P04D6Exhaust Brake Input Circuit High
- 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
- The exhaust brake input is the driver's request for the exhaust or engine brake – a button or stalk on diesel pick-ups and trucks. On GM's 6.6-litre L5P, for example, the button must be pressed again after every start. GM uses the exhaust brake status as an enable condition for other emission monitors, which is why CARB requires the input to be checked. No manufacturer table available to us lists P04D3–P04D7; Hino's J08E truck engine checks P04D5 before its exhaust brake function test. P04D6 means the input voltage stays above its upper threshold – the signal line is shorted to the supply, or with a pull-up input the button ground or signal line is open.
- What you may notice
- Exhaust brake cannot be switched on, button lamp off or wrong
- Possibly check engine light
- More load on the service brakes downhill
- Likely causes
- LikelySignal line shorted to supply voltage
- PossibleButton ground or signal line open (pull-up logic)
- PossibleButton faulty internally
- RareCorroded or wet connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.