ECM problems!! Please advise!

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This pdf describes the situation they are attempting to resolve. Not completely uncommon in classic Prius, but not known to fail faster post-warranty. What the ECM does wrong is to complain if the gas engine starts too slowly. This is usually not described as 'sending false messages', but I see how it might be.

The need for a fuel tank assembly is not so common and apparently hard to diagnose. Were I you (and not interested in DIY install of an "054" ECM) from salvage), I would get the best offer from Toyota for just the ECM replacement. If the problem persists, fuel tank assembly later, and/or a new fuel pump relay.

Along the way, make sure somebody checks for soot on the throttle butterfly, because that thing could be getting sticky about now.

 

<div class='quotetop'>QUOTE(skyfield @ Aug 21 2007, 03:21 PM) [snapback]499901[/snapback]</div>

I'm about 6 hours from Memphis and the symptoms you are describing are exactly what I saw back in January. There is a subtle problem with a 'sticky' throttle plate in our model Prius that causes:

1) "no start" code - were you trying to start the car when it first happened???
2) error codes tell Toyota to replace the ECU and gas tank (and nothing about a sticky throttle plate)
3) it can be intermittent but seems to often occur during times of high humidity

If you can open up the hood and find the throttle assembly on the lower left below the air cleaner, there is a very strong spring that normally holds the throttle plate closed. See if you can grab the assembly with your left hand and open/close the the throttle. In my case, it was so sticky I couldn't move it.

I bought a $15 throttle and gas can cleaner kit from the Toyota Parts department and following the service technician's advice, sprayed like 'heck'. Since then, I've had no problem and now have the brushes to do the job right. You spray and use a narrow, long, nylon brush to scrub the area clean. Now I do it once a year, usually the fall oil change, and the problem is gone!

If you or your family members don't feel comfortable with this fix, send me a PM and I'll see if my wife and I can come over this next weekend (she likes to go to Tunica.) I'll take a short detour or we can meet somewhere and I'll be happy to show you' all how and do the job.

This really is a case of little problem that can be easily fixed for little money and you're on your way again.

Let me know,
Bob Wilson

ps. Doug is a little ways off right now but I'm in Huntsville AL.

 

If you can get Bob's help with this it would be great. I am in the Yunnan Province of China and not planning to cross the big pond for a while longer.

The part number of the newest revision of the engine control module ends in '54'. Earlier verions were a bit too quick to report an error. This ECM would probably be available from salvage dismantlers, and the installation is feasible for do it yourselfers.

The technical service bulletin has a complicated diagnostic procedure to decide what parts to replace. ECM is always (I think) and the fuel tank assembly and fuel pump relay are sometimes.

When I got tagged with this problem some years ago I was on a road trip. The closest Toyota shop said "replace all 3", but they had no parts stocked. I asked if I could just drive (1000 miles) home and the said sure. This at least is one case where if the car operates normally and the warning light does not immediately re-occur, driving on is OK. The home Toyota shop (a bit more skillful) redid the diagnosis and said replace just the ECM. They did, and no further related problems.

A dirty throttle butterfly can indeed interfere with engine startup. There is a TSB about that in Canada (at least) but not in the US. If cleaning that is all it takes, then great and you can shop for a 54 at your leisure. Or not.

The new model Prius is a substantial redesign. They have their own problems Let's not bother them.

DAS

 

PROCESS:
To clean the throttle plate, Toyota sells a kit that includes throttle cleaner, fuel injector cleaner
and vacuum hose cleaner that are safe for the catalytic converter, engine and fuel system:


The Toyota part number is 00054-00100 should cost $15-20:


If the throttle plate is sticking, you can test it by twisting the powerful return spring located just behind the oil dip-stick and under the air cleaner housing. If you can not move it, then throttle plate is sticking and cleaning it will cure the problem:


It is a strong spring but here I'm holding it with my finger. It rotates with the top going to the back and the bottom, where the stop tab I'm holding is located, rotating towards the front of the car:


Three clips hold the air cleaner cover. Replacing the air filter once a year is a cheap way to keep performance up and minimize dust and dirt:


Without the filter, it is easy to see the brass throttle plate. The air flow sensors are at the top and it is a good idea to avoid spraying it with cleaner. It is the throttle plate area that needs attention:


Just put the tube on the cleaner can and spray away:


If the throttle plate area is not sticking, it is easy to open with the hand. The first time, it was so sticky that I could not open it. So I sprayed the area and had a small pool of cleaner. I then started the engine and the powerful throttle motor opened it up. Thereafter, I turned off the engine and properly cleaned the area.


Once the throttle plate moves freely, use a combination of the long handled, narrow brush and spraying to clean the area:


My practice is to use at least half the can in the initial cleaning, drive around and use the rest. Be sure to dump the injector cleaner in the tank too. As for the vacuum hose cleaner, I understand a special tool is needed but I don't have one.

Questions?

Bob Wilson

 

Thankyou.
What is that clear braded looking hose to the front of the air filter?

 

<div class='quotetop'>QUOTE(patsparks @ Aug 25 2007, 09:03 PM) [snapback]502186[/snapback]</div>

That is an experiment on transaxle oil and negative differential pressure. We should really discuss it in another thread when I've got some usable data to share. I'm surprised you didn't ask about the AC power plug but that is a different experiment for which I only have limited data.

Bob Wilson

 

<div class='quotetop'>QUOTE(skyfield @ Aug 27 2007, 12:42 PM) [snapback]502779[/snapback]</div>

I suspect your local dealer has an equivalent throttle, injector and vacuum hose cleaning kit but I don't get the impression they are working with you. Autozone or other car part places should have similar cleaning kits. Look for 'catalytic converter safe' and you should be good to go.

The sticky problem was intermittent but I knew how to clear the code and had another experiment in progress at the time. Thinking I only had a warranty to 80,000 miles, I took out the other experiment to see if I could get a warranty swap of my ECU. Then the Toyota technician told me about cleaning the throttle and the problem went away.

The worst problems are intermittent ones because even after you clear the condition, if there wasn't a history of the problem, it is hard to tell if the fix worked. My thinking is carry the cleaning kit in the car, under the driver seat, and when the problem comes back, then test the throttle plate and cleaner.

The 'emergency brake light' sounds like a separate problem since the engine doesn't stall out when it comes on. I'd cycle the parking brake and/or try the 'backup adjustment' trick. In a parking lot away from things, backup briskly and hit the brake. This will 'adjust' the self adjusting brakes.

GOOD LUCK!
Bob Wilson