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HINO P2457 FAULT CODE: EGR COOLER PERFORMANCE

21/10/2025

Technical description

The engine ECU detects abnormally high EGR gas temperatures by means of the EGR cooler outlet gas temperature sensor.

Description of malfunction

The EGR cooler efficiency has dropped.

DTC set condition

DTC Detection Condition:

Engine revolution is more than 1,500 r/min.
Fuel injection quantity ≥ 40 mm3/st. cyl.
Battery voltage is in the range of 10 V to 16 V.
Engine speed fluctuation < 156 r/min.
Fuel injection quantity fluctuation < 87 mm3/st. cyl.
Atmospheric pressure ≥ 75 kPa {10.8 psi}.
Vehicle speed ≥ 21 km/h {13 mph}.
Intake quantity ≥ 75 g/sec.
Intake temperature sensor (with built-in air flow sensor) is at least -10°C {14°F}.

The above conditions continue for at least 40 seconds.

Judgment Criteria:

The calculated EGR cooler efficiency, which is derived from the engine speed, fuel injection rate, EGR gas outlet temperature, and coolant temperature, does not exceed 65%.
And: The calculated intercooler efficiency, which is derived from the intake temperature sensor, boost pressure sensor, intake air temperature sensor (intercooler outlet), and atmospheric pressure sensor, exceed 45 – 65% (for vehicle speeds 21 and 40 km/h {13 and 25 mph}).
And: The difference among the estimated EGR quantity calculated from the engine speed and fuel injection rate, the estimated intake manifold temperature calculated from the EGR gas outlet temperature sensor and intake air temperature sensor (intercooler outlet), and the value of the intake air temperature sensor (intake manifold) are within 40oC {104oF} (when EGR quantity is 40%).

Reset condition

Just after restoration to normal condition.

Indication, warning or system control regulation when the DTC is set

MIL: ON
SVS light: OFF

Symptoms on the vehicle when the DTC is set

Symptoms on the vehicle due to malfunction:

Insufficient output or engine stall because of DPR filter clogging due to abnormal soot buildup

Pre-inspection work

Check that the battery voltage is in the normal range.

After-inspection work

Clear all past DTCs.
Check that no DTC is stored after test drive.

Possible causes

EGR cooler outlet gas temperature sensor:

Sensor failure.

Circuit supplying coolant to EGR cooler:

Coolant leakage from coolant circuit.
Air incursion due to improper air venting.

EGR cooler:

Air incursion due to improper air venting.
Coolant leakage from EGR cooler.
Deformation of EGR cooler coolant passageway.
Obstruction due to soot buildup in inlet/outlet of EGR gas passageway.
Obstruction due to buildup of foreign substances in coolant passageway of EGR cooler.

EGR valve malfunction.

Diesel throttle valve malfunction.

SCV malfunction.

Injector malfunction.

Inspection procedure

Troubleshooting steps

Step 1

Inspect the EGR cooler outlet gas temperature sensor connector.

Check the connection of the EGR cooler outlet gas temperature sensor connector (Looseness and poor contact).

Were any failures found?

Yes – Connect securely, repair if needed.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 2.

Step 2

Inspect the EGR cooler outlet gas temperature sensor.

Check the installation of the EGR cooler outlet gas temperature sensor.
Make sure there is no dirt or damage to the EGR cooler outlet gas temperature sensor.

Were any failures found?

Yes – Clean the EGR cooler outlet gas temperature sensor and install it properly.

If damaged, replace the EGR cooler outlet gas temperature sensor.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 3.

Step 3

Inspect the EGR cooler outlet gas temperature sensor unit.

Set the starter switch to the “LOCK” position.
Disconnect the EGR cooler outlet gas temperature sensor.
Use the electrical tester to measure the resistance between the terminals of the EGR cooler outlet gas temperature sensor.

MEASUREMENT CONDITIONS

TESTER

CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

EGR cooler outlet gas temperature sensor

THG – E2

20°C {68°F}: 13.7 – 29.8 kΩ

50°C {122°F}: 7.13 – 13.7 kΩ

80°C {176°F}: 4.1 – 7.13 kΩ

Do the measurements meet the standard value?

Yes – Go to Step 4.

No – Replace the EGR cooler outlet gas temperature sensor.

Clear all past DTCs. Check that no DTC is detected after test drive.

Step 4

Inspect the coolant.

Check the level and condition of the coolant in the coolant reservoir.
Check the condition of the coolant pipe (clogging or leaks).

Were any failures found?

Yes – Replenish the coolant, or repair or replace the faulty part.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 5.

Step 5

Inspect the EGR cooler 1.

Check if soot is obstructing the inlet/outlet of the EGR cooler gas passageway.

Were any failures found?

Yes – Remove the soot in the gas passageway inlet/outlet and then go to Step 6.

No – Go to Step 6.

