Check Engine Light Stays On

If you want to get ahead of the jump you probably going to need to round up a scanner that's capable enough to do most of the things you want to do on your generation too read all the codes communicate with the full can bus system etc for that an AP200 is probably one of your best bets. The best $63 or so you'll spend on the car. If that doesn't float your boat and you don't ever think you'll need to bleed the brakes or do anything you'll pay for somebody to do all that then you could get a lesser scanner an Inova 31 series comes to mind 3120 3150. Again pretty cheap scanners you can buy them used on eBay and they will pretty much get all the codes you'll ever need from the Prius that you have misfire codes are very tricky just because somebody said they replaced the coils and did whatever you know they might have been used coils from other vehicles and so on people do this very commonly coils now are pretty inexpensive and pretty reliable I have some TRQ branded coils from Amazon on two cars about 60,000 mi in with no problem they are rated as they're heavy duty series of coil they are made by or for TRQ by some manufacture and by looking at them they look like they did a good job Time will tell they were $89 for the set of four there's no reason to be paying near $100 a piece that's outrageous. So it could well be you're having some coil problems maybe just get a new set like above and just replace them see if that cleans up the business or maybe it's been a long time since the plugs were done since you have the coils out it would be kind of silly if you personally haven't seen what's going on with the plugs I mean this is a pretty quick thing that can be done in 25 minutes changing the coils pulling the plugs noting the plugs look like crap and putting in the new ones you have dropping in the coils screwing them down and plugging in the plugs to the coils literally almost as fast as a talk it can be done none of these things are too awfully tight and shouldn't cause you any strife even at 74 years old and surviving a stroke I'm in like similar shape almost

 

what did the local guy do to your car?

 

Generally if you're running real Denso SK16 I think it is plugs what's supposed to be in the car they're 100,000 mi plugs under good conditions engine under good condition. So burning a little oil and 70,000 mi they should be starting to look like HELL. So probably a good idea to pull them see how blown out they look and maybe replace them I think you want to SK16-11s. And see what that does for you maybe even before you replace the coils If you order the coils and get a proper set of plugs not fakes I would change the plugs put the coils that you have back in run the car see if it cleans up If it does given the mileage you have and a match set of coils you have in a box now I would probably swap out my old coils for the new matched set and save the old set of coils just because and see how that serves you the newer coils will have better output so on and so forth If you get the TRQ they are supposedly higher density a little bit better materials whatever they seem to work well and you have your olds is back up in case something goes wrong.

 

Stay away from the Toyota Stealership for starters. They love to fix stuff that doesn't need fixing, so they can then be like we also now need to fix some other stuff as the bill keeps going higher and higher.

I'm south of you in Olympia if you ever need help... In high mileage Gen2 Prius those misfire codes most often happen when car is more than two quarts of oil low. There's other reasons, but that's the most common cause for those codes I see on Gen2.

Specifically, once you get up into the 200K mile range the engine will consume more oil. And even up to a quart of oil per thousand miles is fairly common. And I got way too many people who act like checking their oil is too hard to do and then text me they text me about how the red triangle is coming on when they go around corners, as in less than half the motor oil the engine needs and oil pressure light / red triangle is from oil pump sucking crankcase air instead of oil. I try in vain to get them to check oil level and add oil every third time they fill up the tank... But some of them refuse to do it. Drives me crazy!

For now just clear those misfire codes and let us know how quickly the codes come back now that the oil is at the correct level. Hopefully those codes don't come back and you get good at maintaining the oil level.

 

Tell me how low oil can cause a misfire in the engine. For the engine to run correctly without misfiring, you need the proper amount of air, fuel, spark from the spark plug, and compression. How does low oil affect any of those 4 things?

Sure, you need the proper amount of oil to lubricate the engine, but it has no connection to a misfire.

 

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Is it a courtesy only where I live ... or can any of you others just go to a good auto-parts store for a guy to put a scanner on your car FOR FREE and tell you the codes?!? Also by my house, any GOOD shop that I've done business with will do it FOR FREE if you come by when someone there has 5-10 minutes for you.

 

If 3 out of 4 cylinders was misfiring, you would definitely notice and feel it. For future reference, please get the actual code numbers. Someone telling you've misfires is their interpretation. If that dealership person was correct; P0300, P0302, P0303, and P0304 - would've been the error codes showing. Then the next question is, are those pending codes or live codes. I doubt those were live codes, because you would definitely feel 3 of 4 cylinder misfiring. Next step would be to look at fuel trim numbers to see how serious your issue is. If the engine is running smoothly, I'd dump a bottle of fuel injector cleaner in the tank and check fuel pressure & fuel pump. High mileage could equal clogged fuel filter and low fuel pressure, again OBD2 readouts should display and point you in the right direction - as long as the OBD2 jockey knows what they're doing.
If your local auto parts stores offers free scans, I would go get it re-read and see what pops up. Getting 37-38 mpg is kinda normal for wet, winter driving conditions in an 08 Prius IMHO.

Hope this helps....

 

so why did your local mechanic not reset the check engine light and you have to do it yourself? Funny that a shop has no idea what a check engine light is, probably "I only do oil change" kind of shop?

it's important to get the codes.. if you have the dense coils, just check the boot they could have some crack and a dab of dielectric grease will fix it or just buy new ones (they're very cheap) Lots of easy steps to check the misfires on the Prius and the coils and plugs are easy to swap (less messy than an oil change)

 

your engine will sound like it's knocking terribly and shaking.. even with 1 cylinder misfiring.

 

When crankshaft bearings get deprived of oil it can cause vibrations that sensors and ECU mistakes as a misfire. I've seen this problem several times with Prius that are more than 2 quarts low and experts here on PriusChat are the ones who explained it to me.... Sometimes it takes a little while after oil level is restored before vibration goes away and no doubt shortening lifespan of the engine. As far as I can tell this is specific to Gen2 Prius, not other generations...

 

Title of his post states: "light stays on" but OP didn't give us any details on that, but I hope he does in his reply...

 

The engine check light stays on my 'o5 Prius because one of the oxygen sensors has failed, probably oil contamination. This does affect the fuel economy and my '05 went from 4ltr/100km to 4.5 ltrs, then 5 ltrs/100km. I just put up with the light being on and the fuel economy, oxygen sensors are expensive and will only get oil contaminated again, so I just put up with the reduced economy, it would take another 200,000kms of the extra 1 ltr/100kms to pay for a new oxygen sensor, there are two of them, 400,000kms to break even ... yeah-nah

T1 Terry

 

Was the light on prior to oil change?

 

if your defective sensors are running rich especially the AF sensors then you'll be in a rude awakening someday because it's going to kill your catalytic converter.. and it's not cheap..