hey guys hope u can help me out here,as i am just about done with my gmc syclone project i figured i needed a toy so i bought a 99c5 from the auction now here are my problems ,i picked the car up and every light message on the dash was on abs traction reduced power airbag etc.so i brought it home checked all the grounds etc and ohmed out all the data lines in the whole car and checked for corosion on pcm bcm etc.So i tried to hook up the scan tool and i have no connection to anything abs bcm pcm airbag nothing i checked the obd2 port for pwr and ground all is good,nothing in the car works either no radio no heater display no fog lights no ac request no windows locks ,but the car runs and drives great i also have no gauges just tach and voltage,So i had my buddys from the local chevy dealer come over and put the tech 2 on it that wouldnt comunicate either ,so they brought the ecm to the dealership and it was a remanufzctured one and it had like 125 codes in it but they said it looked like someone tried to clear and relfash over it ,they are thinking that the pcm is so messed up it is making the bcm screw up that bad and they also think maybe i should replace both the pcm and bcm,i mean all this stuff is controlled by the bcm on data lines right?so what do u guys think ever heard anything like this?both computers are under 500 bucks which isnt bad but i hate to spend it and not be it,but what else can it possibly be,thanks brian,oh and i seen some say about a seat module this car dosent have the sports seat memory seats i dont think they are the ugly one piece ones so do they still have a module that can mess up?

 

I would start with the pcm.
Was this a flood car.
what has been removed?

 

it was suppose to of been a flood car but the guy told me it only went just over the bottom of the rim which i belive becasue i have seen my fair share of flodd jobs,there are no traces of water corrosion etc,i was going to order a new pcm and bcm;.

 

Salt Water is death to a car operations. Corrosion damage starts everywhere no matter the water level. Corvettes have a electrical system that will not react based on the flood initial water level.

 

yeah there are no signs of sALT OR water no place that i can see

 

Pull passinger side wheel and fender liner look at the pcm.
How does it run?
Sounds more like the bcm it has noting to do with seat module.
If you have one of the data bus wires grounding it will cause dash and gauges to go dead.

 

we checked the pcm it is clean and dry but it is a reamnufacutred one so who knows what flash is in it,it runs great but every light on the dash is on and reduced power,and nothing in the car works radio heater fog lights traction switch windows etc but it runs great,and the gauges also dont work ,just the tach and alt im guessing because these arent data line feed?so a bad seat module or door module would mess it up that bad?And also i cannot get a scan tool to link to anything in the car pcm bcm abs airbag and i have 12 volt a ob2 and good ground,and i checked all the grounds on the car and they are perfect nice and clean,i hate to buy these modules and it not be it but i dont think i have a choice thanks brian but if the pcm or bcm is bad the data lines could be shorted thaty is why i cant get a communication with a scan tool?

 

Sounds like someone already tried to fix go thru all of the frame grounds if a ground has issues it will cause this.
Does the BCM have oxidation on it?
Have you checked the connector on the pcm?
Remove PCM and reinstall take note as to the condition of all the connectors. Are you sure the PCM is from the correct year?
What electronics do not work?
Can you access codes thru the DIC.
Is almost sounds as if the car was sabotaged to make the insurance total the car. The low water level story doesn't jive.
My suggestion is start eliminating circuit's the engine runs so it has to be somewhere in the data bus. I would remove and inspect the pcm first.

 

i wlll say for sure water did not get into tghe car for sure yes i did check the bcm and the inside fuse box everything is clean perfect no corrosion of any kind at all,i didnt try to access any codes as i dont know how to in the car,but i did try to put the scan tool on and i have no communication with anything abs airbag pcm bcm ,as far as what dosent work see my post above thanks for the help man if the pcm is bad it would affect all the other inside circuits?im guessing maybe it can be shorting out the data line ?

 

What method did you use to check the BCM??????

My BCM looked like it just came off the GM parts shelf but, when I took the circuit board out of the silver box,,, the back of the circuit board was covered with a white oxidation.

I used a soft brissel brush and some alcohol and removed the oxidation and got it to function normaly. Then I needed to remove the HVAC blower motor to clean out the air box (without removing the fuse first) and touched the motor to the BCM by accident) The resulting electrical arc killed the BCM! (The housing on the fan is at +12 VDC)

So,,,,,,,,,,,,the board inside the silver box could still have issues!!!!

BC

 

bill i see u seem to be the guru i have a electrical shop here in ny and i have checked everything that i know off and i dont hacve a tech 2 but i did take the bcm apart and it is perfect nothing on it at all,any ideas nothing in this car works but it runs great thanks brian also my friends from the dealership came over with there tech 2 and theres or mine will not link at all to the car

 

I think it is pointing to the comm link between bcm and pcm.
I have seen something like this once it was a botched pcm install.
Three pins were unseated and bent in the pcm connector.
I really sounds like someone tried to fix and hosed something up.
Call Genes car shop for a used pcm and bcm. It is electrical but where is unknown at this time.
I have seen where the door harness connectors working loose and cause the dash electronics to go crazy.
Any after-market electronics in car?

 

no aftermarket stuff at all i checked the door wires and they are mint all the connectors at the oraNGE HArness also i ohmed all the data lines out from pcm to bcm to the modules and seem ok ,my buddy works at a local dealer and he told me 420 for both computers ,any ideas?

 

How did you examine the Chassis Ground connectors??

Are you SURE that you examined all of the grounds?? There are also SPLICE PACKS (SP's) that could also be causing trouble. They are located all over the car. The two that come to mind that can effect this problem are in the passengers foot well and in the passengers side just aft of the battery near the fire wall.

Here is a picture of one that was exposed to a battery acid leak!



Here is an example of a good ground connector:



Do me a favor, recheck your DTC Codes using the OBDII Self Diagnostics system built into the car. report all of the codes and make sure that you clear ALL of the ones present. Then check to see which ones come back.

If you stick with me,,,we will figure this issue out!!

BC

 

bill great pics ,i did check both ground spots u are talking about and they are perfect ,maybe i can give u ring and i can tell yah what i have tried i really dont want to give up the car i like it thanks brian

 

Check PM for fhone number. Give me a ring.

BC

 

bill thanks for the help tonight i am getting new pcm bcm tommorow will let u know thanks Brian

 

well dealer got my new bcm and pcm today i put it in and brought it over to the dealer for them to program it and they said they need a splice adapter of some sort for the bcm,kent moore tools makes it its like part number j42236 or something close i think anyone can confirm what needs to be done for proper bcm programing

 

You should be able to install the two and program with tech2.
If you were close i'd let you use mine.
You should be able to establish link to tool and pcm without programming the bcm.

 

thanks u dont need this splice pack connector?do u know what this is i am talking about thAt they are telling me i need?