C121C — manufacturer-specific chassis code

C121C is a manufacturer-specific chassis code: it is defined by the carmaker, not by the OBD-II standard, so the same code can mean different things on different brands. Below are the vehicles and failure patterns where owners report it, drawn from NHTSA complaints — the most reliable guide to what it means in practice.

In our record, C121C is reported most often on Jeep, Volkswagen and Chrysler vehicles , against powertrain and engine failure patterns , across 2007–2016 model years. Jeep alone accounts for 67% of them.

In ProblemsByVin's analysis of the NHTSA owner-complaint record, owners cite C121C across 6 vehicle failure patterns. Diagnostic codes in complaints are reported by owners and are unverified — they point to where this code shows up, not a confirmed diagnosis. Open a page below for the full pattern (symptoms, mileage, repair costs owners cite).

Vehicles where owners report C121C 6 patterns

Codes are pulled from what owners wrote in their NHTSA filings — they're allegations, not a shop diagnosis. Always confirm with a live scan. Browse all diagnostic codes →