GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2007 🢒 Isuzu MD F-Series 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LF8) 🢒 DTC P2457

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor

DTC P2457: Exhaust Gas Recirculation (EGR) Cooling System Performance

Circuit/System Description

The exhaust gas recirculation (EGR) cooler exhaust gas temperature sensor is a variable resistor. The EGR cooler exhaust gas temperature sensor has a signal circuit and a low reference circuit. The EGR cooler exhaust gas temperature sensor measures the temperature of the EGR cooler exhaust gas temperature. The engine control module (ECM) supplies 5 volts to the EGR cooler exhaust gas temperature signal circuit and a ground for the EGR cooler exhaust gas temperature low reference circuit. When the EGR cooler exhaust gas temperature sensor is cold, the sensor resistance is high. When the EGR cooler exhaust gas temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the EGR cooler exhaust gas temperature signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the EGR cooler exhaust gas temperature signal circuit. If the EGR cooler exhaust gas temperature does not increase normally, or does not reach the regulating temperature of the EGR cooler, the engine is considered not warm enough for stable low emission operation. Additionally other diagnostics that use the EGR cooler exhaust gas temperature as enabling criteria, may not run when expected.

Conditions for Running the DTC
    • DTCs P0182, P0183, P0237, P0238, P0409, P040C, P040D, P041C, P041D, P0506, P0507, P0642, P0643, P0652, P0653, P2228, and P2229 are not set.
    • The exhaust brake control is commanded OFF.
    • The DPF status is not in regeneration
    • The intake throttle position is less than 3 percent.
    • The diesel particulate filter differential pressure is between -10 and +20 kPa.
    • The VNT mode is Normal.
    • The following conditions are met for 10 seconds:
       - The battery voltage is between 10-16 volts.
       - The ignition switch is ON for longer than 2 seconds.
       - EGR position is more than 30 percent.
       - Engine speed is more than 1000 RPM.

Conditions for Setting the DTC

The ECM detects that the exhaust temperature, catalyst temperature, is error.

Action Taken When the DTC Sets

DTC P2457 is a Type B DTC.

Conditions for Clearing the DTC

DTC P2457 is a Type B DTC.

Diagnostic Aids

Inspect for any recent engine mechanical repairs. An incorrectly installed EGR cooler exhaust gas temperature sensor will cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Component Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Verify the integrity of the EGT sensor by inspecting for the following conditions:

    • Damaged components
    • Loose or improper installation

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF, disconnect the harness connector at the EGR cooler exhaust gas temperature sensor.
  2. Ignition OFF, using a DMM, measure the voltage between the signal circuit and a low reference circuit.
    3. ⇒If less than 4.8 volts, test the low reference for an open/high resistance.
  3. Ignition ON, verify the scan tool EGR cooler exhaust gas temperature parameter is more than 950°C (1742°F).
    4. ⇒If greater than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the ECM.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool EGR cooler exhaust gas temperature parameter is less than 0°C (32°F).
    5. ⇒If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  5. If all circuits test normal, replace the appropriate EGR cooler temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Exhaust Gas Recirculation Cooler Temperature Sensor Replacement - Position 1
    •  Exhaust Gas Recirculation Cooler Temperature Sensor Replacement - Position 2
    •  Control Module References for ECM replacement, setup, and programming