What it means
The EGR cooler does not lower exhaust gas temperature as expected — typically internal coolant fouling, a partial blockage, or a cracked cooler that mixes coolant with exhaust gas.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The EGR cooler transfers heat from recirculated exhaust gas to the engine coolant before the gas returns to the intake. The control module assesses cooler effectiveness from temperature information, and sets P2457 when the exhaust gas is not being cooled as expected, such as when soot restricts the cooler or a crack lets coolant leak into the exhaust.
Common causes
Most likely first.
- Cooler internally clogged with soot
- Cooler cracked, coolant entering exhaust
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
- Use a scan tool to record freeze-frame data and compare EGR-related exhaust temperatures under the conditions that set the code.
- With the engine cool, inspect the EGR cooler and nearby exhaust and coolant connections for soot deposits, coolant residue, leaks, or signs of a crack.
- Check coolant level and look for unexplained coolant loss or white exhaust smoke, which can point to coolant entering the exhaust through the cooler.
- Inspect the cooler passages and temperature-sensor wiring and connectors for soot blockage, damage, or poor contact.
- If external checks do not explain the temperature readings, test cooler flow and temperature response using the manufacturer's procedure.
Common fixes
- Repair a leaking or damaged coolant connection at the cooler.
- Clean a soot-restricted EGR cooler if the manufacturer permits cleaning.
- Replace a cracked or internally blocked EGR cooler.
- Repair damaged temperature-sensor wiring or connections.
Can I keep driving?
Avoid heavy acceleration and towing while the engine is knocking or losing power. Continued driving with a cracked cooler can worsen coolant loss and exhaust damage; arrange prompt diagnosis.
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.