K series Throttle Position Sensor readings

[Andrew Willcox]

Hi, I've just reset the TPS on my Caterham after if went out of calibration.

After resetting I notice on the OBD output that at full throttle it only reads 87% and 4% off throttle.  Car running OK but I was expecting the outputs to be 0% - 100%.

Is this normal?

[revilla]

Normal. Correctly calibrated on standard MEMS ECU it should read exactly 3.92% when closed. And yes somewhere around 90% when fully open. Only the bottom end is actually calibrated. The ECU only really uses the TPS for closed throttle detection (which needs the bottom end calibrating) and detecting the speed of throttle movements (which doesn't need either end calibrating). So all as it should be.

[Andrew Willcox]

Thank! Yes, closed reading is 3.92%

Not sure why it went out of calibration yesterday, was reading around 12% closed and car was not running well!  Second time this has happened in a few weeks, both times hot days when engine was really hot.  Have ordered a replacement position sensor to see if this overcomes - but at least I now know the cause of the problem and can recalibrate if necessary.

Andrew