CoachWes

So I was sitting at a stop light a few days ago and all of a sudden the car shut off. Tried to restart and it would crank but not start. After waiting on AAA for 3 hours in 100 degree heat, I gave in and called a local tow company, which arrived in 20 mins (sorry that's a rant for another day).


I plugged in my reader when I got home, Bluedriver bluetooth reader, and got a bunch of codes, some of which i knew were a problem for another day and then some that were new. Ill post them because i know someone will ask but there is a deeper issue than i can't find. I've also found that my error code descriptions don't always match up with what the mercedes codes actually are (also something that I'll worry about later because it does normally point me in the right direction).

Bluedriver Code Bluedriver description

P0066 - exhaust camshaft bank 1 short to ground
P0868 - control unit has a malfunction
P0070 - actuator exhaust camshaft cylinder bank 2 has a short circuit to ground
P0278 - Actuator intake camshaft cylinder bank 1 has a short to ground
P0282 - Actuator intake cylinder bank 2 has short to ground
P2182 - mass air flow sensor 1 has malfunction
P1347 - Mas air flow sensor has a short to ground
P0D00 - control pilot charging ventilation switch circuit open
P1B05 - no info
P001B "A" camshaft profile control circuit low bank 1
P0531 - A/C refrigerant Pressure sensor "A" circuit Range/Performance

Then I have a few previously known codes to deal with the adjustable intake flaps (which is on my list to fix soon because the car is going to my son in a couple months)

So, ive done a lot over the last 3 days trying to figure this out so i may leave out some things initially that i have done/checked AND because ive done so much, my brain is starting to hurt (I hate electrical issues sometimes)!

Starting point, found that fuse 43 blows everytime the switch is turned to position 2. If i unplug ECM, fuse doesnt blow, but i think its because power isnt supplied to that circuut. Ill be honest i have tried to find wiring diagram but the more i dig into the problem, the more i find that doesnt make sense even with/without the diagram because if I test just the wire and ground one probe to the frame and then the other probe to one of the wires that plug into the front of the SAM (pictures in the attached document) I'm getting a resistance reading (which shouldn't happen because they are all positive wires)

So to cut to the chase, I found that cylinder 1 coil had shorted, bought a NGK replacement at Napa and installed all new plugs while i was there. I jumping ahead a little but i think the new coil may be an issue too. I did a resistance reading test on each pin of the coil plug and the new coil doesnt match (or close to it) the readings i got on the original coils. Oh BTW, the car has 220,000 miles on it and it has the M272 engine. I didn't write the readings down but I do remember that the resistance was only found on 2 of the pins with the originals and it was found on 3 pins of the new one (I think, I might have that backwards now that I think about it). I may be skipping ahead a little but I know that the coil (passenger side) gets power from the red/blue stripe that come from the plug found in the front SAM unit.

Pictures and resistance readings found in the attachment

Anyway, during the course of troublshootung where this "short to ground" may be coming from here is the end result as of now.

I've disconnected the ECM to troubleshoot the actual problem. I realize that the ECM may also be an issue and also the front SAM (or a relay) possibly.

So the plug I'm referring to is the plug in the front of the SAM which has the following wires (from left to right)

1.Red/blue stripe
2. Red/black stripe
3. Red/green stripe
4. Empty
5. Purple/white stripe
6. Red/white stripe

By tracing the wires, here is where they go:
1 goes to coils on passenger side
2 goes to coils on driver side
3. I forgot because I haven't focused on those
4. Empty
5. Starter
6. Secondary fan

I've mainly worked on 1, 5 and 6. And 5 (purple/white stripe) very little because it's a pain to get to!

So please see the attached document if you haven't opened it yet. It explains more than i can put into words.

Why am I getting a resistance reading on 1, 5, 6 when all of these should be a positive current and not get any reading when testing resistance against the frame. Only a negative wire should, correct?

Also when I test the 2 wires going to the secondary fan when not connected to fan, they test fine along with the males plugs coming out of the fan but as soon as i plug it in, im getting 0.00 resistance (when connected to frame) on both male plugs?

What in the world is going on here and whats making fuse 43 blow?

Side note, ive also looked at cam position sensors and did resistance and voltage tests (found test on Pelican Auto parts site I believe.).

Please help!

Heguli

When you are measuring wire, or a wiring loom for a short to ground, make sure you have both ends disconnected. Like that pin #5, if it's still connected to a starter solenoid, you'll get reading with multimeter.

Couldn't read the attached file, as my phone didn't open it.

Disconnect every componenet that is controlled via ECU, and see does the fuse blow. Quick google search revealed that some had a bad ECU, some had a bad ECU controlled component.

CoachWes

Do you happen to know what all is controlled by the ECU?

Heguli

Not familiar with the M272, but injectors, coils, cam adjusters, intake flaps and throttle body that first came to my mind.