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.
Pcm Code EO26, Shorted Throttle Switch Circuit: Action
PCM turns on SERVICE ENGINE SOON light and assumes closed throttle if brakes are applied or TPS position is less than or equal to 18 degrees. PCM also assumes open throttle when brakes are off or TPS position is more than 18 degrees.
The throttle switch is part of ISC motor assembly. The PCM provides a 5-volt reference signal on circuit No. 427. When throttle lever contacts ISC plunger, throttle switch closes. When throttle switch is closed, input voltage is low. Code EO26 sets when PCM sees a TPS signal greater that 20 degrees (accelerator applied) but the throttle switch remains closed.
- Code EO26 can be caused by a sticking or binding TPS.
- Check ISC harness for opens or shorts to ground or voltage and check ISC adjustment. If ISC is adjusted properly and no shorts or opens are present in harness, replace ISC motor.
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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.