ABS warning lights after catalytic converter replacement

It may not be the mechanic's fault, but damage that was missed when the thieves stole your CAT. Everyone was concentrating on the missing CAT and nobody did a full inspection of the undercarriage. Thieves could've done some damage when jacking up the car to steal the CAT, the shop could've damaged it when they jacked it up, or you could've ran over something that ripped down something down in the ABS system.

Good Luck.......

 

We need to start by asking the car what it thinks the problems are.

If you don't have a suitably-capable scan tool for doing that, then do this:

Blink (a/k/a Flash) Codes – How to. | PriusChat

Once we know what problems the car is reporting, we can reason about whether they were likely caused by the mechanic, or by the thief, or by something else.

Whatever the answer to that is, we will at least know what it is that needs to be fixed.

 

... which is a sign to proceed cautiously, because in a gen 3 car the "booster" and the "accumulator" are different parts.



The detection conditions are either the accumulator pressure doesn't rise at the expected rate when the ECU has turned the pump on, or that the pressure falls faster than it should while the pump is off and the brakes aren't being used.



What do your ears tell you about how often / how long the pump is running? A pump that runs and runs, without the pressure building fast enough, is one kind of explanation. A pump that doesn't run when the ECU tries to turn it on is another kind of explanation, and a pump that has to keep cycling on and off because the pressure falls quickly between pump runs is still another kind.

You can see the "Trouble Area" box concentrates on the booster (top thing in the drawing above) as the likely suspect (it has the most internal valves and seals to possibly go leaky). But there are three pages of troubleshooting steps for that code, and you can also end up at the accumulator/pump (bottom thing in the drawing) as the culprit sometimes.

Probably the cat converter replacement didn't do this.