Powertrain, generic (extended)

P2BA2 Engine Coolant Pump Stuck/Stalled

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

P2BA2 belongs to the electric main water pump. GM uses it in a way the title does not suggest: on the 2.7-litre L3B (table 19OBDG03D) and in the 2025 table 25OBDG03B the test runs while the pump should be switched off – pump disabled or a request of 0–4 rpm for at least 3 s – and fails if the pump still reports 10 rpm or more for 8 of 10 seconds with over 11 V on board. So GM looks for a pump that keeps turning, Type B with MIL after two trips. A real blocked rotor shows up in GM's scheme as underspeed P2B85. Possible causes are faulty pump electronics, a speed signal that is not plausible, or coolant flow driving the impeller. When the pump will not stop, the engine warms up more slowly. Overspeed with air is P26CE, the command circuit P26CA.

Likely causes

Pump electronics ignoring the off command

Implausible speed feedback from the pump

Impeller turned by coolant flow from another pump

Command or enable line fault keeping the pump on

Symptoms

Check engine light after two trips
Engine takes longer to reach operating temperature
Pump audible after the engine is switched off

Repair estimate

DifficultyHardWorkshop job

Parts and labour€100–1,200

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine coolant pumpengine coolant loop

Related codes

P2B85 P26CE P26CB P26CA P26D2

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.