Cliff: Created page with "'''Manifold air temperature sensor''' refers to the air-temperature sensor used by the Pontiac Fiero ECM. The manifold air temperature sensor tells the ECM the temperature of the incoming air. The ECM uses this information for fuel-mixture calculations, warm-up behavior, drivability control, and diagnostic trouble code decisions. == Overview == The manifold air temperature sensor is often abbreviated as MAT sensor. Air temperature affects air density. Cooler..."

2026-07-06T20:29:40Z

Created page with "'''Manifold air temperature sensor''' refers to the air-temperature sensor used by the Pontiac Fiero ECM. The manifold air temperature sensor tells the ECM the temperature of the incoming air. The ECM uses this information for fuel-mixture calculations, warm-up behavior, drivability control, and diagnostic trouble code decisions. == Overview == The manifold air temperature sensor is often abbreviated as MAT sensor. Air temperature affects air density. Cooler..."

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'''Manifold air temperature sensor''' refers to the air-temperature sensor used by the [[Pontiac Fiero]] [[ECM]].

The manifold air temperature sensor tells the ECM the temperature of the incoming air. The ECM uses this information for fuel-mixture calculations, warm-up behavior, drivability control, and diagnostic trouble code decisions.

== Overview ==

The manifold air temperature sensor is often abbreviated as MAT sensor.

Air temperature affects air density. Cooler air is denser, while warmer air is less dense. The ECM uses the MAT sensor signal along with other sensor inputs to help calculate the correct amount of fuel.

A faulty, disconnected, poorly connected, or incorrectly reading MAT sensor can cause drivability problems and may set diagnostic trouble codes.

== Location ==

{{Image wanted|Photo or diagram showing the manifold air temperature sensor location. Ideally include both the 2.8L V6 and 2.5L four-cylinder locations if different.}}

The MAT sensor location depends on the engine and year.

On the 2.8L V6, the MAT sensor is located in the air intake system so it can measure incoming air temperature before the air enters the engine.

On the 2.5L four-cylinder, the MAT sensor is also located where it can measure intake air temperature, though the exact location and appearance may vary by year and engine configuration.

The MAT sensor should not be confused with the [[Coolant temperature sensor]]. The MAT sensor measures incoming air temperature, while the coolant temperature sensor measures engine coolant temperature for the ECM.

== Sensor operation ==

The MAT sensor is a temperature-sensitive resistor. Its resistance changes as air temperature changes.

In general:

* Cold air produces a high-resistance signal.
* Hot air produces a low-resistance signal.

The ECM interprets this signal as intake air temperature.

== Related trouble codes ==

Manifold-air-temperature-sensor-related diagnostic trouble codes include:

* [[Code 23]] - Manifold air temperature sensor circuit, low temperature indication
* [[Code 25]] - Manifold air temperature sensor circuit, high temperature indication

== Code 23 ==

[[Code 23]] indicates that the ECM is seeing a MAT sensor signal that represents an unusually low air temperature reading.

Possible causes include:

* Disconnected MAT sensor
* Faulty MAT sensor
* MAT sensor wiring problem
* Poor connector contact
* Open circuit in the sensor wiring
* ECM input problem

== Code 25 ==

[[Code 25]] indicates that the ECM is seeing a MAT sensor signal that represents an unusually high air temperature reading.

Possible causes include:

* Faulty MAT sensor
* MAT sensor wiring problem
* Poor connector contact
* Short to ground in the sensor circuit
* ECM input problem
* Heat-related wiring or connector damage

== Symptoms ==

Possible symptoms of a MAT sensor or MAT circuit problem include:

* Check engine light
* Poor fuel economy
* Rich running
* Lean running
* Rough idle
* Hesitation
* Poor drivability
* Hard starting in some conditions
* Little or no obvious drivability problem

== Diagnosis ==

Basic diagnostic checks include:

# Check for stored diagnostic trouble codes.
# Inspect the MAT sensor connector.
# Check whether the sensor is disconnected.
# Inspect the sensor wiring for damage.
# Check for corrosion or poor contact at the connector.
# Test sensor resistance if equipment and temperature-reference information are available.
# Compare ECM air-temperature data through [[ALDL diagnostics]] if live data is available.
# Check ECM connector condition if the sensor and wiring appear correct.

== ALDL data ==

Live ECM data through [[ALDL diagnostics]] can be useful when diagnosing MAT sensor problems.

If the ECM reports an intake air temperature that is obviously impossible, the sensor circuit should be checked. This can help separate an actual temperature condition from a sensor, connector, wiring, or ECM input problem.

== Relationship to fuel mixture ==

The MAT sensor is one of several inputs used by the ECM to calculate fuel delivery.

Related inputs include:

* [[Coolant temperature sensor]]
* [[Manifold absolute pressure sensor]]
* [[Throttle position sensor]]
* [[Oxygen sensor]]

A wrong MAT signal can affect fuel calculations, but it should be diagnosed together with other sensor readings and trouble codes.

== Notes ==

A MAT sensor trouble code does not automatically mean the sensor itself has failed.

Wiring faults, poor connectors, open circuits, short circuits, ECM input problems, and actual unusual intake-air conditions can all cause MAT-related codes.

== See also ==

* [[Diagnostic trouble codes]]
* [[ALDL diagnostics]]
* [[ECM]]
* [[Fuel system]]
* [[Coolant temperature sensor]]
* [[Manifold absolute pressure sensor]]
* [[Code 23]]
* [[Code 25]]

[[Category:Fieropedia]]
[[Category:Diagnostics]]
[[Category:Electrical system]]
[[Category:Engine]]
[[Category:Fuel system]]

Manifold air temperature sensor - Revision history