What it means
Reductant Injection Valve Circuit Low (Bank 1 Unit 1): the signal voltage is below the expected range. This valve doses reductant (DEF/AdBlue) into the exhaust for SCR NOx reduction.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The reductant injection valve for Bank 1 Unit 1 meters DEF into the exhaust for SCR NOx reduction. P2048 sets when the control module detects voltage below the expected range in that valve circuit, which can indicate a short to ground or another circuit fault.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Review freeze-frame data and related reductant dosing or NOx codes to identify the conditions when the Bank 1 Unit 1 circuit voltage went low.
- Inspect the Bank 1 Unit 1 valve connector and harness for chafing, damaged insulation, moisture, corrosion, or a wire contacting ground.
- Check terminal fit and inspect the valve circuit for a short to ground using the manufacturer's wiring information.
- Test circuit voltage and continuity, then check the valve solenoid winding against the manufacturer's specification.
- Clear the code after repair and confirm that Bank 1 Unit 1 valve operation and circuit readings are normal.
Common fixes
- Repair wiring chafed through to ground near the Bank 1 Unit 1 valve.
- Clean or replace corroded valve connector terminals and correct poor terminal contact.
- Replace the Bank 1 Unit 1 injection valve if it causes the low circuit reading and the wiring is sound.
Can I keep driving?
Limit driving while the DEF or NOx warning is active, particularly if a no-start countdown has begun. A low circuit fault can prevent Bank 1 Unit 1 from dosing, increasing NOx emissions and risking an emissions test failure or eventual no-start.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.