intrmsof2

So I've had a scanner on my ES ('97 model) a couple times recently and I've noticed that at full throttle, the reading is 74.9% open. I want to check the TP sensor, but I can't find what the resistance values should be. If anyone has that information I would appreciate any help.

Also, I have the specified voltage values, but that test requires the harness be connected. Anyone who has worked with these harnesses though, knows that back-probing them is difficult if not impossible. Does anyone have a suggestion as to how I should go about probing that harness?

I know I'm asking some pretty technical stuff, but I'm kind of stuck on this one, so I would appreciate any help at all.

Pheonix

Page 38 of the diagnostics.pdf.


That's normal, provided that when u hit that 74.9% it says you enter closed loop.



You can backprobe, but you risk cracking old plastic (and the old rubber gasket seals in all the harnesses break & pull off just via time). If you're actually gunna check the voltage by hand, you need to just splice into the VTA wire.

MoreMGD32

iTrader: (1)

What exactly is a scanner?

Pheonix

a scanner scans the ECU for codes.
a logger logs snapshot information from the ECU.

MoreMGD32

iTrader: (1)

so what is running at 74.9? voltage?

why wouldnt it run completely at 100% whats is causing the resistance?

Pheonix

No, the ECU is reporting that the TPS sensor is 74.9% open when he's at wide open throttle. Which is acceptible.

intrmsof2

I was actually able to backprobe around the plugs in the back of the connector and test the voltage and it's right in range. I'm still not sure exactly why toyota chooses to put wide open throttle at a value of 75% though, as I verified that reading with another scanner. Interesting stuff. Thanks for the help.

On a side note, the "scanner" i'm refering to is a diagnostic scanner, which is a computer that communicates the the OBD-II setup on your car, reading trouble codes, displaying engine data, and allowing assorted other access to the computerized areas of your car.

Pheonix

It in the manual as to why, along with the training manual.
The reason is because of manufacturing, and mounting tolerances over time. Nothing gaurentees that TPS sensor isn't going to spin around in it's mounting & throw it's calibratin off after years of use.


Because of that, Toyota only reads the throttle angle for 2 major upfront puroses:
1) When it get's to around 75% WOT, it swaps from clsoed, to open loop (Every OEM does this)
2) It reads the quick responce on the pedal. Fast accellerations give ECU enrichment. In the opposite. On the latest cars, fast depression of the pedal activates the brake lights before you can even hit the pedal. (That does not apply to you).


Every OEM does the same thing. (Doesn't use the top end of the sensor range) it's just isntead of calling everything over XXX voltage output 100%, its telling you that even tho the TPS sensor is maxed out, XXX voltage is only XX% of the voltage scale the sensor can provide. Anything past about 75% on all Toyota systems is open-loop. There-hence-forth there is nothing gained by that sensor providing even more output.



Make more since now?