No communication with ECM

Reply Subscribe

Thread Tools

Search this Thread

Jun 2, 2024 | 02:55 PM

Prozak

Thread Starter

1st Gear

Joined: Jun 2024

Posts: 1

Likes: 0

No communication with ECM

Hello all, I'm having a strange problem. The truck runs and drives no problem. No lights on the dash however they do all come on like normal when I turn the ignition on. But when I try to plug a scan tool into it I get absolutely no communication. All fuses are good, I double and triple checked.

I suspect it has something to do with the 101 pin on the ecm which I believe is responsible for giving a ground to the glow plug relay, which caught on fire the other day, which launched me down this path to begin with.

For now I just disconnected the relay so I have no glowplugs.

Jun 2, 2024 | 03:52 PM

udsuth78

Lead Driver

Joined: Oct 2005

Posts: 6,129

Likes: 1,919

From: Ponca City, OK

What exactly caught fire on the glow plugs relay? The large hot lug comes straight from the battery. The hot side of the coil is fed by the PCM relay 87 pin so basically if the key is on it's powered. Then like you suspect the PCM provides the ground to the coil to control relay function. The most common cause for obd communication troubles is a blown fuse. The obd port shares a fuse with the cigarette lighter so not uncommon to see an overload on the circuit. I know you said you checked, but did you heck with a meter or visual? It's not uncommon for a fuse to look good and test bad. That said there was a recent thread with similar trouble. I'll see if I can find the link. It might have some helpful info for you.

Here's the link

https://www.ford-trucks.com/forums/1...mmunicate.html