The codes 42, 43, and 71 are what apeared on the diagnostics. I need help bad. My truck is a 94 toyota sr5 4x4. it reads the oil pressure relly low about five min after im driving.

 

Besides the codes, what all is the vehicle doing? How is it behaving? Did these codes come all at once?

 

http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

See page 177, it refers to page 193 for code 43 and 251 for code 71, that's if you have a V6.

If you have a 4 cyl see here:
http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf

Here's the whole FSM for those other pages:
http://personal.utulsa.edu/~nathan-b...fsm/index.html

 

well my truck has a v6. it behaves kinda weird though. The reason i say this is because not only does it get really bad gas mileage(like im runnin a V8), but it feels like its not giving me all the power it should have. It almost feels like im running a four cylinder, but with the gas economy of an eight. and like i mentioned earlier, it marks the oil pressure really low after about five minutes of driving, even though the dip stick for the oil marks it at full. your probably thinking that it may need a tune up for the gas mileage , but i just did an entire tune up on it, including the gas filter, but it ran the same.

 

Have you used a mechanical oil pressure gauge to verify the oil pressure?
Also, what weight is the oil you're using?

 

The dipstick can read low and you could still have normal oil pressure at the same time. So, that's not a real indicator. Oil pressure being low could be caused by larger than spec oil clearances or a fail oil pump relief valve. Run a google search on oil pressure and how it is created. Also, what is low to you? Where does the gauge sit? It's normal for oil pressure to be higher at start up....particularly when the motor is cold....and then lower as it warms up. Also, oil pressure increases.....or is supposed to, anyway....upon acceleration and lower when you release the throttle. Given that, what abecedarian suggests is the way to check it. But, you might also inspect the sending unit and the connector. See if that's loose or something.

Again, though.....did the CEL codes come all at once? It's odd for circuits like those that are unrelated to happen at the same time. I'd suspect an ECU issue, but hate to jump to conclusions about that. Do a visual inspection of the ECU and the connectors. Is there anyway for water to have gotten inside the cab?

 

When i had the check engine light checked, all three codes appeared all in the same diagnostic check, i even bought the owners manual just to see what they all ment, but i still dont have a clear enough idea of how to solve them because of the fact that this is my first time dealing with a toyota vehicle. When i say that the oil is marking low, i mean it marks it at the first mark on the oil pressure indicator, and it stays there whether i am accelerating or have the truck just idling. When the engine is cold though, i drive it and it does mark it all the way to the middle of the indicator when i accelerate, but thats only for about five min. About the oil pressure tester, i havent tried that yet, i have no idea how to check it. What do you guys think about the oil pressure relief valve having something to do with it. Oh and about the oil i use, its 10-30 Mobile 1 full synthetic oil.

 

The relief valve is a possibility. But, that (the oil pump) really is a biotch to pull and replace before you've actually checked the oil pressure. After all, the sending unit could just be bad.....and is much easier to replace. Cheaper, too.

As for the codes, I would check all your electrical grounds. That's the only thing I can think of that would cause such a problem.....aside from the ECU itself.

Come to think of it, a bad ground could also cause an intermittent sending unit/pressure gauge.