2001 P3191 Problems

I suggest that you try the following:

1. Ensure that your 12V auxiliary battery is in good shape by charging it. Open-circuit voltage should be 12.6V or greater after the car has been IG-OFF for a half hour or so.

2. What is the odometer reading on your car? If the iridium spark plugs have not been changed recently, I suggest you change them. Change the engine air filter while you are at it, if dirty.

3. Clean the throttle body interior and throttle plate using throttle body cleaner rated safe for use with catalytic converter-equipped cars. Those surfaces tend to form black gunk, probably engine oil residue from the PCV valve hoses. When the car is IG-OFF you can rotate the throttle plate 90 degrees so that you can clean the underside.

The point of doing the above is to ensure that your car's engine is in basically good shape. Since you have TSB EG011-03, you know that the first step is to rule out these maintenance-related issues.

The TSB suggests replacing the engine ECU, not because the old one failed, but because the most recent revision allows more time for the engine to start before the ECU gives up and logs an DTC.

The fuel tank and circuit opening relay replacement is suggested if your fuel pressure is low. Did your dealer actually measure the fuel line pressure which should be 43 psi or better?

You can test the relay yourself by prying it out of the relay box, using a ohmmeter to identify the coil terminals vs. the switched terminals, then applying 12VDC to the coil terminals and measuring the resistance at the switched terminals. If the resistance is more than 0.2 ohms (after accounting for the resistance of the ohmmeter leads) then I suggest replacing the relay. It is located in the relay/fuse box near the inverter.

After you have done the above, disconnect your 12V battery to clear the accumulated DTC and start driving the car. If you still get P3191/P3101 codes, then see if you can buy the current model engine ECU 89661–47054 at a salvage yard (the TSB also provides this part number.)

As to the other codes that were logged, they might result from poor engine power and a drained 12V battery. Ignore them for now and see if they come back after you've performed the work above. P0420 indicates a failed catalytic converter, which will be another expensive repair.

You can find a complete list of Classic DTC codes at:
http://www.ecrostech.com/Products/MiniScanner/UserManual.pdf

Good luck.

 

This is why as a mechanic I am not a fan of diagnostic codes. Too often people read the code as the whole problem and don't see it as an indicator of what might be wrong. For example something we saw frequently was a code for exhaust gas oxygen sensor out of range, replacing the O2 sensor didn't fix the issue because the real issue was a broken manifold stud which allowed oxygen into the exhaust.

I'm with Patrick Wong on this, do the maintenance items then see how it goes. It does sound like the ICE isn't starting in the time allowed so making it easier to start may well sort it. Quite a few on this forum had had issues which are caused by an old, tired 12 volt battery so testing that makes good sense.

Yes, I know I added exactly nothing but I felt I needed to add it.

 

These instructions should help, Cleaning Prius Throttle.

Bob Wilson