12 v battery replacement - won't run

Think your going in the wrong direction looking at the battery voltage. It will probably be ok. I still think maybe circuit opening relay or MAF sensor dirty. Did you have the air filter out by any chance?

 

Hi Rick,

These also are reasonable to check. Not sure whether HOVZOOM has the ability to test the circuit opening relay or remove/clean the MAF sensor.

Going back to basics, a gasoline engine requires compression, spark, and fuel to start. I am assuming compression is OK.

If HOVZOOM can do this, how about removing one igniter & spark plug, then connect the wiring harness to the igniter, ground the spark plug shell & see if there's spark and fuel odors when the car is trying to start.

Another concern is that the traction battery charge may be rather depleted by now. Does the MFD show SOC at an acceptable level?

 

The ice spins, how do you know it starts?

The electric motor will spin the ice at about 1000RPM (Idle speed) with no "starter motor" noises. It will spin for 10 seconds then if the engine hasn't fired it gives up. Can you rev the ICE within that 10 seconds? floor it and see if the revs go up.

 

Wow, I knew my Prius was good but I didn't realize that it was that good!

 

That's great. What is the traction battery SOC now?

I suggest that you drive it at least 30 minutes today and ensure that the car continues to work, before you embark on your weekday commute.

 

Good.

Thinking ahead, if you experience similar symptoms in the future, then it is quite possible that you need a new engine ECU, which allows more time for the engine to start before logging a DTC. The specific DTC involved are P3191/P3101. TSB EG011-03 is the relevant service bulletin on this issue.

For fun, you can try finding the engine ECU which is located behind the glove box. The current part number is 89661–47054. If your ECU has a number below that, then you would benefit from getting the current ECU installed.

If your car has less than 80K miles, this should be covered under the federal emissions warranty. If your car is no longer covered by warranty, then you can try buying a salvage part and installing yourself.

If it is not possible to obtain the current version engine ECU, then you can try tuning up the car as follows, which might improve the engine start time so that you no longer have problems:

If the iridium spark plugs had not been changed at 60K miles, I suggest that you change those now. You've said that your engine air filter is new so you are good to go there.

Test the circuit opening relay (I suggest replacing if the resistance across the switched terminals is 0.2 ohm or more) and clean the MAF sensor with brake parts cleaner as Rick suggested. In addition the throttle body and throttle plate should be cleaned using throttle body cleaner.

 

I used to own race cars & go to the strip. I always went by one rule- if the car is not running right I made only 1 change/adjustment between runs as to find out what happened. You stated that both batteries have enough volts in them. The only other item(s) you changed were the plugs. But, that was 2,000 miles ago. Did the car run fine for the last 2,000 miles? Did you change or perhaps move any electrical wires or perhaps not tighten all your connections? Take back steps & think of anything else that could have been disturbed when you did the battery change out.

It could be a fluke, but electrical systems can be strange as they get older. I wonder if Toyota has a code book & meter you can plug into the diagnostic port of the Prius. My last computer car was a Buick Grand National & I had a code book & meter I bought from GM that helped me isolate hard codes. In this case if you can't find a loose connection or something related to what you did then the dlr. will have to find it for you.

My only other thought is the old battery was good & just a little weak from age. You put a new battery in the car & it wouldn't stay running.You then put the old battery back in & got the same results.

My guess is something got disturbed & is causing the new problem.

 

I may be totally wrong, but if the old battery was weak, and if the new battery was only partially charged...when attempting to start the ICE for the first time, neither one had the lasting current capacity to maintain and sustain the voltage needed for all of he CPU functions to clear. On your last try, the voltage on the new battery may have stayed above the threshold needed to keep the ICE running long enough to charge it sufficiently. I'll let the experts speculate on this theory...I've experienced extreme battery voltage drops during testing while under load conditions. What do the Senior Engineers Think?

 

try turning the key on and off about 8 to 10 times ,this will give the computer time to reset any time i have removed the cable for work being done on car i had to turn the swith on /off to reset.

 

Just curious, while the engine was running, did you try the " Force charge method"? ie: All brakes on, put in Drive, push accdelerator to the floor. This will charge the HV to green and thereby charge the 12V aux. Oops, I didn't notice thread date, Oh well, next time.................