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 P027, Open Throttle Position Switch Signal: Notes
Diagnostic test monitors ISC throttle position switch during some coast down and idle conditions with throttle position switch open and brake applied. Under these conditions, PCM commands ISC to retract, and monitors TP sensor for corresponding decrease in throttle position. PCM sets Code P027 if it detects a decrease in throttle position 2 times in succession, throttle is resting on ISC plunger and throttle position switch should be closed.
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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.