P2B87Coolant Pump A Underspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- With P2B87 the reported speed of coolant pump A stays below the commanded one. GM's 2025 tables (25OBDG03A, 25OBDG04B) compare filtered command and feedback against a calibrated limit while 300–3,480 rpm is requested and more than 11 V is present; 8 s in a 10 s window, Type B. Ford's 2024 gasoline summary lists it as the underspeed type of the cabin-heating auxiliary pump, checked continuously from 11 V. On GM vehicles the code often had no hardware cause: PIT5789 (2021 Tahoe, Suburban, Yukon, Escalade) cured it with new BCM software, bulletin 21-NA-024 (2021–2022 Acadia, Blazer, Enclave, Traverse, XT5, XT6) with an HVAC module update – the G17 pump was not to be replaced. PIT6505 later found a stray O-ring in it. Overspeed is P2B86, stall P2B9C.
- What you may notice
- Check engine light, often without any other complaint
- Reduced cabin heat at idle or with the engine stopped
- Likely causes
- LikelyOutdated software in the module that commands the pump
- PossibleImpeller slowed by debris or a foreign O-ring
- PossibleWorn bearing or motor in the auxiliary pump
- RareLow voltage or poor contact at the pump connector
- 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: €50 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.