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Check engine light on 2010 Prius, On steady. It's extremely…

Check engine light on...

Check engine light on 2010 Prius

Mechanic's Assistant: Does the light stay on, or does it blink?

On steady. It's extremely cold here, and the engine has been knocking badly when first started. Then it knocked at stoplights. Then the light came on.

Mechanic's Assistant: Are you fixing your Prius yourself? What have you tried so far?

Coolant is low, so I"m going to top that off. Oil is OK. Other fluid levels OK. Gas cap on tight.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

244,000 miles. No trouble so far. :) Thats' it.

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Answered in 20 minutes by:
1/5/2018
Ted Ritter
Ted Ritter, Toyota Master Tech
Category: Toyota
Satisfied Customers: 4,774
Experience: Toyota Master Tech, ASE Certified
Verified

Hello and thanks for visiting the site

Since the check engine light is on there are some diagnostic codes in the engine control module (ECM), the other lights such as vsc/trac will turn on by default, these are disabled while the computer detects a fault with an input from one of the sensors on the engine or transmission. The first thing would be to have the codes retrieved from the computer, most national auto parts chain stores can help you with that and they do this at no charge, if you could get that information to me in your next post I can help to diagnose whatever the problem may be or at least give you an idea of what should be done, looking forward to your reply.

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Customer reply replied 7 months ago
OK - I'll try to do that. I figured that would be necessary at some point, just wondering if there were some easy/obvious things to try first. Never had any sort of problem on my Prius before. There's one down the street.

Y​ou've already checked the gas cap, other than that not really anything else you can do yourself, if it's been running ok it may just be an emission control issue, the noise on cold starts is a little concerning but at that mileage, it's probably a little piston noise which would not be unusual.

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Customer reply replied 7 months ago
OK. Be back with that code (hopefully) in about 30 mins...

sounds good.

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Customer reply replied 7 months ago
P0302, P0300, P0304. Misfires.

There are a couple of common problems with this the ignition coils and/or the spark plugs, start with replacing the spark plugs, check them for any excessive oil deposits, replace them and clear the codes by disconnecting the negative battery cable for a minute or you can also clear them by removing the EFI fuse in the box under the hood, see if the misfires stop, if not you may have to replace the #3 and #4 ignition coils. Have you noticed if the engine is using excessive oil?

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Customer reply replied 7 months ago
No, I'm not due for another 1,000 miles and oil level is right on the button. Will do on the plugs. #3 and #4 ignition coils...the codes said #2 and #4 cylinders?

Yes, #2 and $ , my mistake, let me know how that goes/

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Customer reply replied 7 months ago
Ok. Local mech didn't want to work on it so I have scheduled a dealer appt. He did point out that it is burning coolant- white smoke visible and yes the coolant is indeed low again after a couple of days.
Oil is still spot on. Is there any possibility it is something other than a blown head gasket?

Thanks for the update

White smoke usually indicates an internal combustion leak, a small amount of smoke may be normal and due to the high mileage, the loss of coolant could be due to a leaking water pump, however this would not cause the exhaust emission.

This engine has a lot of miles on it so anything is possible.

The dealer should check:

the engine compression

Perform a chemical or exhaust analyzer test for excessive hydrocarbon content in the cooling system (internal combustion leak test)

A cooling system pressure test to locate any external leaks

If those tests pass then the misfire issue should be addressed

Please let me know what the dealer recommends if you have any concerns or question about their diagnosis..

Ted Ritter
Ted Ritter, Toyota Master Tech
Category: Toyota
Satisfied Customers: 4,774
Experience: Toyota Master Tech, ASE Certified
Verified
Ted Ritter and 87 other Toyota Specialists are ready to help you
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Customer reply replied 7 months ago
Wow. "Elrod" says it has a blown head gasket. Sounds like the only tests he did was to have his buddy go around to the back of the car and smell for burning coolant. But they had two rebuilds already priced for me when I came back to pick it up!I'm going to take it to a local family-owned shop that was my first choice (but they were booked) for a 2nd opinion. Your advice has been invaluable.
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