Ford Escort/Lynx 1981-1990 Repair Guide

Air Charge Temperature Sensor



The Air Charge Temperature (ACT) sensor measures the intake air temperature or manifold air temperature. As the air temperature becomes colder, the sensor signals the air temperature change to the Powertrain Control Module (PCM). The PCM then increases fuel injector pulse width, increases cold-enrichment fuel flow, and can also advance the ignition timing, as necessary.


See Figures 1 and 2

  1. Unplug the sensor electrical connection.
  3. Using a Digital Volt Ohmmeter (DVOM) set on the resistance scale, measure across the sensor terminals.
  5. If the readings are not within the temperature versus resistance specifications shown in the accompanying chart, replace the sensor.

Click image to see an enlarged view

Fig. Fig. 1: Measure the resistance across the ACT sensor terminals and compare your readings to the temperature versus resistance values in the accompanying chart

Click image to see an enlarged view

Fig. Fig. 2: Temperature versus resistance chart-ECM systems