OBD-II code · Powertrain (generic)
P04D3 Exhaust Brake Input Circuit
The exhaust brake activation input - typically from a stalk lever, brake pedal switch, or vehicle bus message - shows a circuit fault. The ECU cannot accept a request to engage the exhaust brake, which limits engine braking on heavy vehicles.
Is it safe to drive with P04D3?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen in switch circuit
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.6–1.8 h
- Emissions test
- Usually unaffected
- Parts involved
- Exhaust Brake Request Switch, Exhaust Brake Actuator
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.