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Accurate Throttle Position in Transmission Control

The throttle position or accelerator pedal position is one of the most important inputs into the COMPUSHIFT transmission control system. It needs to be right at all times because it is used to control the shift schedule (when the transmission shifts), and the shift process (how the shift occurs). Note that some transmissions can not use the throttle position sensor as the only indication of engine torque and driver intent. These require integration to an engine management system, usually over CAN bus.

If you're installing a custom throttle position sensor or using an existing sensor, please inspect or set as described below. This goes for Diesel applications as well as gasoline, mechanical, or electronic injection. If you are making your own brackets, follow these suggestions and it will work just fine:

  • Position sensor must be linear to throttle opening.

    • At 0% throttle, TPS should be 0% to 2% of stroke.

    • At 50% throttle, TPS should be at 50% of stroke.

    • At 100% throttle, TPS should be at 100% of stroke.

  • If TPS reaches 100% before the throttle, your shift points will be late and hard. Your downshifts will be early and sensitive, and possibly there will be no 4th gear or it will fall out of 4th.

  • If TPS lags behind the throttle, your pressure and shift points will run lower than normal. This will cause early shift points and possible transmission slipping and damage.

  • When TPS is correct, all functions of shifting and pressure control will be normal. Upshifting and downshifting will function like any normal transmission.

  • If you make any changes on the TPS linkage or throttle linkage, always do a TPS recalibration on COMPUSHIFT.

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