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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3733
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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I have a 2002 mercedes C320 , car does not connect to obd2.

Customer Question

I have a 2002 mercedes C320 , car does not connect to obd2. Dash displays "3 FAULT". Ignition turns but car is not cranking. 160k miles. New key was bought from dealer still nothing.
Submitted: 8 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 8 months ago.
Hello , what kind of scanner are you using? does the dash and the rest of the car work just does not crank?
Customer: replied 8 months ago.
CreaderVI obd2 scanner, radio is working and windows, dash lights come on and, fault for coolant level, srs (attached pictures). Driver side fuse panel included in pictures.
Expert:  Lou P. master tech replied 8 months ago.
ok, so you may have a issue with your ecm, the issue is your scanner can only read the ecm module so we dont know what other fault codes are in the system, the coolant low message will come on if there is low coolant or a issue with the cooling fan, when did this issue start? after a rain? or out of nowhere?
Customer: replied 8 months ago.
I bought the car like that, guy said out of no where it loss power and shut off and wouldn't start after that.
Customer: replied 8 months ago.
Will i be able to get another ecm from a same car and test it that way to see of it's really ecm? Will i be able to scan the car then? And will i need to reprogram the ecm at the dealer?
Expert:  Lou P. master tech replied 8 months ago.
the only thing you can do with a used ecm is plug it in and see if communication comes back. you cannot start and run it, a new ecm uncoded is the only way also it must be coded at a dealer. BUT that is if this is the issue. do you know how to check power and ground:?
Customer: replied 8 months ago.
Yes i do.
Expert:  Lou P. master tech replied 8 months ago.
ok let me see what we can do without a scanner give me some time.
Customer: replied 8 months ago.
Thanks
Expert:  Lou P. master tech replied 8 months ago.
no problem
Customer: replied 8 months ago.
Did you ever figure it out?
Expert:  Lou P. master tech replied 8 months ago.
sorry things got away from me, i will check a diagram now and let you know what to test, you will nee to unplug the ecm in the drivers side fuse box and test for power and ground, also check a few fuses
Expert:  Lou P. master tech replied 8 months ago.
check fuse 53,54,57 in the left front fuse box with the ignition on, see if they have power and if any are blown. let me know.
Customer: replied 8 months ago.
I should be home soon I'll check them asap. Is that the only thing to check?
Expert:  Lou P. master tech replied 8 months ago.
thats the best place to start, then check to make sure the grounds are present at the ecm, ill get the connector pin numbers
Expert:  Lou P. master tech replied 8 months ago.
CONNECTOR 5 IS THE ONE WE WANT , the engine computer will look just like this on the top. its in the same box as the fuse box.
Expert:  Lou P. master tech replied 8 months ago.
power pins will be 39ground pins will be 5678verify all. then on connector 4 verify pins 1 and 11 have some voltage they should read about 2.5 volts give or take.
Customer: replied 8 months ago.
Thank you for the details I will notify you as soon as I'm done testing.
Expert:  Lou P. master tech replied 8 months ago.
If all match up and we still cannot communicate with the ecm that will lead us to think the engine module has failed.
Expert:  Lou P. master tech replied 8 months ago.
also you want to verify continuity between pin 7 of the obd connector under the dash and pin 29 of connector 4 to make sure it is ok, if it is that will tell me also the ecm is bad. one thing that is important is to also verify the obs connector has power at pin 16 http://www.mediafire.com/view/d0w57ts2z1ad46z/obd2%20pinout.jpg
Expert:  Lou P. master tech replied 8 months ago.
Please take a second and click the stars at the top of the screen to rate me so i may receive my credit , 5 stars is ideal , please request me in the future.Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.
Customer: replied 8 months ago.
"you will nee to unplug the ecm in the drivers side fuse box and test for power.. “ how do i do that with no power to ecm will be present after i unplug it?
Expert:  Lou P. master tech replied 8 months ago.
OK, you will unplug the power and you will test for power on the plug of the wiring harness, silly :) obviously if you unplug the module it will have no power ON THE MODULE , but the connector should have power . understand? let me know i have no problem walking you through it.
Customer: replied 7 months ago.
fuse
53 - 11.88 v
54- 11.88v
57- 11.88vConnector 5
+
3 - 11.87v
9 - 11.88v5 - Grounded
6 - Grounded
7 -Grounded
8 -GroundedConnector 4
1- 2.583v
11- 2.407v29- continuity to pin 7 (OBD) confirmed.OBD
16- 11.9v
Customer: replied 7 months ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Lou P. master tech replied 7 months ago.
hello i have seen your reply i have just not had time to open the diagram and go over all of your readings so do not think i left you :)i will need some time.
Customer: replied 7 months ago.
no problem..THANK YOU!!!!
Expert:  Lou P. master tech replied 7 months ago.
APPRECIATE IT
Customer: replied 6 months ago.
Were you able to figure it out?
Expert:  Lou P. master tech replied 6 months ago.
oh sorry my reply did not post,ok so you confirmed all power and ground and communication lines, that tells me the ecm is fried. all looks ok from my end, you answered all of my questions about the pins i provided. the next step would be to find another car that is the same and swap ecm, the car will not crank or start but the scanner should be able to read the module then, hope this helps, also if you get a new ecm try mercedes ecu out of michigan they are a good company. hope this helps. Please take a second and click the stars at the top of the screen to rate me so i may receive my credit , 5 stars is ideal , please request me in the future.Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.