SPN 3241 - FMI 0 (Fault Code 1966)
SPN3241 FMI0
Aftertreatment Exhaust Gas Temperature 1 - Data Valid But Above Normal Operating Range - Most
Severe Level
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| ISB, ISC, and ISL - Aftertreatment Exhaust Gas Temperature Sensors |
Fault Code: 1966
PID(P), SID(S): 326
SPN: 3241
FMI: 0
Lamp: Red
REASON: Aftertreatment Exhaust Gas Temperature 1 - Data Valid But Above Normal Operating Range - Most Severe Level. Engine exhaust gas temperatures entering the aftertreatment system are above the engine protection limits.
EFFECT: The engine will shut down.
Circuit Description:
The aftertreatment exhaust gas temperature sensors are used by the electronic control module (ECM) to monitor the exhaust temperatures in the aftertreatment system. The aftertreatment exhaust gas 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.
Component Location:
The aftertreatment diesel oxidation catalyst inlet temperature sensor is located in the inlet section of the aftertreatment system.
The aftertreatment diesel particulate filter inlet temperature sensor is located in the aftertreatment system. It is located at the outlet of the aftertreatment diesel oxidation catalyst and before the aftertreatment diesel particulate filter.
The aftertreatment diesel particulate filter temperature outlet sensor is located in the outlet section of the aftertreatment system. Refer to the OEM service manual for the location of the vehicle aftertreatment system.
Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running and active regeneration of the aftertreatment diesel particulate filter is not occurring.
Conditions for Setting the Fault Codes:
The ECM detects one of the following:
• The aftertreatment diesel oxidation catalyst inlet temperature is greater than 617°C [1143°F] for 65 seconds.
• The aftertreatment diesel particulate filter inlet temperature is greater than 612°C [1134°F] for 100 seconds.
• The aftertreatment diesel particulate filter outlet temperature is greater than 617°C [1143°F] for 145 seconds.
• The temperature differential across the aftertreatment diesel oxidation catalyst is greater than 220°C [396°F] for 55 seconds.
• The temperature differential across the aftertreatment diesel particulate filter is greater than 265°C [477°F] for 140 seconds.
Action Taken When the Fault Code is Active:
• The ECM illuminates the red STOP ENGINE lamp immediately after the diagnostic runs and fails.
• Active and stationary (parked) regeneration will be disabled.
• Exhaust gas recirculation (EGR) valve operation will be disabled.
• Engine shutdown will occur 30 seconds after the fault becomes active. In all calibrations except for emergency vehicle calibrations, engine shutdown will occur after 30 seconds if engine protection shutdown is enabled or disabled. Engine shutdown will not occur in emergency vehicle calibrations.
Conditions for Clearing the Fault Code:
The ECM will turn off the red STOP ENGINE lamp and the fault code will be set to inactive when the temperatures in the aftertreatment system drop below the temperature values listed:
• The aftertreatment diesel oxidation catalyst inlet temperature is less than 592°C [1098°F].
• The aftertreatment diesel particulate filter inlet temperature is less than 587°C [1089°F].
• The aftertreatment diesel particulate filter outlet temperature is less than 592°C [1098°F].
• The temperature differential across the aftertreatment diesel oxidation catalyst is less than 195°C [351°F].
• The temperature differential across the aftertreatment diesel particulate filter is less than 240°C [432°F].
The fault code will also be set inactive following a key cycle.
Shop Talk:
This fault code is logged when the ECM has detected a high temperature condition in the aftertreatment system and active regeneration of the aftertreatment diesel particulate filter is not occurring. The fault code indicates that a secondary fuel source is entering the aftertreatment system and is creating a temperature increase across the aftertreatment diesel oxidation catalyst and/or aftertreatment diesel particulate filter.
Possible causes of this fault code include:
• Excessive engine oil or diesel fuel being introduced into the exhaust system from the engine
• A damaged engine fuel injector causing unburned diesel fuel to enter the exhaust system
• The aftertreatment diesel oxidation catalyst inlet temperature sensor failed in-range
• The aftertreatment diesel particulate filter inlet temperature sensor failed in-range
• The aftertreatment diesel particulate filter outlet temperature sensor failed in-range
• An in-range engine sensor malfunction has occurred, causing excessive fuel to enter the exhaust system.
The aftertreatment system must be inspected after making the appropriate repair outlined in this fault code troubleshooting tree. Progressive damage to the aftertreatment system may have occurred. Remove the exhaust aftertreatment system from the vehicle to inspect it for potential damage and reuse.
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