PACCAR PX-8 CM2150 (2007-09) Fault Code: 1665 PID: SPN: 3241 FMI: 4 Aftertreatment Exhaust Gas Temperature 1 Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the catalyst inlet sensor circuit.

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.

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:

1)Signal shorted to ground in the harness
2)Signal shorted to return or ground in the sensor.

Possible repairs:

1)Replace the aftertreatment diesel oxidation catalyst inlet temperature sensor.
2)The removal and installation of the connector may correct the fault.
3)Replace the ECM.
4)Replace the OEM harness.
5)Replace the aftertreatment harness.
6)Replace all interconnects.