OBD-II Diagnostic Trouble Code
P2457 — Exhaust Gas Recirculation Cooler Efficiency Below Threshold (Bank 1)
The ECM compared exhaust gas temperature before and after the EGR cooler, or the intake temperature after EGR mixing, and found the cooler is not removing enough heat. Usually this is a fouled or restricted cooler, or a coolant flow problem. Some OEMs word this code as EGR cooling system performance, but the meaning is similar.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Exhaust Gas Recirculation Cooler Efficiency Below Threshold (Bank 1)
Code
P2457
Category
Powertrain
Subsystem
Emissions
Truck-relevant
Yes
What this means for truckers
P2457 (EGR Cooler Efficiency Below Threshold) — the EGR cooler isn't reducing exhaust temp enough before recirculation. Common cause: clogged cooler core (carbon buildup) or coolant leak inside cooler. EGR cooler replacement is expensive ($2,000-4,000 on heavy-duty diesels) — clean first if possible.
Before you replace parts — try this first
P2457 on the Emissions system is most often egr cooler fouled with soot or lacquer on the gas side — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
The check-engine light comes on, with possibly high intake manifold temperature, reduced power, a derate and higher NOx. Heavy soot fouling may also cause more frequent DPF regens. If the cooler is leaking internally, coolant loss and white smoke may appear.
Common causes
- CommonEGR cooler fouled with soot or lacquer on the gas side ($1200–$4000)
- OccasionalLow coolant flow through the cooler from a weak water pump, low coolant, air in the system or a plugged coolant passage ($200–$1500)
- OccasionalFaulty EGR temperature sensor reading wrong ($120–$400)
- OccasionalEGR cooler bypass valve stuck in bypass ($300–$1000)
How to fix
Compare the EGR temperature sensors at a cold soak, and verify coolant level and that there is no air in the system
When to use: First step
Check the bypass valve operation where equipped
When to use: When the engine has an EGR cooler bypass
Remove the EGR cooler, inspect it for soot fouling, and pressure test it for internal leaks; clean or replace it
When to use: When the sensors and coolant flow are good
Address the source of excess soot, such as injectors or EGR valve sticking
When to use: When the cooler fouls repeatedly
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P244A — Diesel Particulate Filter Differential Pressure Too Low
- → P244B — Diesel Particulate Filter Differential Pressure Too High
- → P244C — Exhaust Gas Temperature Too Low Bank 1
- → P244D — Exhaust Gas Temperature Too High Bank 1
- → P245A — EGR Cooler Bypass Control Circuit/Open
Frequently Asked Questions
Can I drive with code P2457?
P2457 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P2457 on a commercial truck?
Total repair cost ranges $120–$4000 depending on the root cause. The cheapest fix is usually the first one listed below — EGR cooler fouled with soot or lacquer on the gas side — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P2457 fail a DOT inspection?
Yes — P2457 is an emissions-related code, and DOT inspectors check emissions compliance. An active emissions code with a check engine light can result in an out-of-service violation under FMCSA Part 393. The truck typically can't be moved until the code is cleared. Repeated emissions violations escalate to CSA scores.
What's the difference between P2457 and related codes?
P2457 is closely related to: P244A (Diesel Particulate Filter Differential Pressure Too Low), P244B (Diesel Particulate Filter Differential Pressure Too High), P244C (Exhaust Gas Temperature Too Low Bank 1), P244D (Exhaust Gas Temperature Too High Bank 1). These codes share the same subsystem (emissions) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P2457 is set without the companions, the issue is more isolated.
How do I prevent P2457 from coming back after a repair?
For P2457 (Exhaust Gas Recirculation Cooler Efficiency Below Threshold (Bank 1)), prevention centers on the emissions system. Keep up with PM on the EGR system — clean the valve at 200K miles. Use OEM-spec air filters. Don't ignore minor codes; they often escalate into bigger emissions failures.