SPN 3249 - FMI 4 (Fault Code 1674)
SPN3249 FMI4
Aftertreatment Exhaust Gas Temperature 2 Circuit - Voltage Below Normal or Shorted to Low Source
CODES:
Fault Code: 1674
PID(P), SID(S): None
SPN: 3249
FMI: 4/4
Lamp: Amber
REASON: Aftertreatment Exhaust Gas Temperature 2 Circuit - Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the aftertreatment diesel particulate filter inlet temperature sensor circuit.
EFFECT: Active aftertreatment diesel particulate filter regeneration will be disabled.
Circuit Description:
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 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 or thermistor 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.
Conditions for Running the Diagnostics:
This diagnostic runs continuously following a calibratible warm-up period. The diagnostic will not run for a calibratible period of time (up to 5 minutes) following a key cycle.
Conditions for Setting the Fault Codes:
The ECM detects that the aftertreatment diesel particulate filter inlet temperature signal voltage is less than 0.1-VDC for more than 2 seconds.
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 regeneration of the aftertreatment diesel particulate filter is disabled.
Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes. The ECM detects that the aftertreatment diesel oxidation catalyst inlet temperature sensor signal voltage has returned to normal operating conditions for more than 4 seconds.
Shop Talk:
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.
The aftertreatment diesel particulate filter inlet temperature sensor shares return wires in the OEM harness with other sensors. A shorted return can cause multiple fault codes to be active.
Possible causes of this fault code include:
• Signal shorted to ground in the harness
• Signal shorted to return or ground in the sensor.
Read More:
SPN 3241 - FMI 3 (Fault Code 1666)
SPN 3241 - FMI 2 (Fault Code 1667)
Blog.Teknisi
Aftertreatment Exhaust Gas Temperature 2 Circuit - Voltage Below Normal or Shorted to Low Source
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| ISB, ISC, and ISL with CM2150 - Aftertreatment Temperature Sensors |
CODES:
Fault Code: 1674
PID(P), SID(S): None
SPN: 3249
FMI: 4/4
Lamp: Amber
REASON: Aftertreatment Exhaust Gas Temperature 2 Circuit - Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the aftertreatment diesel particulate filter inlet temperature sensor circuit.
EFFECT: Active aftertreatment diesel particulate filter regeneration will be disabled.
Circuit Description:
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 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 or thermistor 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.
Conditions for Running the Diagnostics:
This diagnostic runs continuously following a calibratible warm-up period. The diagnostic will not run for a calibratible period of time (up to 5 minutes) following a key cycle.
Conditions for Setting the Fault Codes:
The ECM detects that the aftertreatment diesel particulate filter inlet temperature signal voltage is less than 0.1-VDC for more than 2 seconds.
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 regeneration of the aftertreatment diesel particulate filter is disabled.
Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes. The ECM detects that the aftertreatment diesel oxidation catalyst inlet temperature sensor signal voltage has returned to normal operating conditions for more than 4 seconds.
Shop Talk:
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.
The aftertreatment diesel particulate filter inlet temperature sensor shares return wires in the OEM harness with other sensors. A shorted return can cause multiple fault codes to be active.
Possible causes of this fault code include:
• Signal shorted to ground in the harness
• Signal shorted to return or ground in the sensor.
Read More:
SPN 3241 - FMI 3 (Fault Code 1666)
SPN 3241 - FMI 2 (Fault Code 1667)
Blog.Teknisi
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