Powertrain, generic (extended)

P2AA5 EGR Cooler Bypass Control Circuit Driver Current/Temperature Too High Bank 1

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

P2AA5 comes from the H-bridge that drives the DC motor of the bank 1 EGR cooler bypass flap: the driver chip itself reports that it is getting too hot. GM's diesel summary tables carry this monitor from 2017 (17OBDG04) to 2025 (25OBDG04A) as a motor overtemperature check. The fault flag comes from the hardware layer when the bridge exceeds 170 °C; the test runs outside cranking with powertrain relay voltage above 11 V, needs 160 failures in 200 samples at a 12.5 ms task and is Type B. GM bundles it with the open and shorted circuit codes P245A, P245C and P245D as an actuator fault. A flap that binds on soot, a motor with internal damage or a partial short make the bridge work too hard. A flap stuck in one position is P24A5; bank 2 is P2AA6.

Likely causes

Bypass flap binding on soot or corrosion, motor working against resistance

Internal fault in the bypass actuator motor

Partial short between the motor wires

Overheating or faulty H-bridge in the engine control module

Symptoms

Malfunction indicator lamp on after two trips
Bypass flap no longer driven, so warm-up EGR cooling stays at its last state
Possible further EGR or cooler efficiency codes

Repair estimate

DifficultyHardWorkshop job

Parts and labour€150–1,200

Time1–4 h

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

Parts involved

egr cooler bypass valve b1ecm

Related codes

P2AA6 P245A P245C P245D P24A5

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