P2BA0Coolant Pump C Underspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2BA0 reports that coolant pump C does not reach its speed. GM names the code Low Temperature Coolant Loop Pump Underspeed in its diesel ECM tables and treats it as a low out-of-range speed reading: in 2020 (20OBDG04) the printed limit is below -100 rpm in 5 of 8 one-second samples, in 2025 (25OBDG04A) below -50 rpm in 4 of 5; enable conditions are an active pump, 11 V or more at the relay and no cranking. Type B, so the lamp waits for a second faulty trip. Bulletin 21-NA-149 lists P2BA0 among the many codes caused by a chafed engine harness on the 3.0-litre LM2 Duramax in 2021 trucks and SUVs, next to P2C48 for the same pump. Besides wiring, a stuck or worn pump and air in the loop are suspects. Pump B is P2B9F, pump D P2BA1.
- What you may notice
- Check engine light after the second faulty trip
- Parts on the low-temperature loop cooled less, reduced power possible
- Further electrical codes when the harness is damaged
- Likely causes
- LikelyEngine harness chafed against brackets, shorting pump circuits
- PossibleWorn or partly seized low-temperature loop pump
- RareAir or low coolant in the low-temperature loop
- RareLow supply voltage at the pump relay
- 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: €100 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.