Throttle Position when there are two sensors?

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l8apex
Posts: 5
Joined: Sat Mar 07, 2020 4:05 pm

Throttle Position when there are two sensors?

Post by l8apex »

My engine is drive-by-wire. The throttle body contains two separate TP sensors.

Direct from the manual:
There are 2 individual TP sensors within the throttle body assembly.

The TP sensors are used to determine the throttle plate angle. The TP sensors provide the engine control module (ECM) with a signal voltage proportional to throttle plate movement. The TP sensor 1 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. The TP sensor 2 signal voltage at closed throttle is near the low reference and increases as the throttle plate is opened.
TPS 1 decreases in voltage.
TPS 2 increases in voltage.

Does it matter which I tap into so long as I know the voltage range? Is there a preference?

Also, there is an Accelerator Pedal Position sensor. Would that also work as a TPS reference for RaceCapture? It'd make wiring easier. It has 2 sensors, but they both increase in voltage.

indianapolis77
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Joined: Sun Mar 22, 2020 8:43 am

Post by indianapolis77 »

That is the first time I encountered that issue, I hope you get good answers here.

brentp
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Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Just tap into one of the sensors and you should be good. I'd pick the one that increases in voltage.
Brent Picasso
CEO and Founder, Autosport Labs
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l8apex
Posts: 5
Joined: Sat Mar 07, 2020 4:05 pm

Post by l8apex »

I looked into this more and didn't like some of the things I found. The reason there are two sensors is for fault tolerance. The two sensor readings are active in the ECU, an algorithm calculates/compares the increasing voltage and decreasing voltage to find the position of the throttle, and if there's any variance it assumes something is wrong and throws codes and puts it into limp mode. Splicing into either of those sensors runs the risk, albeit minor, that there could be a voltage drop and the ECU wouldn't like it.

The accelerator pedal doesn't seem to have that. It only has two sensors for redundancy. So I tapped into the 2nd sensor, which is the fall-back, and it's working fine for me.

brentp
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Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

That sounds like a good plan. Glad you figured it out!
Brent Picasso
CEO and Founder, Autosport Labs
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