2007 Prius stalled and won't start - Dealer is going to replace the computer

Is your 12v battery the original? It's possible that it is going bad.

 

It's hard for us to comment without knowing what DTC (diagnostic trouble code) was logged by your car. I suggest you ask for this.

The DTC code has the following format: A#### where A is an alphabet character, typically P, C, or B. # is a hexadecimal character, 0 - 9 and A - F.

In general, it is very unusual to come across a situation where an ECU has to be replaced unless some abuse happened such as accident damage or incorrect jump procedure.

 

You are in CA, make sure you are still not covered by the extended emissions warranty. I don't have my book handy, but I believe the ecu may be still covered at 99K. Like others said, ecu's are reliable once in use. On "normal" cars it is usually possible to reset the main ecu by disconnecting the battery, sometimes it takes an hour. On the 07 II, not sure what needs to be done to reset all the ecus or if it is possible even.

I would be suspicious of the diagnosis, and make sure it is the problem and not something else caused by the oil change shop. The air filter idea sounds odd, even if the filter is not there, there are no sensors telling it isn't. It may be grossly overfilled with oil, or some other blunder like pulling a connector off.

 

Much more likely to be P0A0F, P3193, P3190, P0171. There is no code P040F or B3193.

P0A0F is reported by the HV ECU and indicates an engine start problem reported by the ECM, so check the ECM codes. P3190 is Poor Engine Power, P3193 is Fuel Ran Out, P0171 is System Too Lean (Fuel Trim).

I'd start by filling the tank. If the engine still won't start, then investigate air leakages or blockages - make sure that engine air filter is properly installed.

The full diagnostic tree before reaching the 'I do not know' step - replacing the ECM - is quite long. Um, posting the whole P3190/P3191/P3193 section is fair use, right? See the attached PDF.

 

This is just idle speculation, but what would happen if the technician disconnected something like the MAF cable or the throttle control cable? I imagine that would play havoc with the engine. But would the ECU be smart enough to know that those components were at fault? Or would it just throw these codes which indicate that the engine isn't running properly?

 

I agree with Mike's suggestions. After that is done, if the engine ECU is still found to be at fault, I would ask the tech whether it is reasonable to reflash the ECU with the latest firmware first, rather than replace the ECU?

If the MAF was disconnected a DTC should be logged. The electronic throttle also has DTC related to it.

 

Start with the simple gross stuff: check the oil level yourself. I would not even assume that the dealer has done this. What is the level now?

General good advice: always, always, check the oil level yourself before driving away from every oil change, no matter who did it.

 

Yes, there have been cases where it's taking awhile for an oil overfill the gum up the works. It baks up into the throttle body and really causes alot of problems. Checking the oil level would be the first thing to check.

 

Although this may be true, it is possible that the ECU memory storing the firmware became corrupt. If the firmware is downloaded again (even if same version as original) then maybe the ECU will resume its proper functioning (assuming that it is currently inoperative.)

To provide an example, the firmware on my 2004's engine and hybrid vehicle ECUs was updated by a Honolulu dealer at the time that the SSC was released a few years ago. This past summer I had driveability issues. My Tucson dealer downloaded the firmware to those ECUs again, and that resolved the problem.