P2494
DTC P2494 or P2495
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provide an overview of each diagnostic category.
DTC Descriptors
DTC P2494
- Exhaust Gas Recirculation (EGR) Cooler Bypass Position Sensor Circuit Low Voltage
DTC P2495
- Exhaust Gas Recirculation (EGR) Cooler Bypass Position Sensor Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The Engine Control Module (ECM) uses the EGR cooler bypass valve position sensor to determine the position of the bypass valve. The ECM sends a reference voltage through the 5-volt reference circuit to the position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the bypass valve position, is sent from the sensor to the ECM through the position sensor signal circuit.
Conditions for Running the DTC
* Engine speed is greater than 600 RPM for 10 s.
* The DTCs run continuously when the above conditions are met.
Conditions for Setting the DTC
P2494
The ECM detects that the EGR position sensor voltage is less than 0.25 V for greater than 5 s.
P2495
The ECM detects that the EGR position sensor voltage is greater than 4.8 V for greater than 5 s.
Action Taken When the DTC Sets
DTCs P2494 and P2495 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P2494 and P2495 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Des EGR Cooler Bypass Vlv Position and the EGR Cooler Bypass Vlv Position Sensor parameters. Command the EGR Cooler Bypass Valve from 0-100 % with a scan tool. The parameters should respond and remain within 3 % throughout the commanded range.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the Q47 EGR cooler bypass solenoid valve.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the low reference circuit terminal 3 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.
• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Ignition ON, verify that the scan tool EGR Cooler Bypass Vlv Position Sensor parameter is greater than 4.8 V.
• If the parameter is less than the specified range, test the signal circuit for a short to ground. If the circuits test normal, replace the K20 ECM.
5. Ignition ON, install a 3 A fused jumper wire between the low reference circuit terminal 3 and the signal circuit terminal 5. Verify the scan tool EGR Cooler Bypass Vlv Position Sensor parameter is less than 0.25 V.
• If the parameter is greater 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 K20 ECM.
6. If all circuits test normal, test or replace the Q47 EGR cooler bypass solenoid valve.
Component Testing
Ignition OFF, remove the Q47 EGR cooler bypass solenoid valve. Refer to Exhaust Gas Recirculation Cooler Bypass Valve Replacement (Service and Repair). Inspect the Q47 EGR cooler bypass solenoid valve for the following conditions:
* A sticking, binding or frozen EGR cooler bypass solenoid valve
* Any coking, soot build up, debris or damage that can cause the valve to stick partially open or closed
• If a condition is found, clean or replace the Q47 EGR cooler bypass solenoid valve as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Exhaust Gas Recirculation Cooler Bypass Valve Replacement (Service and Repair)
* Control Module References (Control Module References) for ECM replacement, setup and programming.