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.
Input Components
Input components are monitored for circuit continuity and out-of-range values. This includes rationality checking. Rationality checking refers to indicating a fault when the signal from a sensor does not seem reasonable. An example of a rationality concern is a throttle position (TP) sensor that indicates high throttle position at low engine loads. Input components may include, but are not limited to, the following sensors:
- Throttle position (TP) sensor
- Engine coolant temperature (ECT) sensor
- Intake air temperature (IAT) sensor
- Crankshaft position (CKP) sensor
- Camshaft position (CMP) sensor
- Heated oxygen sensor (HO2S)
- Knock sensor (KS)
- Manifold absolute pressure (MAP) sensor
- Vehicle speed sensor (VSS)
In addition to the circuit continuity and rationality check, the ECT sensor is monitored for its ability to achieve a steady state temperature to enable closed loop fuel control.
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.