On my 1993 RR LWB 4.2l there is a 5-6 inch wire coming from the negative side of the ignition coil that goes to ground and it has a small diode on the wire. I don't see it showing up on any wiring schematics. Is it supposed to be there? Does anyone else have it on theirs? This is not the resistor on the wire back to the ECU. I have a no start problem and am just wondering what this diode is doing here.

 

I think you are referring to the capacitor. It's a small cylinder meant to suppress noise. You can disconnect it and continue on with your diagnostics.

 

No. I should have ruled that out in my original post. The capacitor is there but on a different wire is a tiny diode about 1/10th the size of the capacitor. I'm wondering if it is factory or not. It was covered with hard rubber so before I peeled the rubber I didn't even know there was anything there.

 

It maybe a fusible link, not like a normal (in looks) fuse but will blow to
stop a over load.

 

Well it's definately a diode. i WENT TO rADIO SHACK to buy a new one and they have them listed as "rectifier diodes". Same # on it.

 

No diodes are factory there. Is there a wire attached to it? May be some sort of alarm system.

 

The wire goes from the negative terminal of the coil to ground on the fender. It is about 6" long. Thats it, just a wire with a diode..........

 

Did this ever get resolved? We're trying to replace what appears to be the same device (ERR4019) which is quoted as a diode. I think it's a zener type to protect against back emf damage.

 

It's a small cylinder meant to suppress noise. You can disconnect it and continue on with your diagnostics.