What it means
The EGR cooler bypass valve on bank 1 is mechanically stuck in the open (bypassing) position - EGR always bypasses the cooler, gas reaches the intake hotter than designed.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 1 EGR cooler bypass directs exhaust gas either through the cooler or around it before it returns to the intake. P24A5 means the bypass remains open, so bank 1 EGR gas can reach the intake hotter than intended and increase NOx emissions or cause poor running.
Common causes
Most likely first.
- Valve stuck open
- Carbon or debris buildup preventing free movement
- Component wear with age - mechanical play
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
How to diagnose it
- Check freeze-frame data and related EGR faults to see under what engine conditions the bank 1 bypass position was detected.
- Inspect the bank 1 bypass valve, linkage, and nearby passages for carbon buildup, debris, or mechanical damage.
- Check the bypass actuator connector and wiring for loose pins, corrosion, or heat damage.
- Use the scan tool's available actuator test to compare commanded and observed bank 1 bypass position.
- Check the position feedback circuit, if fitted, against the manufacturer's diagnostic procedure to distinguish a stuck valve from a faulty signal.
Common fixes
- Clean carbon or debris from the bank 1 bypass mechanism if permitted by the service procedure.
- Repair damaged wiring or a loose bank 1 actuator connector.
- Replace the bank 1 bypass valve or actuator if it remains mechanically stuck or fails its test.
Can I keep driving?
Avoid heavy acceleration and high engine loads if the engine pings, knocks, or loses power; hotter EGR gas can worsen these symptoms and increase NOx emissions. Arrange repair soon, especially if knocking is pronounced.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.