Immobilizer - where is it? How can i poke at it?
 

Hey all, iv read the wiring diagram but im pretty un-educated when it comes to that stuff, ive searched the forums and havent found anything on this.

Where is the immobilizer? Is there any way i can poke at it, check it, ect..

My car cannot contact the ECU using the OBD2 port scanner and im thinking its the immobilizer because i read in a different thread that someone else had a working car but when the immobilizer kicked in it did not try and crank over.

My engine also will not even attempt to turn over. This is after a massive wreck though.

First thought is to ask if the harness was damaged in the accident.

If you don't know are not sure, I would suggest that the body/chassis harness is closely examined, as are all of the grounding locations.

If they did paint work under the hood, could have a bad ground. As odd as it seems, I had this happen to a car I was working on where the engine bay had been resprayed while a motor was removed.

The relay box was banged up pretty badly in the accident. I have pulled it all apart and inspected it pretty well and it looks ok. It cant hurt to go over the grounds again. Kinda embarrassing but just at first glance i couldnt find where the relay/fuse box tries to ground to the car, but i can look tomorrow.
Its pretty strange, there are 5 high gauge wires running into the box, 3 white and 2 black. And all of them carry 12v, i thought the blacks would be ground, but apparently they're not? At least that's what testing them physically and my very limited understanding of the wiring diagram told me.

unfortunatly its not like the old days when you could jist bypass the imobiliser or remove it.

These days its digital data communication. All the control units talk on a CAN buss (control area network). The dash cluster, imobiliser module, engine control unit, and the key module rf id tag all need to talk to eachother and exchange data before the car will start. If the little key symbol on the dash does not go green you $h1t out of luck and the car will never start.

You next problem is you cannot just swap out those components as they are digitly keyed togeather and any new component needs to be security synced or again car wont start.

Hopefully its just a problem with the CAN buss connections or power to the various modules, else its going to get complex and expensive.

The obd port also needs the can buss to be working, it also has its own supply fuse. I beloeve the obd diagnostics should still work if the imobiliser is damaged or not their as this is how the service guys diagnose problems

thanks, lots of good information, let me go over a few things.
Maybe i dont have an immobilizer problem. Is it possible to tell by just watching the key light in the dash? My key icon goes solid green when im sitting in the car with the key and press on the brake pedal.

Id like to learn more about how the CAN buss connects to the ECU, but thats probably very complicated.

The OBD port does work, daignostics work but the only code its throwing is that it cannot contact the ECM/PCM

I suspect that the error cannot talk to ecm\pcm is comming from the scanner itself and not the car its just saying no communication with anything as the scanner want to talk to the ecgine control unit or other control unit in the car and cannot.

if they key symbol is going green thats good means key code is being read by car

I looked into the CAN BUS stuff extensively. Here's a crash course:

The CAN BUS is a masterless network comprised of 2 coterminous wires that connect to every ECU in the car. There are many ECU's, all of which share data across the bus. The gauge cluster is it's own ECU, the wireless key is picked up by another, separate ECU called the "certification ECU."

(To clarify: Electronic Control Unit not Engine Control Unit.)

If the key icon is flashing green, good and bad news. The CAN BUS is still intact and working.

Bad news: Just because the key flashes green, does not mean the engine ECU is working.

The fact that the key goes green means that the car likes the key and the Certification ECU will not immobilize the car via the CAN. Therefore, unfortunately, the immobilizer is not your problem. Keep troubleshooting.

thank you very much for this.

reading over this again real quick before i head off to work, since the CAN bus can talk to the Certification ECU, but aparently it cannot talk to the ECU ( engine control ) or is that called ECM?
Anyway the engine computer, should i be trying to find that can bus wire and tracing it to the ECU? Or is there a way to test if the ECU is just plain dead?