P2478Exhaust Gas Temperature Out of Range (Bank 1 Sensor 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Unlike the circuit codes, P2478 judges the temperature itself at the first exhaust probe of bank 1, usually ahead of the oxidation catalyst. Ford's 2015 diesel summary for the 6.7L and 3.2L engines groups it with the EGT circuit check: the test is high-side only and trips at roughly 1150 °C, because the PTC probe curve leaves no separate low threshold. Volkswagen's 2014 Golf data for the 2.0L TDI CJAA sets it when the gap between target and measured temperature exceeds 40 K, and bulletin 01 12 28 updated the 2012 Passat TDI (CKRA) software because the check was too sensitive. Overheating from overfuelling or a failing turbo is the real-world trigger, so the cause deserves attention before the probe.
- What you may notice
- MIL on
- Power reduced to protect the exhaust parts
- Smoke or a hot smell from the exhaust in real overheating
- Likely causes
- LikelyReal overheating from excess fuel or a leaking injector
- PossibleOverly sensitive diagnosis needing a software update (VW Passat 2012)
- PossibleProbe reading too high due to ageing
- RareLack of air from a boost leak or turbocharger fault
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.