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Throttle Switch Voltage 700 86

posted by  someone claiming to be Rafael Riverol on  Tue Nov 6 14:11 CST 2001 [RELATED]

Recently, I checked whether the throttle switch signalled the ECU as soon as I started to open the throttle on the 1986 760 turbo. Indeed, it sent 5 volts. Pleae, someone tell me why 5 volts and not 12. Is this normal? Does voltage rise with throttle opening? Best regards.







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no such animal...switches only have resistance! 700 86

posted by  someone claiming to be JohnB on  Wed Nov 7 01:53 CST 2001 [RELATED]

The TPS only has open or closed resistance values. If you're reading voltage it comes from the ECU. A voltage reading means the switch is not grounding due to being open (a good thing off-idle) or a poor ground (a bad thing at idle).







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Re: Throttle Switch Voltage 700 86

posted by  someone claiming to be Tom M on  Tue Nov 6 14:51 CST 2001 [RELATED]

Probably because the logic circuitry in the ECU runs at 5 Volts. What you are measuring is an input pulled up to 5V.

The center pin (18) on the throttle position switch is connected to ground and when the throttle is at rest pin 2 and pin 18 are supposed to be connected together, therefore connecting pin 18 to ground.

When the throttle is off idle (above idle position) this pin (2) is pulled up to +5V. The signal is not analog, just one or zero.






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