Looking for some insight into this issue
car is a 99 c5.

Car will not start, turn key just hear the security relay click. security light will just keep flashing.
gauges do not function, radio will not turn on, power locks work but not the windows. Hvac control does turn on though. If you turn the head lights on the dic lights up but will only display the odometer.
tried to scan it and it will not connect to either the bcm or the pcm. Came up communications failed.

We just did a bunch of work to the car and when a friend was hooking up the power wire for the meth kit, he hit the live IGN power wire and it sparked. I'm guessing the BCM is cooked, and I already ordered a new one. Just want to know what else I should look for when I go back to look at it this weekend

(already tried the shaking the door harness, which worked once for about 10 seconds just to roll the windows back up)
but since then it's been DOA.

already checked every single fuse for the car and none were blown.

any help would be greatly appreciated as I"m going to be buying the car this weekend and would rather drive it home then tow it lol

thanks in advance

 

A large majority of communication issues are a result on the doors and driver seat creating a corruption of the serial bus.

Try this as a first step since you can't pull DIC does from the dash.

Look into the passenger side fuse box area. To the left of the fuse box and BCM you will see two Star connecters for the serial bus. One with 4 wires and one with 9 or 10 wires.

Pull the top off the one with 4 wires which will separate the doors and seat from the serial bus.

Let us know if this helps or not.

Here is what it looks like. When you take the top off you can see how it ties all the circuits together and why removing it works.

If you need to discuss anything just PM me with your number.

Mr. Sam









Star Connectors

 

yup tried that already did nothing but will look at it again this weekend while I'm waiting for the guy to come flash the new bcm. Car's been dead for about 10 months so far. Been trying everything I can find on electrical issues on here. I'm hoping it's just the bcm is cooked as that's getting replaced this weekend.

 

Make sure the battery is fully charged to at least 12.6 or 12.5 volts. Low voltage can cause No Comm issues.

Could also be the contacts in the TDR relay even thought the coil is energizing. Having the TDR actuate at least means the BCM is working that circuit correctly.

If it is not cranking at all, possibly the starter is bad or a bad connection there, very common.

Are you SURE it is the TDR relay that you hear and not the starter solenoid?

 

its coming from the relay, if I jump the relay the car will crank. fully charged the battery again before I put it in the car this past saturday was showing 12.6v.
but nothing works in the car at all except the door locks hvac and head lights.
no dic, no gauges, no windows. turn the key hear a faint click from the footwell and that is it.
I'll shoot you a pm with my number though, wouldn't mind discussing with someone else, hopefully find something small that I overlooked already. But I"ve gone through pretty much every electrical and bcm related thread on here over the past few months with no success, hoping new bcm will solve the issue.

 

You are talking with the right man...call dadaroooooooooooo!

 

definitely sounds like it, I most definitely will.

 

When you guys get this figured out...Please come back and explain how, what, why you did to fix it...Thanks steve

 

will do, hate finding threads with the same issue as I have and they just dead end with no explanation of what the fix was.

 

DID you check the FUSES for the ignition switch power??????????

This is a 99 C5 Ignition Switch circuit:

 

bill I've pretty much read everything you've posted on here electrical wise (many many thanks for your hard work on that).
and yes I've pulled and checked every single fuse in the car, more than once lol.

But just for my own curiosity I'll go through them again with the diagrams when I get back to the car this weekend. since it was about 6 months ago that I went through them.
really would like to drive this thing home, hate to have to tow it 100 miles.

 

Check each fuse test points to ground with a meter to insure you have proper voltage on both test points.

Bill

 

will do, bringing my test equipment with me this weekend to see what I Can find. now just need to find someone mobile to flash the bcm. guy I was going to use doesn't travel out to nassau county where the car is.

 

There is an emergency on the road BCM/PCM sync procedure that you can do your self. It will get you home without an issue. I dont have it here at home. Its at work.

Maybe some one can chime in with it.

Bill

 

if someone could post that up that would be great. I have a dealership right by my house I could always take the car to to have it flashed if I could drive it.

really hoping to get this thing going saturday, it's too nice a car to be sitting like this.

 

well found your post on it


Im trying to save you time and money. The BCM and PCM are NOT plug and play modules and must be programmed using the tech II/ There is an Emergency Sync procedure that you can use if you have to install a BCm on the road with out a TECH II:
-----------------------------------------------------------
BCM/PCM RELEARN PROCEDURE


You will need to conduct the PCM/BCM relearn process. This matches their handshake ID's and allows them to talk to each other.

Do this before you worry about VATS issues:

1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.

The car should start and run with the new BCM. Good luck and report back on your progress.
Shirl
SD Racing Enterprises
Aguila, AZ
Coutersy of MrEracer


This will sync the PCM to the New BCM but all of your RPO options will not be retained. You will need a TECH II to program them into the new BCM.


If that doesnt work, Unplug all un necessary modules ie: Door Modules, Drivers seat Module, HVAC module, RFA Module, etc and see if the issue goes away The ONLY modules that you need to start the car is BCM and PCM.

If you isolate all those things, it will tell you if some other module is causing the issue:

BC

 

 

Found a dead short on the orange wire at the ignition switch to the 40 amp maxi fuse in the in cabin fuse box. Tracing it now.

 

You go blood hound on that thing

 

well we traced it back to the under hood fuse block. if we left the block (harness goes into that plugs underneath fuse box) loose the grounding out was gone, but still nothing worked as soon as we tightened the bolt down holding it in, it was back (continuity with chassis).
it's the heavy orange wire running from the ignition switch to the in car fuse box. if we disconnected the harness from the block we didn't have continuity to chassis ground) So hopefully it's at least not something melted in the dash, so I don't have to rip the rest of it out. But that line comes in the center block of pins and it seems the short is in the maxi fuse side of the box. but we were working on 2 cars friday night until 5 am and running on 3 hours of sleep so we decided to call it quits there.
btw dont ever try to swap injectors in a subaru it's literally a 5 to 6 hour job when conditions are ideal, however working outside in near dark and rain it took us 10 + hours including the fuel pump which of course being half asleep forgot to put an o ring on the pressure outlet. always nice to finally put something together at 3:30am and try and start and nothing happens.... 26 hour long day with an ending of crushing defeat lol

guess I"m going to try and find another underhood fuse box and swap it and see if the dead short goes away. or at least be able to rule out the box as the culprit and keep tracing it from there. Probably go back next saturday for a few hours and mess with it some more.
if we get it tracked and the old bcm still works, I'll have a spare 99 bcm if anyone needs one