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I made a mistake, I’ve been having plugged dpf problems with…

Ok, I made a mistake...
Ok, I made a mistake, I’ve been having plugged dpf problems with my 2010 Mercedes-Benz ML350, got fed up and pulled the ecm / cdi and sent it away to do the dpf add blue delete with JR performance chiptune.
Problem is I didn’t disconnect the battery first. When I had it on the bench I heard some electrical components cycle on the car and realized I hadn’t disconnected the battery. Yup bad move..
I put it back in and tried to start it. It cranks but won’t start. Well it tries to briefly but no joy.. my snap on scanner says 11A100 component y74 (pressure Control Valve) has open circuit. When I monitor fuel pressure it bounces back and forth from 7-37 psi while trying to start.
Does the ecm cdi need to be re-synced in order to get a run condition again or??
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Answered in 13 hours by:
5/31/2018
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 6,224
Experience: 20 years Master Certified excellent fix rate and have access to factory wiring, and instructions.
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Hello my name is Lou.
I am going over your request now and will reply back soon with some info OR a few questions, Lou

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first thing i want you to do is unplug the engine module again and check all the pins on the module to make sure none are bent.

usually as long as the key is not on then it does not matter if the battery is connected or not when unplugging the module . i am more concerned about the pins since the code we have is open circuit.

Lou

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Customer reply replied 2 months ago
I had a really good look at the pins already, and they were all good. Being that I had just rolled it onto the hoist, and it was in neutral I assume the key was on

ok so next is to unplug the valve and the module and ohm the wires to make sure they are good.

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any luck?

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Customer reply replied 2 months ago
Hi Lou;
So I was waiting to get back to you until I had, looked after a few basic things. I took the mercedes to the dealership to get the CDI paired back with the vehicle after having the performance chip and dpf add blue delete done. They were super helpful. But I still have the Y74 pressure regulator open circuit issue. At mercedes they told me that the valve it self should have between 3 and 5 ohms across poles 1 and 2 it has 3.9. I also checked continuity of the wires from the valve to the cdi (pins 95 and 42) I got tone on my continuity testor, but when I checked resistance over the wires one was 0.1 ohms and the other was 4.3.

4.3 is no good, but tell me which color wire?

sometimes power is shared but i thought on this one it was direct to the module

in that case we cut and run our own wire and recheck

i thnk i fixed one of these before like this it sounds super familiar

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Customer reply replied 2 months ago
They are direct to the module, it was the wire to pin 42 which is the returning signal. I will splice in a temporary wire after work today and see if it will fire up. Ill let you know how it goes.

ok sounds good man

yes 4.3 plus the extra ohms of the valve would throw a code for sure

so the wire overlay would be a great test

let me know!

Lou

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Customer reply replied 2 months ago
Well still won’t start, I’m still having a fuel delivery issue. In the wiring guide that you sent me before. For pin 1-95 which is the one that has high resistance there is a note stating that the regulator gets a pulse and then no more pulses until the motor runs again. I’m wondering if I’m just no longer getting a pulse.
The mechanic at the dealer said I should check pressure from the low pressure pump. I’ve checked the fuse and the relay in the back of the vehicle, both good. What is the best way to check for fuel pressure on the low pressure pump?
Remove the hose from the fuel filter and either tee into the line or dead end it
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ok so then lets check the fuel pump by jumping the fuel pump relay

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we need to jump terminals 87 and 30 of the fuel pump relay

look on the relay you will see the terminal numbers located on the bottom

Lou

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Customer reply replied 1 month ago
Hi Lou; I jumped the relay with a open line at the fuel filter, it pumps fuel to there. I connected the fuel lines again and jumped the relay again and cranked the motor, no start still.... I'm Baffled, if im getting fuel pressure to the high pressure pump, why is it not getting delivered to the engine while cranking, are the injectors not enabled for some reason?
Customer reply replied 1 month ago
I took off the metal line from the high pressure fuel pump, jumped the low pressure pump, cranked the engine and it just dribbled out. Shouldn’t there be lots of fuel there? Or is that a return line? Is there a solenoid valve in the pump that doesn’t allow fuel to flow out of the pump? I figured that being common rail, the rails would always be supplied with fuel pressure, and the injectors would be the only switchable gateway.

y74 and y 94 are wired together for power, we need to verify wiring at the sensors

also as for the high pressure fuel pump

it will just dribble out

high pressure is built off of restriction not quantity

so it will dribble but will fill the lines

we had an issue like this and a injector or 2 were leaking too much so pressure can not be built

but you do not have pressure fault codes yet

you have an issue with the valves that needs taken care of before we can move on

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the red wires with blue stripe should be 12 volts (battery voltage) when the key is on

can you verify?

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as for the temperature sensor code we need to get rid of that as well

i think that one would stop engine operation

let me find the location

can you see the actual value of the sensor in the scanner?

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Customer reply replied 1 month ago
Good morning Lou
This morning I took both connectors off of the cdi box and cleaned them up with abrasive cloth, all of the codes went away except the y74 and y94 open circuits.
I tested the y74 at the connector and pins 1and 2 had 3.14v and 3.5v with the ignition on
Customer reply replied 1 month ago
The y94 ( which correct me if I’m wrong is on the back of the passenger side fuel rail) has 3 wires coming off of it a grey w red stripe, green with red stripe, and red with black stripe

ok lets focus on the red with blue stripe wire only and check it to ground not the other wire

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Customer reply replied 1 month ago
I did check both to ground

ok then we are low on voltage

i am having problems finding the location of the power source

i can see that they are both tied to one another but i cannot find in the wiring diagram where the power originates from

i think its the front fuse box.

that circuit is circuit 87 which comes from the circuit 87 relay

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Customer reply replied 1 month ago
http://knigaproavto.ru/shemy/en/mercedes/m-class/239-mercedes-ml-w164-fuse-box-diagram-20052011.html
Customer reply replied 1 month ago
I found this fuse diagram, it shows a few locations where circuit 87 fuse and relay are based on which engine is in the vehicle. Which one am I looking for?

relay D in engine compartment

front fuse box in front of engine

Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 6,224
Experience: 20 years Master Certified excellent fix rate and have access to factory wiring, and instructions.
Verified
Lou P. master tech and 87 other Mercedes Specialists are ready to help you
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Customer reply replied 1 month ago
I’ve traced it to fuse 104 in the front engine compartment, which is good and showing full voltage at the fuse and through to the wire that leaves the fuse box. Power for circuit 87 comes into the cdi (n3/9 connector 2 position 1) and I get full voltage there at the connector going into the cdi
Customer reply replied 1 month ago
Just tested relay d on the bench it’s good
Customer reply replied 1 month ago
I’ve opened the cdi box and tested the pins on the board. I’m getting 3.5 v do I now assume my cdi is no good? Or is it waiting for a signal to increase voltage on pins 1.95 and 1.42?
Customer reply replied 1 month ago
why are both pins going to y74 positive voltage of 3.5 volts? Shouldn’t one be a ground??
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