Code 25
Code 25 is a diagnostic trouble code related to the Manifold air temperature sensor circuit on the Pontiac Fiero.
Code 25 indicates that the ECM is seeing a manifold air temperature sensor signal that represents an unusually high air temperature reading.
Overview
The manifold air temperature sensor, often abbreviated as MAT sensor, tells the ECM the temperature of the incoming air.
The ECM uses this information for fuel mixture calculations. If the ECM detects a manifold air temperature reading that is unusually high, it may set Code 25.
This can be caused by a faulty MAT sensor, wiring problem, connector problem, short to ground, or ECM input problem.
Flash pattern
Code 25 is displayed as:
- Two flashes
- Pause
- Five flashes
This represents code 25.
Animated flash pattern:
Meaning
Code 25 usually indicates that the ECM sees the MAT sensor circuit as reading too hot.
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 may include:
- Check engine light
- Poor fuel economy
- Lean or rich running depending on conditions
- Rough idle
- Hesitation
- Poor drivability
- Little or no obvious drivability problem
Diagnosis
Basic diagnostic checks include:
- Confirm that Code 25 is present.
- Inspect the MAT sensor connector.
- Inspect the sensor wiring for damage.
- Check for corrosion or poor contact at the connector.
- Check for wiring shorted to ground.
- Check for other stored trouble codes.
- Test the MAT sensor resistance if equipment is available.
- Check ECM connector condition if the sensor and wiring appear correct.
Related codes
Related MAT sensor codes include:
- Code 23 - Manifold air temperature sensor circuit, low temperature indication
Notes
Code 25 does not usually mean the incoming air is actually extremely hot. It means the ECM is receiving a signal that appears too hot.
The MAT sensor and its wiring should be checked before replacing the sensor. Poor connections, damaged wiring, or a shorted circuit can cause the same code.