Step 6

Inspect the EGR cooler 2.

Check if there are foreign substances stuck to the EGR cooler coolant passageway.
Check the EGR cooler coolant passageway for obstruction due to deformation or other damage.
Check if coolant is leaking from the EGR cooler.

Were any failures found?

Yes – Remove the soot in the gas passageway inlet/outlet, or repair or replace the faulty part. If the only cause of the malfunction was soot, go to Step 6.

No – Go to Step 7.

Step 7

Inspect the EGR valve.

Check the EGR valve for damage due to incursion of foreign substances.
Check if the inlet/outlet of the exhaust gas passageway is obstructed by soot.

Were any failures found?

Yes – Remove foreign substances and clean the passageway. Replace the EGR valve if it is damaged.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 8.

Step 8

Check the response delay of the EGR valve [Diagnostic Tool].

Connect the vehicle to the diagnostic tool.
Set the starter switch to the “ON” position.
Select [Engine] on the screen of the diagnostic tool.
Select [Inspection Menu] and then [EGR inspection] from the menu, then inspect the response delay at the Target EGR position and Actual EGR position.

CAUTION: Perform the inspection while the engine is stopped to avoid damages.

Inspection Procedure:

Select [Inspection Menu].
Select [EGR inspection].
Click [Start inspection].
Select [EGR opening UP]:

Inspect the response delay at each step of the Target EGR position and Actual EGR position from 0 to 100%.

Select [EGR opening DOWN]:

Inspect the response delay at each step of the Target EGR position and Actual EGR position from 100 to 0%.

NOTE: The EGR opening position changes of around 10% per step between 0 – 100%.

STANDARD VALUES

The response delay should be less than 5 seconds.

Do the measurements meet the standard value?

Yes – Go to Step 9.

No – Replace the EGR valve.

Clear all past DTCs. Check that no DTC is detected after test drive.

Step 9

Inspect the diesel throttle valve.

Stop the engine.
Check the working condition of the diesel throttle valve (abnormal opening or valve sticking).

Were any failures found?

Yes – Replace the diesel throttle valve.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 10.

Step 10

Inspect the SCV [Diagnostic Tool].

Perform an SCV test and a malfunction reproduction test.

For a detailed procedure, refer to the separate SCV Free Acceleration Test in the following pages.

Were any failures found?

Step 11

Inspect the Injector [Diagnostic Tool].

Check the injection quantity and the rotational fluctuation.

Start the Engine.
Select [Injection quantity] from the [Data monitor setting] menu and measure the fuel injection quantity.
Select [Engine revolution] from [Data monitor setting] on the menu and measure the rotational fluctuation.

MEASUREMENT CONDITIONS

Engine speed: 1,500 r/min

No-load

T/M shift lever: Neutral

A/C off and Air compressor un-operating

Engine coolant temperature: More than 80°C {176°F}

STANDARD VALUES
TYPE OF	Q (mm3/st)	⊿Ne (r/min)
MT	5.0q ≤	≤ 26
Allison 2200	6.0q ≤
Allison 2500
Allison 3500

Do the measurements meet the standard value?

(both Injection quantity and rotational fluctuation)

Yes – Go to Step 12.

No – Replace the injector.

Clear all past DTCs. Check that no DTC is detected after test drive.

Step 12

Check the DTC detected (Engine ECU) [Diagnostic Tool].

Warm-up the engine. (Engine coolant temperature: 60oC {140oF} or more).
Stop the engine.
Set the starter switch to the “ON” position.
Select [Engine] and check if P2457 has been detected.

Has DTC P2457 been detected?

Yes – Replace the engine ECU.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Procedure completed.

Clear all past DTCs. Check that no DTC is detected after test drive.

SCV free acceleration test

TEST METHOD

Engine Speed Pattern

After engine has reached operating temperature (more than 82oC {179.6oF}).
After air compressor completed building pressure.
A/C, Head lights off.
All devices off. (PTO, Refrigeration compressor, etc.).
Control the engine revolution by means of operating Cruise Control system.

Types of data to be measured by the diagnostic tool

Engine revolution.
Engine coolant temperature.
Injection quantity.
Pump current target final value.
Actual common rail pressure.
Target common rail pressure.

If the following symptoms occur, the test FAILS. If they do not occur, then test is OK.

Pressure is reduced by 5 MPa or more continually for 5 seconds or more.
Replace the supply pump.

Pressure is increased by 5 MPa or more continually for 5 seconds or more.
Replace the SCV.

The maximum common rail pressure exceeds 222 MPa for even a moment during pressure increase.
Replace the SCV.

After the maximum common rail pressure exceeds 222 MPa during pressure increase, the actual rail pressure falls below the target rail pressure.
Replace the SCV.

Before the maximum common rail pressure exceeds 222 MPa during pressure increase, the actual rail pressure falls below the target rail pressure rapidly.
Replace the common rail.