Home › Codes › SPN 105 › FMI 4

SPN 105 FMI 4

Intake Manifold #1 Temperature — Voltage below normal or shorted low.
The sensor circuit voltage is lower than it should ever be, usually near zero.

What the SPN covers: Temperature of the air entering the cylinders after the charge air cooler. More on SPN 105.

What FMI 4 usually points to: Signal wire shorted to ground, a lost 5 V reference, or an open signal wire on a pulled-down circuit. More on FMI 4.

Severity

MEDIUM — fix soon

High intake temps reduce power and can lead to a derate. Drivable with care.

Likely causes

  1. Wiring or connector fault in this circuit (most common for electrical FMIs)
  2. Dirty or blocked charge-air cooler fins
  3. Charge-air cooler leak
  4. Fan not engaging
  5. EGR cooler problem raising intake temperature
  6. Sensor or wiring fault

Checks & fixes (easiest first)

  1. Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins
  2. Check the reference voltage, ground and signal at the component per OEM pin-out
  3. Clean the CAC and radiator stack
  4. Verify fan engagement
  5. Pressure-test the CAC
  6. Compare the sensor to ambient after a cold soak

FAQ

What does SPN 105 FMI 4 mean?

Intake Manifold #1 Temperature — voltage below normal or shorted low. The sensor circuit voltage is lower than it should ever be, usually near zero.

Is SPN 105 FMI 4 serious?

High intake temps reduce power and can lead to a derate. Drivable with care.

What should I check first for SPN 105 FMI 4?

Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins; Check the reference voltage, ground and signal at the component per OEM pin-out; Clean the CAC and radiator stack.