SPN 105 - FMI 4 (Fault Code 154)

SPN 105 - FMI 4 (Fault Code: 154)
ISB, ISC, and ISL - Intake Manifold 1 Temperature Sensor Circuit

Fault Code: 154
PID(P), SID(S): P105
SPN: 105
FMI: 4/4

REASON: Intake Manifold 1 Temperature Sensor Circuit - Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at intake manifold air temperature circuit.

EFFECT: Possible white smoke. Fan will stay ON if controlled by ECM. No engine protection for intake manifold air temperature.

Circuit Description:
The intake manifold temperature sensor is a variable resistor sensor and is used to measure the temperature of the air entering the intake manifold of the engine. The electronic control module (ECM) supplies 5 volts to the intake manifold temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the intake manifold temperature.

Component Location:
The intake manifold air temperature sensor is located in the air intake manifold.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes:
The ECM detects that the intake manifold temperature signal voltage is less than 0.12-VDC for more than 1 second.

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 intake manifold temperature reading is used.

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.
  • The intake manifold temperature sensor shares return wires in the engine harness with other sensors. Opens and shorts in the engine harness can cause multiple fault codes to be active. Check fault codes with multiple counts first.

Possible causes of this fault code include:
• Signal circuit shorted to ground in the harness
• Signal circuit shorted to return or ground in the sensor.

Read More:
SPN 105 - FMI 3 (Fault Code 153)
SPN 110 - FMI 0 (Fault Code 151)


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