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Clean the ISB diesel engine Intake Air Temperature (IAT) sensor

IAT Sensor Cleaning
1998-2002 24V diesel engine

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The IAT sensor measures the temperature of the intake nmanifold. The ECM uses this sensor reading to set injection timing and adjust the air-fuel ratio. If the fuel mileage and power output of you engine seem low, some owners have found improvement in EGT, fuel economy, and power after cleaning carbon from the IAT sensor in at the rear of the intage manifold. Engine with exhaust brakes are particularly prone to IAT sensor fouling because soot is blown back into the intake during valve overlap. Smokingdiesel.com has an information page about problems caused by the IAT sensor.

The only tool you need is a 3/8" ratchet with a 6" extension and 13/16" socket.

View of IAT from above battery Closer view of the IAT sensor The IAT sensor is found on the driver's side of the engine, almost at the back of the intake manifold.
Photo, from above the battery, of the wrench on the IAT sensor photo, from above the brake master cylinder, of the wrench on the IAT sensor Unplug the electrical connector from the sensor. You will need to spread the connect tab away from the sensor body to unplug the sensor. After the connector has been removed, use a 13/16" deep well socket, 6" extension, and ratchet to unscrew the sensor from the manifold.
Photo of a dirty IAT sensor The sensor on the left had 20,000 miles on it, and it was covered with soot. After a shot of carburator cleaner, you can see the sensor element inside the cage. Screw the clean IAT sensor back into the manifold, torque it to 10 ft-lb, and reattach the connector. Photo of a clean IAT sensor

Normal IAT Sensor resistance values:

Temperature   Resistance
  30° 40K
  32° 30k to 36k ohms
  76° 13K ohms
  77° 9k to 11k ohms
  81° 6.87K ohms
122° 3k to 4k ohms
130° 4K ohms
167 600 to 675 ohms
212 600 to 675 ohms

Replacement Sensor:

Cummins PN 3408345,    around $28.

Dodge PN 05014197AA   Sensor, Temperature (SEN, TEM),     around $18.


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Last update to this page: March 28, 2002