Red triangle/Check Engine lights came on on the freeway!

This is a typo. The service writer probably meant to write, "replaced inverter pump and refilled new coolant"

In preparation for your upcoming road trip, I suggest that the throttle body interior and throttle plate should be cleaned. That is a documented cause of engine no-start problems with Classic Prius. If you haven't replaced the iridium spark plugs yet, it would also be good to do that now, using the correct Denso or NGK plugs (listed in the owner's manual.) Do not allow the installation of other spark plugs. Also check the engine air filter and replace if it is dirty.

As a preventive maintenance measure, I also suggest that you replace the 12V battery soon.

Then, if the engine no-start problem repeats, I suggest that you ask for the engine and hybrid vehicle ECUs to be reflashed with the latest firmware. You may recall SSC 50P which was a recall associated with 2G Prius stalling issues, back in October 2005. The SSC reflashed firmware for those two ECUs.

 

Any decent mechanic can do the throttle body/throttle plate cleaning and the spark plug replacement. It will take 15 min. for the cleaning and less than one hour for the spark plug replacement.

Regarding the throttle body cleaning, normal practice is to flood the interior with throttle body cleaner. However the Toyota recommended procedure is to remove the air cleaner housing for access to the throttle body. Then apply cleaner to a clean cloth or paper towel, and use the cloth/towel to scrub out the interior and throttle plate. The point of this is to minimize the use of cleaner, which may carry dirt down the throttle shaft into the throttle body motor.

The spark plugs should either be purchased at your local Toyota dealer's parts counter or online. They will cost ~$12 each at retail pricing. It is possible that a local import auto parts store may carry the correct plugs, call ahead if you are considering that alternative.

The 12V battery is a non-standard size and MSRP is $138.70. However southern CA Toyota dealers may charge more, call around to determine local pricing.

 

I agree with Patrick, it is an excellent idea to make sure that there aren't any problems with air and spark delivery. Any competent independent mechanic can do this, and an independent Toyota specialty shop would be even better. I would suggest that you not go back to the dealer that read your codes, given how you were treated.

In addition to the throttle body, I would also suggest that you have the MAF (mass air flow) sensor cleaned, and PCV valve replaced. Also, if you have never had the transaxle fluid changed, do it as soon as possible.

On the 12V, a little outfit in Sylmar sells the vastly superior Optima 12V battery replacement kit, if you find the SoCal dealers charging excessively for the dumb motorcycle oem 12V Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 - 10

Changing spark plugs, PCV, and cleaning throttle body + MAF should be less than $200 for parts and labor.

Transaxle fluid change runs around $100-$125.

 

And just so you know, the transaxle fluid must be Toyota ATF WS. The only other alternative is Redline D6, which is usually more expensive. Remind your mechanic that there is no torque converter, it is a simple drain and fill much like what would be done for a manual transmission.

 

The seam at the center of the plastic cover for the cowl tray can leak and allow water to drip onto the engine block and find its way down the spark plug wells. Ask them to apply a bead of sealant at the seam. Glad to know you may have found the root cause of the problem. Good luck!

 

Given your msg below, I am surprised to find that your engine ECU did not log DTC P030x, where x can be 1 to 4, and corresponds to the cylinder number of the spark plugs that have a rusted shell.

As 2009Prius indicated, a known problem is water dripping down the cowl at the center seam, landing on the engine valve cover, and entering the spark plug tubes. Eventually this will cause an engine misfire which should be reported by DTC P030x as stated above.

This might be the root cause of your engine problem, but I still encourage you to get the throttle body interior and throttle plate cleaned out, using the minimum possible amount of throttle body cleaner as earlier detailed.

 

Good. Now that you have had this service done and obtained that AAA coverage, if you bring along an emergency supply of food/drink and have a fully-charged cellphone then you should be fully prepared for your road trip.

I'm wondering why your Toyota dealer's service dept did not suggest that the spark plugs should be checked, esp at your car's odometer reading. This shows that the tech is too reliant on the DTC codes, which is a bad thing.

 

Hey, that might just have been the problem. Good luck on your trip!

 

I think filing a safety complaint at Home | Safercar -- National Highway Traffic Safety Administration (NHTSA) is in order. Unfortunately, it looks like we only have possible root causes of the problem.

Hopefully, somebody added sealant as 2009Prius suggested (if that's the correct fix for that issue/your issue).

(I'm no repair expert... you've already got some of them here on this thread.)