SPN 3249 - FMI 2 (Fault Code 1676)
SPN3249 FMI2
Aftertreatment Exhaust Gas Temperature 2 - Data Erratic, Intermittent, or Incorrect
CODES:
Fault Code: 1676
PID(P), SID(S): None
SPN: 3249
FMI: 2/2
Lamp: Amber
REASON: Aftertreatment Exhaust Gas Temperature 2 - Data Erratic, Intermittent, or Incorrect. The
aftertreatment diesel particulate filter inlet temperature sensor is not changing with engine operating conditions.
EFFECT: Active aftertreatment diesel particulate filter regeneration will be disabled.
Circuit Description:
The aftertreatment temperature sensors are used by the engine 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 low, 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 high, 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.
Component Location:
The aftertreatment diesel particulate filter inlet temperature sensor is located in the aftertreatment system. It is located at the outlet of the catalyst and before the aftertreatment particulate filter. See equipment manufacturer service information.
Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running and fuel injection into the aftertreatment system is not occurring.
Conditions for Setting the Fault Codes:
The ECM detects that the aftertreatment diesel particulate filter inlet temperature sensor reading is not changing with engine operating conditions.
Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A default value for the aftertreatment diesel particulate filter inlet temperature reading is used.
• Active aftertreatment diesel particulate filter regeneration will be disabled.
Conditions for Clearing the Fault Code:
• To validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop-and-go city driving and steady-state highway driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.
• To validate the repair using a Chassis Dynamometer Test, utilize a routine that incorporates acceleration and motoring events, steady-state highway operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.
• The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
• For On-Board Diagnostics (OBD) engines, the ECM will turn off the malfunction indicator lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
• The "Reset All Faults" command in INSITE™ electronic service tool can be used to clear active and inactive fault codes, as well as extinguish the MIL for OBD applications.
Shop Talk:
Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM.
Possible causes of this fault code include:
• Stuck in-range aftertreatment diesel particulate filter inlet temperature sensor
• High resistance in the aftertreatment diesel particulate filter inlet temperature sensor SIGNAL or RETURN wires.
Read More:
SPN 3249 - FMI 4 (Fault Code 1674)
SPN 3249 - FMI 3 (Fault Code 1675)
Blog.Teknisi
Aftertreatment Exhaust Gas Temperature 2 - Data Erratic, Intermittent, or Incorrect
 |
| ISB, ISC, and ISL with CM2150 - Aftertreatment Temperature Sensors |
CODES:
Fault Code: 1676
PID(P), SID(S): None
SPN: 3249
FMI: 2/2
Lamp: Amber
REASON: Aftertreatment Exhaust Gas Temperature 2 - Data Erratic, Intermittent, or Incorrect. The
aftertreatment diesel particulate filter inlet temperature sensor is not changing with engine operating conditions.
EFFECT: Active aftertreatment diesel particulate filter regeneration will be disabled.
Circuit Description:
The aftertreatment temperature sensors are used by the engine 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 low, 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 high, 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.
Component Location:
The aftertreatment diesel particulate filter inlet temperature sensor is located in the aftertreatment system. It is located at the outlet of the catalyst and before the aftertreatment particulate filter. See equipment manufacturer service information.
Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running and fuel injection into the aftertreatment system is not occurring.
Conditions for Setting the Fault Codes:
The ECM detects that the aftertreatment diesel particulate filter inlet temperature sensor reading is not changing with engine operating conditions.
Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A default value for the aftertreatment diesel particulate filter inlet temperature reading is used.
• Active aftertreatment diesel particulate filter regeneration will be disabled.
Conditions for Clearing the Fault Code:
• To validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop-and-go city driving and steady-state highway driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.
• To validate the repair using a Chassis Dynamometer Test, utilize a routine that incorporates acceleration and motoring events, steady-state highway operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.
• The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
• For On-Board Diagnostics (OBD) engines, the ECM will turn off the malfunction indicator lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
• The "Reset All Faults" command in INSITE™ electronic service tool can be used to clear active and inactive fault codes, as well as extinguish the MIL for OBD applications.
Shop Talk:
Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM.
Possible causes of this fault code include:
• Stuck in-range aftertreatment diesel particulate filter inlet temperature sensor
• High resistance in the aftertreatment diesel particulate filter inlet temperature sensor SIGNAL or RETURN wires.
Read More:
SPN 3249 - FMI 4 (Fault Code 1674)
SPN 3249 - FMI 3 (Fault Code 1675)
Blog.Teknisi
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