The diesel exhaust temperature sensors are thermistors and change resistance based on the temperature being measured. The Engine Control Module (ECM) provides a 5 volt reference voltage to the sensor. The ECM monitors the change in signal voltage and converts this to a temperature value.
The aftertreatment temperature sensors are used by the Electronic Control Module (ECM) to monitor the engine exhaust temperatures in the aftertreatment system. The aftertreatment temperature sensors are thermistors and change resistance based on the temperature being measured. The ECM provides a 5 volt reference voltage to the sensor. The ECM monitors the change in signal voltage and converts this to a temperature value. When the exhaust gas temperature is cold, the sensor or thermistor resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to ground. Therefore, the ECM senses a high signal voltage or low temperature. When the exhaust gas temperature is hot, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage, or a high temperature. The ECM will set the fault if it detects that the diesel oxidation catalyst inlet exhaust gas temperature sensor signal voltage is greater than a calibrated voltage (VDC) for more than a calibrated time. The ECM illuminates the MIL lamp immediately when the diagnostic runs and fails. A default value for the aftertreatment diesel oxidation catalyst inlet temperature reading will be used and active regeneration of the diesel particulate filter will be disabled. The ECM will turn off the MIL lamp immediately after the diagnostic runs and passes.
Removal & Installation
- Raise and support vehicle.
- Disconnect the diesel exhaust temperature sensor electrical connector.
Remove the diesel exhaust temperature sensor.
- Install the diesel exhaust temperature sensor.
- Connect the diesel exhaust temperature sensor electrical connector.
- Lower the vehicle.
- Disconnect the exhaust temperature sensor.
- Check connectors clean and repair as necessary.
Using an ohmmeter check the resistance of the sensor.
NOTEThe sensor's resistance value increases with decreasing temperature at 122°F-(50°C) the resistance ranges from 82k to 137k ohms.
- The resistance reading should be between 82k and 300k ohms at ambient temperature.
- If the reading was not as stated suspect faulty exhaust temperature sensor