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Guest Message by DevFuse

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TPS Sensor in 1994 Subaru Impreza 1.8L

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6 replies to this topic

#1 NotImprezive



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Posted 22 August 2013 - 10:00 PM

Ok, Subaru people, help me out here!


I just bought a 1994 Impreza 1.8L in great shape for my teenage driver. Just one little problem....


When I test drove it I noticed that a light on the dash blinked "POWER" for a few seconds after ignition, then disappeared. When I asked about it the seller was clueless. The test drive was okay. It's a bit underpowered but it seemed to shift and run fine and it was super clean for a '94. Usually that means someone has taken really good care of it, so we made an offer. A couple hours later we went for a longer drive and noticed sometimes it would shift funny. Like it was downshifting and upshifting under throttle in a random way.


 Started looking closely  at the owners manual and online. Turns out the "POWER" light blinks sixteen times after ignition when something goes wrong with some part of the transmission system? Found some more info and tried a few things. I pulled the fuse (#14) for ten and put it back in. The light blinked like before. I successfully accomplished the "Subaru secret handshake" voodoo and it gave me code 31- throttle position sensor. I have not disconnected the negative battery cable for a reset.


So I Googled that a bit and I've found it's easy to replace. Like $200 new and $50 from a junkyard. A couple of screws and voila. I just have a couple questions before I do this......


1) If the TPS code is the only code flashing, does that mean the TPS is all that's wrong with it?

2) Should I try the battery cable thing first?



Thank you in advance!!




#2 xbeerd



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Posted 22 August 2013 - 11:23 PM

could be faulty wiring possibly too.  


if its like mine, you could clear it via the battery, and it'll run fine, but it'll come back maybe couple start cycles down the road, maybe couple days, but it'll probably come back, Luckily that car got Tboned and i never had to finish solving that problem, LOL

#3 NotImprezive



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Posted 23 August 2013 - 12:04 AM

Thanks for the answer!


One question. When you cleared it via the battery, did the weird shifting issue go away as well as the blinking?


Good point about the wiring. Is that a weak point on Subarus?

#4 heartless


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Posted 24 August 2013 - 10:24 AM

nearly 20 year old wiring is a weak point on ANY car - not just a Subaru.


a lot of heat is generated (and held) under the hood, and heat will eventually cause wiring (and other things) to become brittle and easily damaged.


inspect the wiring for signs of chaffing, nicks, cuts, localized discolorations (getting hot/burning), swelling (corrosion), or anything else that doesnt look "normal".

Same goes for the connector - make sure there isnt corrosion inside, that all the pins look clean and all are about the same color. good, moisture proof connections will usually be shiny brass still, but they could be a dull, even color and still be fine - you are looking for hot spots (burned looking) and/or corrosion.

#5 johnceggleston


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Posted 24 August 2013 - 10:38 AM

the TPS will / can throw a trans code and / or an engine code.


the newr cars would differentiate between a TPS circuit problem vs. a TPS malfunction.

i don't know about the 90 - 94 cars , not my generation.


by ''handshake'' i assume you were reading the trans codes.

wiring is a pretty good bet.

but maybe the trans wiring, not the TPS wiring, maybe.

the TPS is working for the engine and ECU,

but some how the TCU and trans do not think so.


if you do replace it make sure you adjust it correctly.


another thing that will make the trans act wonky is bad / dirty / corroded grounding points / wires.

Edited by johnceggleston, 24 August 2013 - 10:39 AM.

#6 ivans imports

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Posted 24 August 2013 - 10:42 AM

have a complete intake from 94 ej1.8

#7 Fairtax4me



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Posted 25 August 2013 - 10:52 PM

Check the TPS with a multimeter. Center pin to either of the other pins will show either steadily increasing or steadily decreasing resistance. If the reading is jumpy (easiest to see with an analog meter since you can watch the needle) the TPS is bad.
TPS adjustment is also critical. Check the throttle bore for carbon sludge buildup. It can keep the throttle plate from closing all the way and will throw the closed throttle voltage signal out of spec.
Also possible the previous owner tried playing with the throttle stop screw and pushed the TPS out of range. Both of these would likely also cause the CEL to be on.
Check that the CEL comes on for a few seconds during the bulb check after starting. If it does not come on the bulb may be burned out. You should also check the ECU for stored codes.

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