Computer Replacement Under TSB

Hi Linda,

Pls see attached TSB EG011-03. The no-start condition is pretty common on Classic Prius after a few years have elapsed. The typical DTC will be P3191, Engine Does Not Start.

I also had the engine ECU replaced on my 2001, suffering similar symptoms but in very hot ambient temps, around 120 degrees F during a Palm Springs summer trip.

The engine ECU replacement is covered under the Federal Emissions Warranty, 8 years or 80K miles.

 

Hi Linda,

Yes, most Classic owners with this problem will experience it during the winter. The reason for the problem is that as the engine ages, it takes longer to start especially if it has not been recently tuned or the throttle body is dirty.

Note that the original engine ECU has not "failed", i.e., there's no electrical component failure within. The point of installing a new engine ECU is that the firmware in the latter allows more time for the engine to start before the ECU logs DTC P3191.

For Classic owners who have this problem but whose warranty has expired, they should first try tuning up the engine using the correct iridium spark plugs (see owner's manual for plug specs), clean the throttle body, and make sure the engine oil viscosity is 5W-30 and not overfilled. Also ensure the engine air filter is in good condition.

Then if the problem continues, look for the correct engine ECU which may cost $300 from a salvage yard (the TSB shows the part number needed.) Alternatively, a new engine ECU purchased from the dealer will cost ~$1,000.

The engine ECU is located behind the glove box. It can be seen in the upper right after the glove box is lowered down (same procedure that you would use when replacing the cabin air filter).

 

Thanks for the input!

 

I have had this problem for a few years both in very cold and very hot conditions. Whenever I tried to bring the car to the dealer, the lights had gone off and they only said the codes referred to a "hybrid battery" problem but could not fully diagnose it without the actual lights being on. Since most of the time the car runs fine with no warning lights, I just keep driving. But now with below zero temperatures predicted, I am sure I will get warning lights, stalling engine (that then stays running after a few attempts restarting). I am wondering if this could be the ECU issue? My dealer, who I don't trust, never mentioned this possibility or any TSBs. Can I just bring in the car and ask them to check the ECU and be sure it is the newer one? I am still within the warranty. And thanks for all the great info I have gotten from everyone!

 

Next time you see the warning lights, I suggest that you immediately drive to your Toyota dealer (and if you have a choice of more than one, maybe you might try another one.) Then ask the service writer to have the tech retrieve the DTC, develop a diagnosis, and note all of this on the repair invoice for you. You might also keep a digital camera in the car, and when the warning lights come on, take sharp photos of the combination meter showing all lights, as well as the MFD warning icons.

If the DTC includes P3191, P3190 or P3101, then TSB EG011-03 is applicable (attached to my post #2 above). In that case, the tech should follow the instructions within the TSB. You may want to print and bring along a copy of the TSB to show the service writer.

If they want to replace the fuel tank (at your expense) then I suggest you first ask for evidence that the fuel line pressure has been measured per the TSB, and found to be below spec. Other posters have reported having to pay for a new fuel tank, seemingly as part of a program to throw parts at the problem.

 

Patrick, thanks so much for all your help. If I hadn't seen the info about the replacement of the ECU, I'm sure I just would have assumed that the warning lights were just from the cold and ignored them, since they always went off after the car warmed up. I brought my car in today to be checked, and sure enough, they replaced ithe ECU, still under warranty! Thank goodness for the internet. Hopefully no more exclamation points and check engine lights.

 

Beth David and Linda, along with ECU replacements as needed, please make sure that the throttle plate is not troubled by carbon deposits (Patrick did mention that). Also as your cars are 'of a certain age', it would be good to confirm the condition of the 12 v battery. Weak batteries have been known to cause hard-to-trace Prius irritations.

Here again we read of Toyota shops not being quite what they should be with regards Prius. This is a *real* irritation and there appears to be no cure for it (unlike the problems mentioned above)

 

I did replace the 12 volt battery a couple of months ago (from e learnaid, saving about $150 over the dealer's price) and the tecnician said that they cleaned the throttle as part of the repair today. Now I am learning about the transaxle fluid, which has never been changed! Is there a link to how to do this for a Classic Prius? I only see info for the newer ones. And thanks for your help, everyone!

 

Hi Beth,

I'm glad to hear that you got the ECM replaced without further difficulty. Regarding Classic transaxle fluid, the procedure is the same as with 2G with the following exceptions:

1. Use 5 qt of Toyota ATF T-IV
2. Tightening torque for the fill plug is 29 ft.-lb; for the drain plug is 36 ft.-lb (since the latter bolts into the steel pan.) It is deemed good repair practice to replace the two aluminum gaskets for the plugs.
3. A complete job requires removing and cleaning the transaxle pan and magnet. Therefore you will need a new pan gasket. Tightening torque for the pan bolts is ~6 ft.-lb, use a drop of blue Loctite on the pan bolt threads.
4. I suggest replacing the transaxle fluid (and cleaning the pan) at 30K mile intervals.

You will be very impressed by the amount of grey muck that has accumulated on the pan and magnet. Should you find plastic bits and other weird material, that may be early warning of a pending transaxle failure (due to stator wire insulation starting to chip off.)

 

I checked the ECU on my 01 and it's a 47030. I bought this car used. I got the service records from a Toyota Dealership and the ECU was recommended to be replaced at 83,813 miles in May of 2007. The original owner had all of his/her work done at the Toyota dealership. It seems funny that the dealer recommended the ECU change after the California Emissions warranty had passed. Should I press the dealer on this TSB or will I be fighting a loosing battle?

