Just had inverter coolant pump changed, ran 1 day, now not starting, getting P3191

It is pretty hard to mess up an inverter coolant pump remove and replace and should not result in a P3191 if something was done incorrectly.

The diagnostic and repair process for a P3191 is pretty much the same as for any gasoline engine.

 

Generally speaking I would say not but I don't know that 2003 model that well that's the little coupe thing. Generally you go over all the ignition related stuff and are you sure you're not out of fuel that will certainly make the engine not start I've had it happen to me on purpose about three times I do this when I get a new car and do a gas mileage test I run the car out to empty to see where my fuel gauge actually looks like when it's empty and how far I can go after empty.

 

i wonder if he might have bumped some other wires?

here's a thread:

code-p3191.77997

 

Before jumping into engine diagnosis, which this could be, check a couple of other things first.

Turn the ignition to "acc" but don't start the car, then test the 12v battery voltage. It has to be above 12.1v in acc in order to be sufficient to booting up the system to start the car properly.

If good, disconnect the 12v battery for a few minutes then reconnect it.
This will reboot the ECU system and allow it to better recalibrate to the recent new changes in the system, and allow the engine ECU to start the engine properly.

SERIOUSLY, try this first, It may save you some effort and trouble.

 

Well, believe it or not, couple of mornings ago when it was single digits outside, I read 9.6 volts on the ScanGaugeII and the hybrid system booted just fine with engine "Ready" in about 1-2 seconds. YMMV!

 

OP, I'd forget about the coolant pump. That's not your issue. Maybe it's an issue, maybe it was never an issue. It wouldn't cause a cold engine to not start. The car would have started and run just fine after your tech's work regardless. A failed pump will only affect engine performance once the inverter coolant temp gets too high, which it doesn't do real fast from a cold start.

You got another problem, or maybe one that was only ever your problem, IDK. The first clue, IMHO, is that you're not getting other codes. That generally means problems in components that are not sensor-monitored, more "mechanical" than electronic. Fuel delivery can be an example, or the throttle body.

Of course, check the basics - does the ICE rotate? Got oil, fuel? It's possible and fairly easy to slightly lift the fuel rail off the injectors to see/confirm base fuel pressure. Should see if when you first lift, and then turn the key on a second to reconfirm before sealing it back up. Does risk the injector o-ring(s) failing when you set it back down, so be careful. Definitely check for loose connectors on any sensors that might be telling the ECU to not energize or push fuel.