2007 Scion tC questions
 

Hi there. I'm new here, so if this violates any forum rules or if it's in the wrong place feel free to delete it and send mean emails to me. :)

I'm hoping someone can point me in the right direction with a couple of issues; outside of minor maintenance and upkeep, I don't know much about cars. I've looked for answers but can't find anything. I took my car to a mechanic last week because I thought my alternator was going out. Turns out the previous owner had installed an aftermarket alarm system and it shorted out, causing it to drain the battery. The shop removed the alarm system.

While driving home after picking it up, both the airbag light and check engine light came on. When I got home and tried to lock it with the key fob, I found that it had stopped working. I took it back the next day and they told me the airbag sensors in the seat belt and passenger seat aren't working and that the check engine light is on as a result of ignition coils and spark plugs needing to be replaced. Again, I picked it up and drove home. This time, I noticed that, in addition to the previous issues, the tachometer didn't work, the lights on the dash that show what gear it's in doesn't light up after neutral and that the sunroof switch no longer works. My OBD scanner said the light was on due to a transmission sensor, as did my coworkers. I even changed the plugs and coils yesterday morning, reset the light and it came right back on.

There's no way all of these things just randomly popped up, right? I mean, these problems didn't exist until they worked on it.. Is there anything I can check/look at to determine if it's an easy fix? Taking back to the mechanic is out of the question. They're not owning up to the fact that this only happened after they messed with it. I'm just a bit lost on what/where to look.

i think it sounds to me that when they removed the security system, they either cut a wire they shouldn't have, or they didn't reconnect a wire they should have...

I'd get an alternator test, then take dogg's suggestion and look for errant wiring. If you're still on business terms with the questionable mechanic, ask them to explain whether they ran into anything unusual when uninstalling the accessory. Ask whether existing wires were spliced or cut. If your stock wires were spliced, I'd cover any bite marks with electrical tape. If your stock wires were cut, I'd check that the color codes correspond at every cut. Might also check the ground point where the accessory was grounded, just in case the mechanic ripped out more than he was supposed to.