ECU no connection

Hi,

This could be a few things. We need to start at the data link connector to confirm grounds and power supplies.

If you take a look at the pics below, it shows the DLC and where and what to check for. Do this and let me know the results.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

Let me know what you find.

Take care,

Joe

See pic below.

Hi, I have 2 pairs of 12v on the obd plug.

Only 4 wires in there 4-5 neg 7-16 +.

Tried to upload pictures off phone but it doesn't seem to work. thanks for your help.

Hi,

The connections sound good. It did provide 12v, correct?

I attached the entire powertrain management schematic below so you have it as a reference. Today, I need you to focus on the first and second pic below. I highlighted a wire which powers the ECM. I need you to check to see if there is 12v at the ECM.

Also, I'm not familiar with the scan tool you have. Is it able to communicate with other modules?

Let me know.

Take care,

Joe

See pics below.

Hi, I am using star mercedes scanner plugged into big round socket into bonnet ECM unit? Where is the location please?

Hi,

The ECM is under the hood on the right side near the firewall. I had the chance to speak with a friend today that owns a Mercedes repair shop. I remembered your vehicle and discusses it with him.

What he told me was to do what I suggested first. If you look at the schematic above, it shows the power supply to the ECM. He then added that it isn't uncommon for the fuses to get water to them and corrode causing low or no voltage to the ECM.

I checked all through my manual and was unable to locate the fuse location. He felt it would be in the vehicle on the left end of the instrument panel, so check that as well. Wiggle the fuses when testing for power. Basically, position the test light so you can see it. Watch to see if it flickers.

Another common issue he mentioned is the EIS (electronic ignition switch module). Apparently, these are known problems.

Let me know what you find. Also, let me know if this has a push button or key to start it. That can make a difference as well.

Take care,

Joe

If I'm on the correct red, white cable it has no power unclear what fuse it's powered from. Having a look for diagram today on star dia. Thanks

That is where I'm running into trouble as well. If you look at the pic below, that is the wire that supplies power. It shows the power module/fuse box but doesn't identify a fuse or source.

Let me know what you find.

Joe

Hi, I believe there was a bad connection at the ECU cleaned it seems okay now. thanks

Hi,

Thanks for the update. It's appreciated. I'm glad to hear it's running properly.

Let me know if anything changes. Also, please feel free to come back anytime in the future if you have questions.

Take care,

Joe