ASLLCH

The backstory is sort of long, but a friend's beater 2000 LS hatchback got messed with and they're basically fed up and gifting it to me, provided I can get it going.

A thief smashed out the ignition switch core, moved it a block away, and stole the battery. We live in a big city where weird crap like that isn't unheard of; cars will get jacked to run some illegal errand or another then left back in the same neighborhood they were stolen from. We have a large homeless population so the battery was probably taken to power stuff in someone's camp or something.

So I get a new battery in it and find a used ignition switch w/ key. Full unit w/ immobilizer hardware attached, etc.

Defeated by the immobilizer, won't start, flashing green key indicator on dash.

The thief left the old switch-side immobilizer box intact, basically, and patching that in, using the new key to turn the switch while holding the old key (red, Acura original) to the old immobilizer, still no luck.

Battery is brand-new and fully (manually) charged, contacts are cleaned and tight.

Behavior is as expected from an immobilizer issue, starter goes to town but fuel pump doesn't engage.

It had been running fine before the break-in, but has seen way, way better days cosmetically, so I want to take it on as a project car without investing a ton of dough taking it to a dealer or whatever to sort this out.

So right now, reading other threads, I'm seeing my options as:
- break the immobilizer chip off of the ECU, hopefully get it started so it can at least be driven, then get an aftermarket bypass chip so it can pass smog. No codes thrown with the bypass chip, right? The Mobilizer FX-01 or something?
- Instead of a bypass chip replace the OBD2B ECU with a P75 OBD2A, there's one on eBay right now for a '96 Integra LS automatic. Should be fine, right? Why are OBD2A to 2B conversion harnesses so freakin' expensive? Seems like a racket?
- Junk it for parts, which is what my friend was about to do before I decided to take it on. They barely paid anything for it and they don't need a car for their work commute.

Any thoughts? I'll probably break the chip off anyway so I can at least start the engine, any red flags with later swapping in an OBD2A P75 ECU to keep it moderately legit and error-free? I'd rather do that than the chip swap. Are the harnesses between the 2A and 2B really so different that I need to buy one, or can I just swap a couple of pins around?

If I'm defeating the immobilizer one way or another and keeping the thing I'll be patching in a fuel pump kill switch somewhere discreet, basically serving the same purpose.

For some Hondas, I see that there's some immobilizer hardware on the plastic panel above the knees, driver-side. In this Integra, there's a small black box with a square blue button on one side in a similar position, what's that thing?

The other, obvious question, which no one will want to answer publicly: how the f**k did the thief move this thing with the immobilizer engaged? There was a length of wire on the floor; they'd ripped the plastic off the steering column but left the piece above the knees intact leaving most of the harnesses covered-up.

Wish I knew what the problem was without having to do any of the workarounds.

ASLLCH

Also, if someone wants to explain how the immobilizer works in general... basically, I'm assuming that the black box above the ignition switch acts as a receiver and sends the OK to the ECU, allowing the fuel pump to engage. Is the same ID in the key's chip registered with the ECU? Is that the problem here? Need to reprogram something in the ECU beyond just replacing the full ignition switch w/ its native key present?

Tjw149

Try using the new key with the locking cylinder with the original mobilizer box plugged in. Then try to start the car with the original key right on top of the new key. Use the new key in the cylinder but keep the other directly on top of it. My buddy does this to start his e46 because the dam locking cylinder was so worn he had to replace it. It takes him about 5-10 minutes to start his car like this. This method works on old BMW's I'm sure it will work on a Honda.