2009 E320 om642
Hello all, I am afraid I may have lost my ECM and need some help figuring it out. First there is a big background with my question at the end of this post. For a week now I have been trying to solve an issue of going into limp mode and codes , mostly low turbo boost followed by many other alternating codes such as bad 02 sensors (all 4) bad dpf sensor, ash in dpf, exhaust recirculation is excessive. It's been a 3 ring circus checking and testing everything and coming up with nothing. All the details are in a different post about the fuel/air/low boost cats? soga. What I need help with is the latest issue this car has come up with. I started the car in order to drive it around the block and into the yard and shutting it down for a couple of minutes. When I went to restart it the engine cracked without starting for several seconds before hitting off and starting. Then after about 5 seconds it dies and won't crank again. The Big Red battery trouble symbol comes on. Also the engine cooling fan comes on running at high speed despite that the engine is barely warm and no ESP see owners manual is on. There are no bars on the temperature gauge like it's dead. I hooked up a charger and left a cable off the battery. Later I tried again but no change. Using my scanner I found a single code "lost communication with ECM". I looked at data stream and it's telling me there is 11.0 volts at ECM. I have 13 back at the battery. I have left the cable off the battery and will try again tomorrow but I bet it's still going to be the same.If I can get this car to start again I will take it to a mechanic that says he can diagnose it.Can anyone shed some light on what I can do here? Can anyone tell me what pins to check on the ECM for 12 volts? I'm not believing anything any more, I want to see the 11 volts. If it's a ground I can find that on my own but otherwise I think maybe the ECM is the clown 🤡 that's been beating me up for a week.Thanks, Bruce

 

I seem to have gotten some where! I have 11 volts at the ECM and nothing is truthful that is being read from the data stream. That means a fuse or more likely a high ground from lose connection , corrosion or chewed wiring. You can't scan for that type of thing. You must dig for it. This also falls in line with the random and miscellaneous codes that have been appearing. The best scanner in the world won't work for you if voltage is off to the sensors and especially the main CPU. There won't be any proceeding forward until I fix this physical issue of voltage .
What would be more helpful from you would be a pin out or schematic.

 

I don't know what a short test is? That's something that came up in your past post.
I have an extremely lower voltage at the ECM then at the battery. 12.85 at the battery and 11.0v at the ECM. That well could be a wiring or connection issue and also a scanner is of little use with corroded or broken wiring. Of course I can't be positive about this but it needs to be investigated. Im not looking for a short, I'm looking for a high Resistance in the power path to the ECM. For this I sure could use a schematic showing connections as well a pin out. I have 45 years experience as an HVAC technician doing services and diagnostics in extremely large chillers that have compressors the size of my car and miles of wires, sensors, solenoids, actuators and a CPU. I have traced out many, many high grounds and chewed wiring that caused the CPU to bring down the whole system. Voltage goes whack and everything goes whack. I am not a car mechanic, I am a car owner that likes to work on his car like most folks on this forum. I don't have the exposure or past experience with this car that others may have but I can figure out what to do. I do have the skills to solve electrical issues when nice people help. So thanks and the VIN is WDBUF22X29B368556. Need an electrical drawing. Bruce
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