P2051
Reductant Injection Valve Circuit Low Bank 2 Unit 1
Auxiliary emissions (SCR/reductant)
Generic OBD-II
Medium
What it means
P2051 means the engine/SCR control module has detected low voltage (a likely short-to-ground) in the circuit for the reductant injection valve on bank 2, unit 1. This valve meters DEF (reductant) into the exhaust to cut NOx, so the fault is an emissions-system issue rather than something you'll feel in how the engine drives. Left unrepaired, diesels may eventually derate.
Medium
Can I keep driving? Drivable short-term, but diesel SCR faults can trigger a speed/power derate if ignored; repair soon to stay legal and avoid limp mode.
Common symptoms
What you'll notice
- Check-engine light on (often with an emissions/DEF warning)
- SCR or exhaust-treatment warning messages
- Possible reduced-power/derate warning if the fault persists (diesel)
- Usually little change in how the engine feels
Common causes
Most likely first
- Short-to-ground or low voltage in the reductant injection valve wiring (bank 2, unit 1)Likely
- Failed reductant (DEF) injection valveCommon
- Corroded or loose connector at the injection valveCommon
- Damaged or chafed harness in the circuitLess often
- Faulty ECM/PCM or SCR control moduleLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for companion reductant/SCR codes.
- Inspect the injection valve connector and wiring for a short-to-ground, corrosion, or damage; repair as needed.
- Measure the valve's resistance against spec and replace it if out of range.
- Confirm the valve's supply and control feed are correct with the circuit powered.
- If wiring and valve test good, have the SCR/ECM module evaluated. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2051?+
Short-term driving is usually fine, but the SCR system won't dose reductant correctly and diesels may derate. Fix it promptly.
Can I just clear P2051?+
It returns once the ECM re-tests the injection valve circuit, so the low-voltage fault or valve needs repair.
Related codes
Often seen with P2051
Read & clear P2051 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX