YnotDIY Posted December 12, 2018 Share Posted December 12, 2018 Hey Ya'll, After a lot of hours trouble shooting some issues with my 88 GL (SPFI 4x4) I found a faulty TPS. I've now installed and calibrated 3 new (used) TPS's and I can get NONE of them to read within' the FSM specs. FSM says this.... back probe terminal D with one probe and ignition ON, but CAR NOT RUNNING (actually found this to be incorrect, need to probe terminal C to get a reading) and connect other to a good ground. With TPS already calibrated reading with throttle fully closed should be about .5V. At throttle fully open reading should be around 5V. So I should have a reading from .5V - 5V that goes up gradually as I open the throttle and goes back down gradually as it is closed. Here is my issue. NONE of these TPS's will read up to 5V at full open. I'm getting around 4.2V max. HERE IS MY QUESTION What are others getting for voltage readings on their TPS's? Anyone get a reading at 5V? Please post some answers below. Cheers! Quote Link to comment Share on other sites More sharing options...
idosubaru Posted December 12, 2018 Share Posted December 12, 2018 (edited) I remember XT6 TPSs would not calibrate to the FSM specs either and I posted about it like 20 years ago on the old yahoo forums I think. I think the FSM May be wrong or incomplete in some way. Its been a long time since I did one but from ancient memory - turn until the sensor “engages” (use whichever metric seems appropriate) right as the throttle body is opening. Want The throttle sensor to start registering once the plate starts to open. The throttle cable and cam will move some before the throttle plate in the throttle body starts to move. So pull the intake so you can see what the plate is doing. Get it close then tweak from there. Just do it manually like that, it’s not a big deal. It’s not really the precise science the FSM makes it sound like. I thought it was super critical years ago and it’s not I mean it is but it’s simple, not complicated. Someone blindfolded could literally do it without much issue. Keep turning until it works then tweak to dial it in youre positive it’s properly engaged with the throttle body? Also - are you checking at the sensor or further down the harness? I had one years ago flaking out, swapped TPS and got the same results - and it ended up being the harness right before the TPS (where it starts to bend) had a short in it. I cut a used one from another car and swapped it out and all was good. Edited December 12, 2018 by idosubaru Quote Link to comment Share on other sites More sharing options...
naru2 Posted December 13, 2018 Share Posted December 13, 2018 I think you have found the reason the later 1989 FSM does not mention TPS voltages at all.Just resistance measurements. Check it out here http://jdfinley.com/file-downloads/subaru-manuals/ Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 13, 2018 Share Posted December 13, 2018 It's fairly normal to not go all the way to 5v on TPS sensors. 4.5v is typical. Also you can't get 5v if the 5v supply isn't putting out 5v. Check the supply voltage from the ECU. GD 3 Quote Link to comment Share on other sites More sharing options...
Steptoe Posted December 16, 2018 Share Posted December 16, 2018 I had an spfi, an mpfi spider and a non spider mpfi to play with and could only ever achieve 0.4 to 0.5 V change through entire closed to full throttle positions. I needed the modern accepted ranges of 0.5 to 4.5 V for my application and ended up getting a new adaptable unit to fit up I think my sub units worked in reverse or I was working wires in reverse Quote Link to comment Share on other sites More sharing options...
YnotDIY Posted December 18, 2018 Author Share Posted December 18, 2018 On 12/13/2018 at 1:02 AM, GeneralDisorder said: It's fairly normal to not go all the way to 5v on TPS sensors. 4.5v is typical. Also you can't get 5v if the 5v supply isn't putting out 5v. Check the supply voltage from the ECU. GD @GeneralDisorder I checked the supply from the ECU and it's putting out 5v. The TPS seems to read around 4.2-4.3v at full open. It's running great though so I'm not that worried, just wondering if anyone else is getting the same under 5v readings as me. Unless anyone it getting a higher voltage reading at full open then I'm gonna say 4.2v is a pretty normal read. Quote Link to comment Share on other sites More sharing options...
YnotDIY Posted December 18, 2018 Author Share Posted December 18, 2018 On 12/12/2018 at 7:28 PM, naru2 said: I think you have found the reason the later 1989 FSM does not mention TPS voltages at all.Just resistance measurements. Check it out here http://jdfinley.com/file-downloads/subaru-manuals/ @naru2 thanks! It's good to know they switched it up like this. I'll have to test again and see if it checks out according to these specs. Incase anyone is curious if you follow the link. TPS is listed in EA82 Part 2, Section 2-7, pgs. 14-15 Quote Link to comment Share on other sites More sharing options...
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