Powertrain
generic / SAE
P2256
O2 Sensor Heater Control Circuit Low Bank 1 Sensor 2
The ECU detects a low-side voltage below threshold on the heater control of the rear oxygen sensor on bank 1. The heater driver may be stuck on or shorted to ground.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number2 / 56
Possible causes
- Heater wire shorted to ground high
- Internal heater short medium
- Connector pins corroded - high contact resistance low
Symptoms
- Check engine light on after several drive cycles
- Slightly increased fuel consumption during cold start
- Delayed entry into closed-loop fuel control
- Failed emissions inspection (lambda readiness)
Inspection / repair
- Difficulty: medium
- DIY: possible
- Estimated cost: 100–400 €
- Estimated time: 0.5–1.5 h
- Component: oxygen sensor
- Component: oxygen sensor heater circuit
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012