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04 forester issue, TPS?

hey everyone,

so I just recently purchased this car from a private party and while I knew I wasn’t getting anything special it is having far more issues than were apparent during the test drive.

A few days ago it died while idled at a stop sign and since then has had issues starting, and the AT oil temp light flashes. a buddy loaned me a code reader and it showed that the idle air control valve was having issues so I replaced that last night and it started up just fine, but the AT oil temp light was still present. I moved it down the block, and let it sit over night.

today, I went to take a look at it again and it would hardly start. now I’m getting P0122, P0123 stored codes and I had one for P1700 that was stored but it disappeared.

does anyone have any insight? I found a replacement TPS that is affordable, should I just go ahead and swap it out? anything I need to be aware of when doing the replacement, or is it just as easy as unplugging the old one and sticking the new one back in? It’s easily accessible so that’s not an issue.

thanks in advance.

A car with this many problems needs a slow and careful professional diagnostic analysis.


Replacing the tps may fix your P0122 and 0123 codes but the P1700 is telling you the transmission has issues. If the trans temp sensor is accurate, it could be slipping badly. That won’t get better. A good independent transmission shop might be your best bet.

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it never felt like a slipping transmisson. The light is flashing immediately after starting the car, so well before the transmission would be over heating, and while it’s just idling.

Maybe that means the sensor has failed and that threw threw the P1700 code.

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For this vehicle P1700 is Throttle Position Sensor circuit malfunction.


The one time I had TPS trouble I sprayed some electrical contact cleaner into it, rotated it through its range of motion a number of times, let it dry and reinstalled it. Problem solved.

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Have you tried to start it while depressing the accelerator pedal a bit?

In regard to the transmission I might suggest you check the final drive gear oil level. Many Subaru transmissions have been wiped out due to botched engine oil changes when the final drive was drained by mistake. Below is a pic of one. The final drive stick is on the passenger side and is the yellow handle just above the small red CV axle plug used to seal the transmission.

nothing changes when giving it a little gas. I checked all the fluids when inspecting the car and I kind of think the guy added some fresh transmission fluid right before I looked at it because it was a different color than it is now, only 1.5 weeks later. trying to be optimistic but I think I got lemon’d

A lemon is a new car with major defects.
You bought a 16 year old car, which may have been poorly-maintained and/or abused by its previous owner(s). Did you have it inspected by a mechanic prior to purchase?

my bad, I thought it just referred to being ripped off on a vehicle. no, I didn’t, and yes that was stupid of me. I checked all the fluids, test drove it, and everything seemed fine. 4 days later everything was falling apart. I’m not here to be ridiculed for vehicle purchasing practices just looking for advice on how to proceed.

Did you replace the throttle position sensor?

Asking a question equates to ridicule?
My best advice at this point is to take the vehicle to a independent mechanic’s shop that has a good reputation. Do NOT take it to Midas, Meineke, Monro, Sears, Pep Boys, AAMCO or a tire store unless you want less-qualified people working on your car.

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i went ahead and ordered one, it should be here Friday. I did read on another forum that it can trigger the AT oil temp light too.

Yes, the transmission control module relies on the TPS input for proper operation.


I will reiterate that transmission fluid and final drive lubricant (hypoid oil) are not one and the same. The final drive is separate from the automatic transmission part of that unit. Two fluids and 2 separate dipsticks.

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ahhh okay. I will take a look at that tomorrow. thanks for clarification. when I looked it up the internet told me final drive oil was for manual transmissions, and transmission fluid is for automatics.

installed the new TPS, and VICTORY!

Thanks everyone! I guess I got lucky and didn’t have to adjust it at all. The car is certainly running better than it did before.

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