P2C51Fuel Level Sensor A/B Correlation
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Saddle tanks have two chambers and therefore two level senders, A and B; the engine module combines both resistances into one fuel level. GM's bulletin PI0926 for the 2011–2013 Equinox and Terrain shows this layout, with each sender reading about 40 Ω when full. P2C51 means the two senders disagree more than the tank design allows. A Hyundai patent describes such a check: it stores the voltage difference between both senders and starts its fault diagnosis when that difference stays the same although fuel has been used. No manufacturer publicly documents P2C51 itself; Ford and GM use P0461/P2066 and the stuck codes P25B0–P25B2 instead. CARB requires fuel level rationality because EVAP and misfire monitors rely on it.
- What you may notice
- Fuel gauge inaccurate or not reading full after filling
- Check engine lamp
- Range display jumps
- Likely causes
- LikelyWorn resistor track or sticking float on one sender
- PossibleJet pump not transferring fuel between the tank halves
- PossibleCorroded connector adding resistance on one sender
- RareWrong or misassembled sender after tank work
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.