P2AA5: Exhaust Gas Recirculation Cooler Bypass Control Circuit Driver Current/Temperature Too High Bank 1
What to do
The car will drive normally; expect slower warm-up and possibly worse emissions. Ask for the bypass valve itself to be tested before the control module is replaced — a valve stiff with carbon produces this code, and a new module will report it again.
What this code means
The module's output driver for the EGR cooler bypass on bank 1 has exceeded its current or thermal limit.
An EGR cooler bypass exists because recirculated exhaust is wanted at two different temperatures. Cooled exhaust suppresses NOx best, so most of the time the gas goes through a heat exchanger. But during warm-up the engine wants that heat, both to reach operating temperature sooner and to light the catalyst faster — so a valve routes the exhaust around the cooler instead.
This code is about the driver rather than the valve, and the distinction decides who is at fault. The reasoning is the same as at P0E1E: a module switches the valve with a semiconductor driver that has its own limits, and the driver reporting an over-current usually means the load is excessive — a bypass valve stiff with carbon, drawing far more current than a free one.
So the module is protecting itself from the valve. Replacing the module with the stiff valve still attached reports the same code within days. Measure what the output drives before condemning what drives it.
Likely causes
Start here
- Restricted EGR passage · specialist
- Faulty EGR cooler bypass valve · specialist
- Damaged wiring harness · specialist
- Corroded or loose connector · specialist
Less common
- Control module driver failure · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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