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TPS signal dropping to zero?


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I've noticed something slightly weird going on with my Nissan R33 GTR, and want to rule out the Vipec Plugin (or find some help!). Whilst accelerating, the TPS signal sometimes drops suddenly from say 50% to zero (triggering the over-run), then immediately picks up again back to ~50% all in the space of 2 seconds, and while the pedal position stays the same. I have fitted and calibrated a brand new TPS sensor but the behaviour persists. One thing to note is that I changed the default J1 jumper position soon after first installation due to an issue with the 4WD light (turns out this might have been an earthing issue with the G-sensor), and never changed it back. Has anyone seen this before?

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Hi James,

Does the switch only ever read 0 and 50 %.

After you carry out a TPS calibration does it read from 0 - 100% at all or always 0 - 50 %.

Either your not doing the TPS calibration correctly or the TPS connector is fitted to the idle switch side of the TPS SWITCH itself.

The Skyline TPS has 2 connectors on it, on is a variable potentiometer and the other is an Idle input switch used for Auto trans kick-down etc.

Can you hit the F12 key go to Analogue Volt Input page and check the TP MAIN VOLTAGE from closed throttle to open throttle.

You should see under 1 volt at closed and something between 4.2 - 5.00 volts at WOT.

I have installed a lot of PNP's to Skylines and never seen this issue.

Also if you read the issues page in the Skyline PNP Manual it mentions sometimes striking issues with Auto trans TPS input requiring 12 volts instead of 5 volts.

Let us know what you find.



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Hi Dave,

I don't think I described the behaviour particularly well in my first post (the car is a 5 speed manual by the way). The TP (Main) log shows the throttle behaving itself for 99% of the time, going from zero at idle to WOT (very occasionally officer), and when it does misbehave it is not always from 50% throttle. This morning the strange 'throttle drop' initially occurred at 21.9%, where it dropped to 0.6% and back up to 20% in less than 1.3 seconds, and repeated a further three times in quick succession. Corresponding short-period changes are shown in the MAP and AFR graphs, so 'something' is definitely happening. I initially thought this must be some sort of 'cut' activating, but it is looking more likely that what I'm seeing is in fact an effect of something else. I will quadruple check the TPS voltage tonight, and give the throttle cable itself a look over.



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