P21ABReductant Level Sensor B Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P21AB is the high-side counterpart: GM sets it when level sensor 2 shows an open load (between 3.56 and 4.74 V, read 1.5 ms after the test pulse) or a short to battery voltage (above 4.74 V), each for more than 3 s, as Type A on the 6.6L LML and the 2014 Cruze diesel. GM's preliminary bulletin PIP4887B for 2010–2011 Silverado, Sierra, Express and Savana with the LML or LGH engine names P21AB together with P203D and P21B0 and the message Service Exhaust Fluid System: inspect wiring, connectors and terminal tension also when the faults are merely stored, and replace the DEF tank only when the wiring is sound. For the 2011 model year GM sorted P21AB into its tamper-related group.
- What you may notice
- Check engine light on at once
- Service Exhaust Fluid System message
- Several level sensor codes stored together
- Likely causes
- LikelyOpen signal wire or spread terminal at the tank connector
- PossibleSignal wire shorted to a voltage source
- PossibleLevel sensor B open inside the tank assembly
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.