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Aftertreatment Exhaust Gas Temperature 1 Circuit – Voltage Below Normal or Shorted to Low Source
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Overview
| CODE | REASON | EFFECT |
| Fault Code: 1665 PID: S326 SPN: 3241 FMI: 4/4 LAMP: Amber SRT: |
Aftertreatment Exhaust Gas Temperature 1 Circuit – Voltage Below Normal, or Shorted to Low Source. Low signal voltage detected at the catalyst inlet sensor circuit. |
Active aftertreatment diesel particulate filter regeneration will be disabled. |
 ISX and ISM – Aftertreatment Temperature Sensors
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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 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 oxidation catalyst inlet temperature sensor is located in the aftertreatment system. It is located at the inlet of the aftertreatment catalyst. Refer to the OEM troubleshooting and repair manual.
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 oxidation catalyst inlet temperature sensor 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 oxidation catalyst inlet temperature sensor reading is used.
- Active regeneration of the aftertreatment particulate trap 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. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.
The aftertreatment diesel oxidation catalyst inlet temperature sensor shares return wires in the OEM harness with other sensors. A shorted return wire 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.
Refer to Troubleshooting Fault Code t05-1665
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