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Code 25, Intake Air Temperature High: Notes

WARNING: This page is about a different car, the 1994 GMC Sonoma and 1994 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.

ECM applies and monitors a voltage signal (4-6 volts) to MAT sensor. When manifold air is cold, sensor resistance is high and ECM sees a high signal voltage. As air warms, resistance decreases and voltage sensed by ECM drops. Sensor resistance can be measured at sensor terminals with harness disconnected.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This checks if code is a hard failure or an intermittent condition. Code 25 will set if monitored MAT sensor temperature is greater than 275°F (135°C).
  2. This simulates conditions for a Code 23. If scan tester displays a low temperature, ECM and wiring are not at fault.
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