Hey guys, Really like the forum, read a lot and this is my first thread. I bought a second hand 2005 prius (gen II) at 125k km. I am looking for some tips on what might be the problem with my prius. Soon after I got the car I got p0402 and p0505. After clearing the errors, I got back only p0420. About a month later, my car started randomly shaking both when accelerating and at idle. This happened 2 or 3 times in the span of 2 weeks. The CEL and traction control light started flashing. I stopped the car and started again like absolutely nothing happened 10 seconds ago. (This time I got only p0301.) Yesterday, the situation with the shaking was horrible and I got p0301. Naturally, average fuel usage went up a lot. Even at idle on the parking lot, I turn on the aircon so the engine would start - the feeling is like the car is going to collapse any second. I have recently used a new gas station, so I thought possibly bad fuel. However, if it was bad fuel, i should have gotten all misfire mistakes, right (p0300~p0304)? Please correct me if I am wrong. So if I am getting only p0301, the problem should be either the spark plug, injection coil, fuel injector etc. for cylinder 1. My car is currently at the mechanic's place, so all of the above are being checked as we speak. However, what I am worried about is that this shaking / lights flashing drama is happening at random. If it was any of the above, shouldn't is just happen all the time? When I went to the mechanic yesterday, I barely made it there. He was busy, I waited for 20 minutes, then he wanted me to drive the car for a bit to see the problem. This time the car was working like a brand new car. Absolutely nothing happened. He probably thought I was crazy. So yeah, he will closely inspect spark plugs, injection coils, fuel injectors etc. If all of them are fine, where should we look next? Any suggestions are more than welcome. Head gasket leak perhaps?
Thanks for the reply JC91006! I don't know about cars (this is my first one), but if it was a bad coil, shouldn't the symptoms of my problem happen all the time and not sometimes at random? And sorry if this sounds stupid, but what is SM-N900P?
Not necessarily, especially if it is to be a coil. As coils are on their way out of service, the repeated heating can intermittently cause episodic conditions as you are describing. A quick swap of the suspect coil to a non-suspect cylinder could be all that is needed to confirm the suspect coil is in deed the offending component.
"Random" symptoms with misfires is the norm in my experience. Thermal cycling and resistance change due to temperature can influence it.
Hey guys, Thanks for all the feedback. This is just a quick follow up. Got my car back. So far so good. Turned out is was the spark plug for cyl 1. The other ones were not great as well. Replaced 4 spark plugs, replaced MAF filter, changed oil as well. The mechanic said the coils looked fine and I didn't have to change them right away. The car is running very smooth right now. No codes no nothing. Hope it stays that way. Again, thanks for the quick feedback - this forum is great! Managed to learn a lot about my Prius! If anything else happens regarding this problem, I will update the thread.
You may also have gotten some water into the coil and plug area. If you haven't changed your plugs, it's also a good time to do it SM-N900P ?
Thanks for the feedback. Prior to changing the plugs and the filters today, I have experienced those occasional "slight hesitations" during acceleration as well. After taking it from the mechanic today, I did a 60km drive for fun, all seemed fine, no hesitations apart from the general millisecond hesitations from the HV battery/engine switch. Again, thanks for the all the comments and feedback!
Replying to an old thread in case it helps others. Had similar symptoms with errors being P301, P302, P304, and P0420 and the engine shaking on start up. I don't drive this car much anymore. 2005 Prius with ~248K miles. Drove it to the airport on a snowy day, left it for 5 days, came back to these errors. Drove maybe 2 minutes and stopped to check the oil, no mixing so no blown head gasket. Had to drove home ~29 miles and didn't care if it died. It got us home. Next day I called Boulder Hybrids, they're next to me. Paul is excellent and helped me diagnose the issue. I figured it's spark plugs, but he mentioned moisture on the coil pack itself. I opened it and sure enough, moisture. Spark plugs were last changed at ~172K miles, so it shouldn't be bad but it was and I think the amount of burnt oil could be the cause. Anyway, coils and spark plugs changed and it's back to normal. Don't know which of these 2 were the cause, likely spark plugs, but hope this is helpful to anyone who might encounter this in the future. I'm sharing the pictures of the spark plugs and coils in case it helps. The moisture on the coils were on the outside as far as I can see. Oil droplet looking. I didn't really see much inside, but it was a bit white near the opening. Note: I've had intermittent P0420 errors in the past 1 year. I think it's possible that a few undetected misfires could have happened causing this error to show up, but I don't know how the ECU detects misfires and if there are any possible misses.
A gen2 has a better engine than a gen3 especially from a head gasket standpoint. However many are oil burners. Coolant in the oil almost never happens due to head gasket failures in gen3s which fools many. Head gaskets rarely fail in gen2.
