You might want to try pulling the instrument cluster and reseating the connectors. The speed sensor is processed through the cluster.

 

Where to start... Pd stands for pending though odd since it tossed the full code.
P0171 usually points to a o2 sensor which this model is common to need. Check what records you got with the car if they were replaced make sure it was a denso as ive read so many posts from bosch sensors that bring the power loss and other odd issues. Odds are you need a new denso sensor but if you can get a live data obd2 reader you can confirm that by watching the voltage swings.

As for the gas millage a new o2 will help but check for intake leaks or worse still fuel line leaks. You can check for intake leaks with carb cleaner but fuel lines require a hoist. Also a pricey job to get the lines so would be a good reason to sell the car.

I agree with the previous post to ensure everything is connected nice and tight if you need a new cluster pm me i have 3 lying around im not going to use. Still check the ground wire located above the clutch pedal where the relays go. Another very common issue.

Let us know how it goes and welcome to toyotanation.

 

If it has a plastic intake manifold then replace the intake manifold gaskets.

 

Thank you for the help! these are all things that i had not thought of. In fact now that you mention it, the instrument cluster, it is in the dashboard. When it sits in the sun the sun beats on the dashboard. Like i had mentioned earlier, i swear when the car sits in the sun it starts actin' up. As an amateur mechanic with ten yrs experience, even I know that what i said about the car in the sun sounds ridiculous but i swear it happens. Every single time i leave it in the sun. I can count on it. I started to park it under my neighbors carport (with their permission of course lol) so that i can at least get to a destination without having to gas up. So when the outside temp is high, it starts acting foolish. Could there be any correlation? my mechanic buddy says im the fool but i know im seeing something here. oh and heres the crux, i find it odd that both the p0500 VSS and the p0171 o2 sensor code go at the same time. I do know that both those components are in the same relative location in the engine bay by the back of the motor.

Anyway, im wondering if maybe the instrument cluster has a short that becomes pronounced when it heats up inside the car. Maybe the heat is causing it to shut down sorta like when a laptop or a computer gets too hot. i probably dont know what im talking bout but im a dreamer for sure lol. I may give you guys a shout out about that instrument cluster and just replace it if im gonna do some dash work.

oh and on a side note, i replaced the ECM/PCU (computer) and it still does this so im pretty certain its not the computer.

 

Your MAF has an intake temp sensor in it as well.
If that is miss calcing the temp when it gets warm outside that can cause some major issues too.

 

Another note about reseating the connectors on the cluster. The connections for the speedometer are the five screws that also mount it to the cluster. Loosen and retighten them, use contact cleaner if necessary. The connections to the speed sensor are the screws labeled SI and SE.

When I swapped my instrument cluster to add the tach, I swapped the speedometer to keep my actual mileage. When I put it back together and took a test drive, I lost the speedometer, noticed poor performance, and set the CEL. I reseated the connections in the cluster, put it back together, and haven't had a problem in more than a year.

 

Tried too clean it up for you. Hope this helps.


Vehicle: 1998 Corolla LE
Mileage: 200K
Transmission: Auto


Complaint: 1 week into ownership car starts using excessive fuel and the vehicle speed sensor wont work. Erratic transmission shifting and speedometer and odometer are INOP

Additional Comments:

Generic code reader(?) codes are p0500 code, p0171, p0171pd.

Problem is Intermittent over a few weeks.

Changed VSS and MAF in an attempt to resolve problem, cleared fault codes.

Problem happens more when the vehicle is parked in the sun and it is warm. Temp gauge reads 95 degrees. Doesn't happen or is less frequent if the car is parked in a cooler area, i.e. shaded area.



Also its helpful to note things like aftermarket work that has been done previously, i.e. aftermarket sound system, alarm systems, etc. Whether still on the car or not.

 

On most cars with MAF's to test them I disconnect them and let the car run off the o2 sensor. I have a 98 corolla though and I don't recall having a Mass Air Flow sensor. And does VSS mean vehicle speed sensor?


When the car is reading 95 degrees what is the ambient temperature outside?

 

240 miles to a tank is bad? I thought I was doing great at that mpg in my 01 CE... but that's also considering I was driving a Blazer before and was lucky to get 11-12 mpg

 

Yeah that is TERRIBLE for this car!!
This car can get anywhere between 30-35 MPG when in tip top shape!!

 

these cars have a low fuel light?

 

Mine does?

 

Has a low level light for the washer fluid too. I rarely see the gas light but it has come on a time or two