Hi, I started learning about cars so I bought no start ford mondeo mk4 with electrical problem. When the wake up signal comes to the ecm, the ecm starts to always turning on and off. Thats why also other components like glow plug relay, actuators… And so on are pulsating. I have tried many things, grounds, can bus(because ecm is not communicating), measured ecm.
My newest discovery is that i tested ecm on my workbench. I connected power supply, grounds, wake up signal (which goes from body control module) and last one of the pins that are pulsating. In this case it was pin from glow plug coil relay(12 volts go through coil and ecm should ground it, but when i measure at ecu with osciloscope. Voltage is pulsating from 0V to about 3V in matter of miliseconds.) So my test results were exactly how ecu acted connected in a car. The relay was pulsating. That is when you would say, oh then the ecm is bad. BUT. I tried other 2 ECMs and the have all acted like this one. The question i have now is, is there something that I have to connect while testing on a workbench that will wake up the ecm like it should be? That would means something in my car is not fully waking up the ecm. Main ignition relay coil and load sides are good, wake up signal from body control module is also good.
I really want to learn about cars so i chose this hard path, but I no longer have options in my head. Thats why I want to ask you more experienced guys.
Wow!!, most people start out doing brakes, oil changes, lite suspension and steering and basic maintenance, not to many start out trying to tackle an electrical issue… It can even be hard to find a shop that does advanced electrical work… lol
Anyway, this forum is a USA based forum so we don’t get your Ford Mondeo MK4 sold here in the US, much less a diesel version… But just incase, what year is your vehicle??
Year 2011. Well i am certified electrician so i know some stuff, but missing on experience with cars. Thats why i dont know what all input to ecm is needed to fully boot her up. Most of the things i learned myself from internet and my mistakes. I learned a lot, but i feel like im in dead end now.
Every fuse in the vehicle, or just the ones you think need checking?? Check them ALL if not already…
Home vs automotive electrical have some in common, and a lot not in common… as you are probably finding out…
It’s like this, many years ago Hyundai and or Kia ran part of the transmission circuit through the dome light bulb circuit, IF the dome light burnt out, the transmission STOPPED working correctly… You just never know what all runs through what circuit(s)…
Here is a crazy video of HVAC and Radio controls and some other things not working over water getting in the taillamp assembly’s…
Also, you DO have a factory wiring diagram of the vehicle I hope?? Might even require a factory service manual, not owners but service manual..
I am more familiar with the ECM in GM vehicles but the same troubleshooting techniques should apply.
When bench testing the control unit, a visual inspection comes first. Use your eyes and nose. Look for deformed electrolytic caps (top is not flat, bottom is bulging, liquid escaping), cracked or burned components etc.
Next, check all of the bus voltages are present and within specs.
Next, check that the microcontroller has a clock and supply voltages. Look at the brown out input to ensure it is not active (usually a low voltage threshold).
Check schematic for control lines- things like this wake up signal from the BCM. Also, if there is a security input from another module. The GM needs input from the VATS/Passkey module to function properly. What does ford use?
If all else fails and you cannot get a schematic of the ECU, there are refurbishment places you can send it. They can test and fix it, usually for a reasonable fee. If you have a schematic for the unit, perhaps share an image and we can help direct the troubleshootign process…
Just off topic a little but when the CRT went black in my riviera many years ago, I tried getting a schematic for it. No dice. Made by zenith but they only give these out to authorized factory repair shops. Cheaper just to buy from a junk yard.
Same thing with repair of the radio. The delco shop knew what to check, had the parts and only charged about $100.
Biggest problem was finding the shop. This is no place to start working on cars.
