Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPONTIAC1990FIREBIRD FORMULA, 5.0 F, AUTOMATIC, 4L60/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - V8 PFICODE 23: MAT SENSOR SIGNAL VOLT HIGHNOTES
1990 Pontiac Firebird Formula, 5.0 F, Automatic, 4L60/MD8
Code 23: Mat Sensor Signal Volt High: Notes
1990 Pontiac Firebird Formula, 5.0 F, Automatic, 4L60/MD8SECTION Notes
- Code 23 will set within 4-8 minutes if signal voltage indicates manifold air temperature is low for 3-12 seconds and no vehicle speed signal is present (vehicle not moving). Due to the conditions necessary to set a Code 23, the SERVICE ENGINE SOON light will only stay on when all conditions are met. 2) A Code 23 will set due to an open sensor, wire or connection. This test determines if the wiring and ECM are okay. The MAT sensor is difficult to reach on some models so this test can be performed at the MAT sensor harness connector. 3) This determines if an open is present in sensor signal or ground circuit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.