Aftertreatment Exhaust Gas Temperature 2 – Data Valid but Above Normal Operational Range – Moderately Severe Level
|Fault Code: 1968
Aftertreatment Exhaust Gas Temperature 2 – Data Valid but Above Normal Operational Range – Moderately Severe Level. The aftertreatment diesel particulate filter inlet temperature sensor reading has exceeded the maximum temperature limit.
Active aftertreatment diesel particulate filter regeneration will be disabled.
ISX and ISM – Aftertreatment Temperature Sensors
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 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 aftertreatment diesel particulate filter inlet temperature sensor is located in the aftertreatment system. It is located at the outlet of the diesel oxidation catalyst and before the aftertreatment diesel particulate filter. Refer to the OEM service manual.
Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position and when the engine is running.
Conditions for Setting the Fault Codes
The aftertreatment diesel particulate filter inlet temperature sensor reading exceeds 649°C [1200°F] for 5 seconds and then returns below 550°C [1021°F]. This must occur five times before the fault code is logged.
Action Taken When the Fault Code is Active
- The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
- Active aftertreatment diesel particulate filter regeneration will be disabled.
- The exhaust gas recirculation (EGR) valve operation will be disabled.
Conditions for Clearing the Fault Code
The ECM will turn off the amber CHECK ENGINE light and the fault code will be set to inactive when the keyswitch is cycled.
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM. Refer to Procedure 019-032 in Section 19.
An intermittent fault code condition may be caused by the aftertreatment sensor and related wiring being shorted or damaged (melted), due to component interference. If an intermittent fault code condition exists, inspection of the aftertreatment sensors and wiring for any possible damage is required. Use the appropriate securing methods to make sure the sensor and wiring are not interfering or contacting other components.
Possible causes of this fault code include:
- A damaged fuel injector causing unburned fuel to enter the exhaust system
- A damaged aftertreatment fuel injector
- Aftertreatment diesel particulate filter inlet temperature sensor failed in-range
- Excessive engine oil being introduced into the exhaust system from the engine or turbocharger
- Aftertreatment temperature sensor has shorted and/or the sensor wiring or connector has been damaged.