 

Hi popimp,

If the car had 83K miles in 2007, what does it have now: >=100K miles?

I think you would be wasting your time to try to get an engine ECU at no charge. If you look for a salvage ECU (on eBay Motors for example) you should be able to buy the correct one for ~$300 or so and if you can install it yourself then you will be done.

 

Patrick thanks for the info. I'm not really sure I need the ECU, because the car starts and runs fine. Would having the new ECU do anything to make the car better? I'm trying to figure out if the $300 is worth it or not? The car has 105K

 

Hi popimp,

I attached the TSB to post #2 above. Following is the introductory sentence: "Some 2001 through 2003 model year Prius vehicles may exhibit a Master, Hybrid, and M.I.L. warning light “ON†condition if an abnormally low engine power output or failure to start has been detected during a particular THS drive cycle."

If you don't have an engine no-start problem then you don't need the current revision engine ECU to be installed.

 

Hi Patrick,
Today when I went to start my car (after not driving it for a few days--and it was also very hot out). I again got the exclamation point and "take to dealer immediately" icon. This is after the ECU replacement this winter. As I mentioned before, this seemed to happen in very hot or very cold conditions. Now, after the car has cooled for a couple of hours, it starts fine, no lights, all is well. The only Toyota shop in town is now owned by crooks, and I hesitate to take it there for a diagnosis. Any suggestions? Is there a way to tell if the main battery is failing? The car has 65000 miles, it is a 2002. Thanks!

 

Hi Beth,

Please describe the exact appearance and location (dashboard or MFD?) of the icon that you mentioned above.

Three possible warning icons will appear on the Classic MFD. They include the hybrid vehicle warning icon (an outline of a car with an exclamation point), the traction battery warning icon (a picture of a battery) and the power steering system warning icon (PS).

If the traction battery is failing, you should notice driveability issues. For example the gasoline engine might run whenever you depress the accelerator pedal. MPG and acceleration will be much worse than normal. You should see one of two icons appear in the MFD: either the battery icon or the hybrid vehicle icon.

What is the age of the 12V auxiliary battery in your car? If it hasn't been replaced yet, maybe it might help to replace that battery now.

Can you find another Toyota dealership in a different town that you might be able to take your car to?

 

The triangle with exclamation point lights up near the "ready" area, and on the MFD it is the outline of the car with the exclamation point. I replaced the 12 volt for the first time last November, and since then have been using a battery minder on it because often days go by without driving. As I said, could the hot temperatures have anything to do with this? It is fine now that it is cooler out, and last summer I had the same issue. (But I have had the ECU replaced this winter, assuming there would be no more warning lights. Wrong!)
I actually had just checked the voltage of the 12 volt with the display screen right before I started the car. Was 12.5. The next closest dealer is 40 miles from here. And the car is driving fine--shuts off when it should, the inverter pump is churning, no apparent problems.
I also changed the transaxle fluid in January and it looked pretty good--fairly clear and not much gunk.
Thanks to you and this forum I am learning so much!

 

Hi Beth,

Please find your repair invoice and confirm the part number of the replaced ECU. The Prius has many ECUs and I want to ensure we are both talking about the engine ECU being replaced, aka ECM, part number 89661-47054.

Yes, hot temperatures can cause engine no-start problems. If fuel line pressure is too low, maybe vapor lock is preventing the reliable flow of fuel. The minimum fuel line pressure is 294 KPa or 43 psi at idle speed. You can ask for the fuel line pressure to be measured. If it is too low, then the fuel tank will have to be replaced (since the fuel pump is located within.) Or, a marginal circuit opening relay might have resistance across the switched contacts, thus lowering the voltage provided to the fuel pump. The relay can be tested by applying 12VDC across the coil terminals and measuring the resistance across the switched terminals using a digital multimeter. The resistance should be 0.5 ohm or less.

Another possibility is a very dirty throttle body and throttle plate. Classic is more prone to suffering driveability symptoms from this than 2G.

Your post back in January indicated that the throttle body had been cleaned. However if you want to verify this, you can remove the engine air filter housing cover, then remove the engine air filter and take a look at the throttle body interior and throttle plate that is exposed. Rotate the throttle plate with the car IG-OFF by turning the spring loaded shaft with your hand. Use a flashlight if necessary to get a good view.

If you see lots of black muck coating the metal parts then they should be cleaned using throttle body cleaner. The minimum amount of cleaner should be used since it is going to drain into the intake manifold, then will be burnt by the engine.

If the engine air filter is dirty (hold up to sunlight and see if light passes through the filter or not) then this would be a good time to replace it.

Do your local discount auto parts stores read diagnostic trouble codes at no charge? If so you might ask for this to be done and see if any codes can be retrieved, then post. Note that a generic code reader may or may not retrieve the codes logged by the various ECUs in your car. Only a Toyota diagnostic device or laptop computer is guaranteed to retrieve all codes.

 

Patrick,
Wow! You are so helpful! So.. the throttle body looks clean, I just changed the engine air filter and I am on my way to the Autozone to see if they can read the codes. It was the correct ECU as well. I am not quite sure what you mean by "applying 12VDC across the coil terminals and measuring the resistance across the switched terminals using a digital multimeter. The resistance should be 0.5 ohm or less." You mean on the 12 volt? Switched terminals? Could you explain how to do this? And by the way, engine starts just fine today--no lights of any kind! Hmmm... Thank you much.