P2457🔧 Exhaust gas recirculation (EGR cooler, mostly diesel engines)Drive with caution, fix soon

P2457: EGR Cooling System Performance (Meaning, Causes, Fixes)

Reviewed 2026-10-24 · Based on 2 cited source(s)

What P2457 means

The EGR system sends a small amount of exhaust back into the intake to lower nitrogen oxide (NOx) emissions. On engines with an EGR cooler, engine coolant flows around tubes that carry the exhaust so the gas is cooled before it reaches the EGR valve. OBD-Codes.com says EGR coolers are found mainly on diesel engines. An EGR temperature sensor near the EGR valve tells the engine computer how hot the recirculated gas is. According to OBD-Codes.com, the computer compares that reading with an exhaust temperature sensor further down the exhaust, and sets P2457 if the EGR temperature is out of range or not clearly lower than the exhaust temperature. RepairPal describes it more simply: the computer watches the EGR cooler outlet temperature, and if the gas there is too hot, it decides the cooler isn't working and stores P2457.

Severity: can I keep driving?

Drive with caution, fix soon

The sources disagree on how urgent this is. RepairPal rates P2457 as Urgent, while OBD-Codes.com says it is an emissions code and not urgent. Because a failing EGR cooler can go along with coolant leaks or engine overheating, check your coolant level and temperature gauge right away and get it diagnosed soon rather than ignoring it.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. A clogged EGR cooler (OBD-Codes.com, RepairPal)
  2. Low engine coolant or a coolant system leak (OBD-Codes.com, RepairPal)
  3. A failed EGR temperature sensor (OBD-Codes.com, RepairPal)
  4. A faulty exhaust temperature sensor (OBD-Codes.com)
  5. Exhaust leaks (OBD-Codes.com)
  6. Engine overheating (OBD-Codes.com)
  7. Exhaust back pressure from a restricted diesel particulate filter (DPF), aftermarket exhaust parts, or an EGR block-off kit (OBD-Codes.com diagnostic notes)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Check the coolant level with the engine cold and look for leaks or signs of overheating. Low coolant is one of the listed causes.
  2. Read all stored codes and freeze frame data. OBD-Codes.com advises fixing any DPF codes before working on P2457.
  3. Check for technical service bulletins for your vehicle, since some EGR cooler problems are known issues with a set fix.
  4. Inspect the wiring and connectors for the EGR temperature sensor and exhaust temperature sensor, especially where they run near hot exhaust parts.
  5. With a scan tool, watch the EGR and exhaust temperature readings to see whether the cooler is actually lowering the gas temperature. OBD-Codes.com also uses an infrared thermometer at the cooler inlet and outlet, compared with the manufacturer's specs.
  6. If the EGR temperature reading is erratic, test the sensor and its circuit against the service manual before replacing the cooler.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • Coolant is disappearing with no visible leak, or the engine is overheating
  • You see white exhaust smoke or coolant in the oil, which needs professional diagnosis
  • The EGR cooler needs to come off, which is a big job on many diesel engines
  • You don't have a scan tool that shows EGR and exhaust temperatures

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P2457 serious?

The sources disagree. RepairPal rates it Urgent, while OBD-Codes.com calls it an emissions code that isn't urgent. Since coolant loss and overheating are possible causes, check your coolant and temperature gauge and get it looked at soon.

Does P2457 only happen on diesels?

Mostly. OBD-Codes.com says EGR coolers are, to its author's knowledge, used mainly on diesel engines, so that's where P2457 usually shows up.

Is it always the EGR cooler?

No. Both sources also list a failed EGR temperature sensor and coolant problems, and OBD-Codes.com adds exhaust leaks, the exhaust temperature sensor and DPF back pressure. Check the cheaper items before replacing the cooler.

Can an EGR delete or block-off cause P2457?

Yes. OBD-Codes.com notes that an EGR block-off kit or aftermarket exhaust parts can cause this code to be stored.

How much does it cost to fix P2457?

Neither source gives a repair cost. It ranges from a sensor to a full EGR cooler replacement, so get a written estimate after diagnosis.

Sources

  1. OBD-Codes.com: P2457 Exhaust Gas Recirculation Cooling System Performance (Stephen Darby, ASE)
  2. RepairPal: P2457 Exhaust Gas Recirculation Cooling System Performance (rated Urgent)

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.