Hi Im working on ford mondeo mk4 and so far discovered that there are multiple communication faults. Checked the resistance, voltage… On osciloscope can high and can low are good but occasionally the network spikes and also the relay of glowplugs starts clicking for few seconds. This happens at rand…

Are you saying that on your scope screen can hi is a clean square wave between 2.5 and 5 volts and can lo is a clean square wave between 2.5 and 0 volts? And then network comm spikes or becomes erratic? If so that suggests a wiring issue, perhaps water intrusion or an intermittent short like wiring…

A faulty battery could cause those symptoms. It might measure the correct voltage w/no load, but might go too low during cranking and confusing the computers. Suggest to start with battery/alternator functional test.

When the relay starts to click(at random time, or when i close or open door) this is what it looks like on osciloscope. After spike comes few seconds dead line at 2,5V. The images are on different site, could not upload them here. [image] Snímka obrazovky (1) — Postimages …

But why would it shorted only when the door is opened/closed. Or every few seconds. Could it be module itself? Or some other thing that sends false information to module and then module is doing wrong things. The are 3 network. Problem occurs in modules that are in can netwrok high speed. I tried to…

I think Ford Mondeo was called “Ford Contour” in the USA . . . but we didn’t have the diesel engine option

[image] db4690: I think Ford Mondeo was called “Ford Contour” in the USA . . . but we didn’t have the diesel engine option +1 That model was originally intended to be Ford’s “world car”, but they wound-up making a LOT of changes that made the European version very different from the US versi…

[image] dianiskatomas_191452: when i close or open door A somewhat common failure mode is when the wires going between the chassis and door fail from repeated bending/flexing. This can result in broken insulation and shorting between the wires and/or ground. I don’t know your particular car b…

No communication between modules/car wont start

Maintenance/Repairs

davesmopar May 11, 2026, 1:01pm 14

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No communication between modules/car wont start

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