P20EBReductant Control Module Power Relay De-Energized Performance - Too Late
- 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
- Here the opposite of P20EA happens: after the reductant control module has finished its after-run and released the power relay, voltage is still present on the switched side, so the relay opens late or not at all. Typical reasons are welded contacts, a control line shorted to ground that keeps the coil energised, or a module that never ends its shut-down. The DEF module, pump and heaters may then stay powered with the engine off, which drains the battery and keeps the system awake. No maker documents P20EB publicly. The check mirrors P068B on the engine module, which Saab's 2011 9-5 diesel derives from the relay control circuit, and Ford's 2023 diesel summary flags a reductant relay voltage above 0 V while the output stage is off (P21C7). CARB requires such SCR components to be monitored.
- What you may notice
- Check engine light
- Battery drained after the vehicle has been parked
- DEF pump or relay audible long after switching off
- Likely causes
- LikelyWelded or sticking relay contacts
- PossibleRelay control line shorted to ground, keeping the coil energised
- RareReductant control module or network activity preventing shut-down
- 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: €20 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.