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.
Code 23B - Mat Circuit (High Temperature Indicated): Notes
Manifold Air Temperature (MAT) sensor uses a thermistor to control signal to ECM. ECM applies 4-6 volts to circuit No. D7 of sensor. When manifold air is cold, sensor resistance is high and ECM will see a MAT signal. As air warms, sensor resistance is low and MAT signal drops.
- Code 23B will set if engine has been running for longer than 3 minutes and a MAT temperature greater than 302°F (150°C) is detected.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.