Overview
| CODE | REASON | EFFECT |
| Fault Code: 7935 PID: SPN: 412 FMI: 10/10 LAMP: Amber SRT: |
The EGR temperature sensor is reading an erratic value at initial key ON or while the engine is running.
|
Possible reduced engine performance. |
Circuit Description
The exhaust gas recirculation (EGR) temperature sensor is a variable resistor sensor and is used to measure the temperature of the EGR gas flow after it exits the EGR cooler. The engine control module (ECM) supplies 5 volts to the EGR temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the EGR flow temperature.
The EGR temperature value is used by the ECM for the engine protection system and engine emissions control.
Component Location
The EGR temperature sensor is located on the EGR connection tube between the EGR cooler and the air intake connection.
Conditions for Running the Diagnostics
The engine must be turned OFF for period of 8 hours before this diagnostic will run. This diagnostic runs when the keyswitch is turned to the ON position after an 8 hour cold soak.
Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the EGR temperature reading was higher or lower than the other temperature sensors on the engine after an extended period of engine off time.
Action Taken When the Fault Code is Active
- The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
- Diesel exhaust fluid injection into the aftertreatment system is disabled.
- Active and stationary regeneration of the diesel particulate filter will be disabled.
- Exhaust gas recirculation (EGR) valve operation will be disabled.
- Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
Conditions for Clearing the Fault Code
- To validate the repair, the engine must be shut down with the keyswitch in the OFF position for 8 hours. After the 8 hour cold soak turn the keyswitch to the ON position for 30 seconds.
- The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
- The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
- For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
- The “Reset All Faults” command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.
Shop Talk
Possible causes of this fault code include:
Stuck in-range EGR temperature sensor
High resistance in the EGR temperature sensor signal or return wires.
Troubleshooting Summary
Solution: S00000155
Verification
Conditions
- Turn keyswitch ON.
- Connect the recommended Cummins® electronic service tool or equivalent.
Action
- Use the recommended Cummins® electronic service tool or equivalent to read the fault codes.
Specification
Before troubleshooting this fault code, troubleshoot any fault code that is active or has more than one inactive count within the last 25 engine operating hours from the following list:
- Exhaust gas temperature: 2375, 2376
Linked Solutions
- None
Repair
- Perform a search on the appropriate fault codes.
Validation
- None
Solution: S00005089
Verification
Conditions
- Turn keyswitch OFF.
- Disconnect the EGR temperature sensor from the engine wiring harness.
- Disconnect the engine wiring harness connector from the ECM.
Action
- Inspect the pins and connectors for damage.
- Measure the resistance between the EGR temperature sensor SIGNAL pin at the EGR temperature sensor engine wiring harness connector and the EGR temperature sensor SIGNAL pin at the engine wiring harness ECM connector.
- Measure the resistance between the EGR temperature sensor RETURN pin at the EGR temperature sensor engine wiring harness connector and the EGR temperature sensor RETURN pin at the engine wiring harness ECM connector.
- Refer to the circuit diagram or wiring diagram for connector pin identification.
Specification
- A malfunctioning engine wiring harness has been detected if the resistance is greater than the following specification: 10 Ω
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00005090
Verification
Conditions
- Turn keyswitch OFF.
- Disconnect the EGR temperature sensor from the engine wiring harness.
- Disconnect the engine wiring harness connector from the ECM.
Action
- Inspect the pins and connectors for damage.
- Measure the resistance between the EGR temperature sensor SIGNAL pin at the engine wiring harness ECM connector and ground.
- Refer to the circuit diagram or wiring diagram for connector pin identification.
Specification
- A malfunctioning engine wiring harness has been detected if the resistance is less than the following specification: 100k Ω
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00005079
Verification
Conditions
- Turn keyswitch OFF.
- Disconnect the EGR temperature sensor from the engine wiring harness.
- Disconnect the engine wiring harness connector from the ECM.
Action
- Inspect the pins and connectors for damage.
- Measure the resistance between the EGR temperature sensor SIGNAL pin at the engine wiring harness ECM connector and all other pins in that connector.
- Measure the resistance between the EGR temperature sensor RETURN pin at the engine wiring harness ECM connector and all other pins in that connector.
- Refer to the circuit diagram or wiring diagram for connector pin identification.
Specification
- A malfunctioning engine wiring harness has been detected if the resistance is less than the following specification: 100k Ω
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00000443
Verification
Conditions
- Connect all components.
- Turn keyswitch ON.
- Connect the recommended Cummins® electronic service tool or equivalent.
Action
- Use the recommended Cummins® electronic service tool or equivalent to read the fault codes.
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revision listed in the ECM calibration revision history for applicable changes.
Specification
- If a calibration update for this fault code is available, the ECM calibration revision must be that revision or higher.
Linked Solutions
- None
Repair
- Prior to downloading the ECM calibration, check to see that all job images and all other troubleshooting has been documented as downloading an ECM calibration will remove the fault codes on the ECM.
- Download the updated ECM calibration code.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
If all steps have been completed and no root cause has been identified, then follow the technical escalation process.