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.
Medium severity. Can I keep driving?You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.
Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.
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
Most 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
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P2AA5 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- A: Hybrid or air and fuel
- A5: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2AA5?
You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.
What causes code P2AA5?
The most common causes are: bypass flap binding on soot or corrosion, motor working against resistance; internal fault in the bypass actuator motor; partial short between the motor wires.
Related codes
- P2AA6EGR Cooler Bypass Control Circuit Driver Current/Temperature Too High Bank 2
- P245AEGR Cooler Bypass Control Circuit/Open (Bank 1)
- P245CEGR Cooler Bypass Control Circuit Low (Bank 1)
- P245DEGR Cooler Bypass Control Circuit High (Bank 1)
- P24A5EGR Cooler Bypass Control Stuck/Open (Bank 1)
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.