P04D3
- Powertrain
- Generic (SAE)
- Safety
Stop driving
Continuing to drive risks injury or major mechanical damage. Shut the engine off when it is safe to do so.
Exhaust Brake Input Circuit
This code is in our catalogue but has not yet been through editorial review, so the guidance below is limited to what our structured data supports. We publish deeper diagnostic content only after a code has been reviewed — here is why.
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.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Continuing to drive risks injury or major mechanical damage. Shut the engine off when it is safe to do so.
- Urgency
- Stop driving
- Will it pass emissions
- Not affected
- Check engine light
- Solid
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Open in switch circuit | Very common | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
- Exhaust Brake Request Switch
- Exhaust Brake Actuator
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Awaiting review
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