Powertrain, generic (extended)

P2AA7 Engine Coolant Bypass Valve B Position Sensor Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Thermal management modules on modern engines use motor-driven rotary valves to split coolant between radiator, heater, oil or transmission cooler and engine block. A position sensor reports each valve's angle so the module can regulate it in closed loop. P2AA7 is the general circuit code for the sensor of valve B, used when the signal is unusable but cannot be classed as low (P2AA9) or high (P2AAA). No manufacturer documents P2AA7 publicly, and what valve B controls differs between makes. GM's 2025 diesel tables show how such a sensor is read on valve C: digitally over SENT, with readings outside a fixed count window filed as low or high faults after 4 seconds in 5, Type B. CARB counts these cooling actuators among the monitored components. Expect slow warm-up or temperature swings.

Likely causes

Loose, corroded or coolant-wetted connector, or damaged sensor wiring
Lost 5 V supply or ground to the position sensor
Failed position sensor inside the valve module
Faulty sensor input in the engine control module

Symptoms

  • Malfunction indicator lamp on
  • Slow warm-up or reduced cabin heating
  • Fluctuating or elevated coolant temperature reading

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
Time0.5–3 h

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

Parts involved

engine coolant bypass valve b position sensorwiring harnessecm

Related codes

P2AA8P2AA9P2AAAP2AABP26A4P23C3

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