Guys:

I am way out of my depth on this one. Any help or advise is appreciated. Vehicle is a 2001 ML320 (wfiey's car)

Issue: W163.154 No air conditioning - 1) compressor fails to engage 2) aux fans fail to engage.
With my YouCanic Scan Tool I attempted to manually engage the compressor, but the tool failed to establish communications with the module responsilbe for air conditioning functions.
I performed a full system scan, and everything passes with the exception of EAM and EAA having numerous CAN bus faults in each.
Diagnostics:

From the look of things it appears as though I have a CAN bus connection issue that prevents the EAM and AAM modules communicating to the devices they need to communicate with.

History: Earlier this year I replaced the brake master cylinder. That repair required me to raise the fuse panel wiring located immediately behind the fuse block so that I could better access the master cylinder. I may have loosened a connection in the process. Which one, however, remains to be discovered.

I consulted Xentry for the CAN Bus Wiring Diagram for my ML320 (see below)


The EAM is denoted N10/1 and the AAM is denoted N10 in the wiring diagram. It appears to me the EAM is connected to the bus via the AAM. My thoughts are that I must have dislodged a wire leading to the AAM and the -

1. Interior Connector sleeve Z51/3 on the CAN high 2 side (ws wire) or Z51/4 on the CAN low 2 side (gn wire) or
2. Interior Connection sleeve Z51/1 on the CAN high 1 side or Z51/2 on the CAN low 1 side.

Questions: How do I test the CAN Bus connections with my Hand Held Meter? I don't have an oscilliscope. What are the .35 and .5 appearing in the diagram representative of (ohms, amps)? I have read that the EAM is under the passenger side footwell, but the wiring diagram shows it attached to the AAM? Am I right to think they are located next to each other in the engine bay behind the fuse panel? If in fact the EAM is in the passenger footwell, then I am wondering if water incursion could have played a part in this drama via the sunroof drain tube. In any event I will be removing the fender and affixing a proper drain to eliminate any issue relatting to water entering the car in the future.

I appreceitate any help.

Cheers,
.

 

All are "stored", not "current". Clear all, then recheck. Pulling a battery can result in those messages as well as disconnecting CAN BUS connectors from a junction block.
Oscilloscopes are nice, but not mandatory.
A few links to give you some ideas:
https://mbworld.org/forums/e-class-w...is-repair.html
https://mbworld.org/forums/e-class-w...-part-2-a.html
https://mbworld.org/forums/w211-amg/...-no-crank.html
https://mbworld.org/forums/sl-class-...lock-help.html
https://mbworld.org/forums/e-class-w...t-x30-4-a.html

Does your '01 ML320 have an AAC similar to the W210 model? If yes, you can pull the HVAC codes and sensor values directly from the panel.
https://www.mercedesmedic.com/ac-air...le-codes-list/

If you have Xentry you should have "Star Finder". Enter the module identifier for your model and it will bring up a photo of the location. Alternatively, go into WIS for replacing/troubleshooting the module of interest and, again, there will be photos of the location and instructions on removal/replacement.

 

Thanks bbirdwell!

I will check this out and let you know.

 

bbirdwell.

Well I'll be! I cleaned the battery terminals Started the car, cleared the codes and now I can talk to the EAM and AAM.

What is puzzling is when I cleared the codes before cleaning the terminals, the codes came back. After cleaning the terminals and clearing the codes, I am able to access both the AAM and EAM. As well I can get look at the A/C functions. I suppose the reason the compressor is not kicking in is because the coolant pressure is to low in the system. For the ambient temp shown it should be about 40 - 50 psi and it currently shows 21 psi.




Thanks heaps for having me check the battery.