first time like it always used to.
This earth wire connection was very slightly loose and just a little corroded. Cleaning and tightening the connection resolved the error code, CEL and Glow Plug Light error.
Glad you found it. I think I'll run thru my engine compartment this weekend and check for chafing and loose/corroded connections. This is a great thread.
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