Code 23 & 25 (MAT)
- Clear codes. Start engine and run for one minute or until light comes on. Turn engine off and turn ignition on. Note codes.
- If code 23 is present, disconnect MAT sensor harness. Turn ignition on and check voltage between MAT sensor harness terminals. If voltage is below 4 volts, check voltage between MAT Black/Yellow harness connector and ground.
- If voltage check is below 4 volts, check for open in harness, faulty connection or ECM. If voltage in Black/Yellow wire is over 4 volts, check for faulty circuit in Red/Black wire to ECM harness connector A11.
- If reading across harness terminals in step 2) was over 4 volts, check resistance across MAT sensor terminals. See MAT SENSOR RESISTANCE table. If resistance values are not approximately as indicated, replace MAT sensor.
MAT SENSOR RESISTANCE
| Temperature | Ohms |
|---|---|
| -4°F (-20°C) | 28,677 |
| 32°F (0°C) | 9423 |
| 68°F (20°C) | 3515 |
| 104°F (40°C) | 1459 |
| 140°F (60°C) | 667 |
| 176°F (80°C) | 332 |
| 212°F (100°C) | 177 |