Little while ago i noticed that, after some diagnostics, the ecm is making ALOT of em interfierence in my electrical system. Enough to cause the head unit not to receve stations or function correctly. On the stereo the interfierence is most pronounced around 92 MHz. Anyone have any ideas as to what might be causing this? Possibly it might be a bad power transister? Id like to salvage the ecm if at all possible.

 

That's a new one.
Are you sure?, about the only thing I could see if feedback from the ecm being poorly grounded, and spiking the system.
HTH

 

 

Im 99.999% positive that its teh ecm or something directly related to the ecm thats causing the problems. Unplugging the ecm fixes all of the the em interfierence. Im not at home right now but when i do get there ill double check the grounds. I did have the car in the shop for four new tires just prior to having this problem. I specificly told tehm not to poke around the car but its possible that maybe they knocked something loose.

 

Since the PCB is grounded to the case of the ecm ran a ground to the ecm's chassis and directly to the negative terminal on the battery. That really made things worse. Blotted out all the stations on the stereo with a continous buzz. Surprisingly, if i grasp the metal case with both hands, the em interfiernece is damped out by my body and I can no longer hear it in the stereo. I guess its time for a new ecm but what went wrong? Somethings obviously leaking to ground.

 

These are initial thoughts. . . The ECM is grounded to the engine block. This allows the sensors to return ground directly to the ECM. As far as I am aware the ECM does not have a ground to the chassis/dash/frame, only the engine.

It is possible that there is a grounding problem elsewhere. Check the battery ground, firewall ground straps and such. See if any are loose or melted.

Strange problem to say the least. It is as if everything electrical needs to be checked. Kinda' like in a poke, tug, prod sorta way.

RBob.

 

Its rather cold out so ive only given things a cursury look but ill have a more thorough look at it.

 

Dont know if there is any confusion on this but when i ran the ground, it was from the ecms case, which is grounded to the printed circuit board, to the front strap that hookes on the cylinder head.

 

checked the ground straps, theres no problem there. Both the two at the rear of the cyl. head and the large main strap at the front appear to be sound and corrosion free. The battery terminals are clean and completly free of corrosion. I guess ill go buy another 8063 or an 8746 and do a substitution test. As for the interfierence, it appears to come directly from the ecm itself. I ran it w/o the enclosure (engine off) and the intensity changes as i hover my hand around the board. Its the wierdest thing. It appears to be coming from possibly the processor as its tied in with the presense of the prom.

 

When you figure this problem out I'd like to know what is causing the interference. Sorry I couldn't help any.

 

Got the 8746 in the mail today and swaped it in. As luck would have it the injector driver in the ecm is completly dead and the car jsut cranks. Doesnt really matter, anyhow since it still had jsut as much interfierence as before. Im at a loss... I checked everything and cleaned all the grounds and still the problem persists. I had a remote mount switch for the prom and the EM interfierence was bad enough to cause the ecm not to read the eeprom and it would go into limp home mode. This whole problem started right after one of my tires came apart and I had to pull into the nearest service station for repairs. You dont suppose they could be related, do you? It wouldnt surprise me one bit if there was something they did to the car. I guess ill jsut have to live with it. Ive checked jsut about everything and still no luck.

 

The last thing I can think of is to pull all but the most esential pins (grounds/power/SES lamp) out of the connectors for the ecm and if that stops it, then add each circuit in one at a time to see where the problem is.