U0120
Lost Communication with Starter/Generator Control Module
What it means
The Starter/Generator Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. Stop-start and mild-hybrid generator functions stop working. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
Is it safe to drive?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Starter/generator module unpowered
highOne of the most commonly reported causes for this code — check this first.
CAN wiring to starter/generator broken
mediumA plausible cause — test and verify before replacing parts.
Gateway module routing CAN messages incorrectly
lowLess common, but worth ruling out after the more likely causes.
Related help
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