Mercedes-Benz Forum banner

1 - 9 of 9 Posts

·
Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
Joined
·
4,086 Posts
Discussion Starter #1
Hoping to grab the attention of some of you guys who know the 163 inside out.

2004 ML350, been in various shops in the past few months. Complaint was hesitation upon take off and stalling.

So far various shops have...

Fuel filter
MAF (genuine Bosch) 3x
Spark plugs
APP

Below is the job I did:
Brake booster line replaced along with the fitting to manifold, due to crack and vac leak
All vacuum lines replaced, most of them failed smoke test
All breather hoses replaced

Truck runs much better, though occasionally it still exhibits the same symptoms as complaints above. I also want to stress that CEL was NOT on, although all codes were stored and marked as present. CEL was also working, and in monitor readiness MIL trigger was off.

P2004-4 MAF circuit (generic P0104)
P2001 EGR fault (generic P0400)
P2047 misfire on #6 (P0306)
P2039-8 oil sensor signal is implausible (P1999)
P2003 SAI fault (P0410)
P2043 random misfire (P0300)
P203B Fault in fuction monitor in electronic accelerator (P0221)

Customer only cares about the hesitation and stalling, does not care for any other issues. So the EGR, SAI and misfire have to be put to the side. The freeze frame data for most of those were only 1 occurrence over 1000 miles -- in other words the ECU only triggered the code once.

Now, what I'm really interested is the P2004-4 and P2039-8 code -- the MAF circuit code was triggered 16 times and the oil sensor signal was triggered 96 times.

And yes, the oil light is on the cluster, though truck runs fine, oil pressure is at 25 psi at idle and goes to 50+ @ 2500 rpm. Dipstick shows oil and it is on correct level.

I've attached alldata on P0104, on test #2 for 5V voltage supply, if the 5v reference voltage is not correct, it is saying to check for these for a short circuit:
  • B28 (Intake manifold pressure sensor)
  • B37 (Accelerator pedal sensor)
  • B40 (Oil sensor (oil level, temperature and quality))
  • M16/6 (throttle valve actuator)
  • B4/3 (Fuel tank pressure sensor)(only )
Interestingly enough, the oil sensor is on the list. But if I pull up the wiring diagram on either alldata or Mitchell, all sensors listed have their own dedicated wiring to the ECU.

I know this is a common problem on Dodge vehicles, the ECU would output a 5v reference voltage to a whole bunch of sensors on the same wire and if one of the sensors were shorted internally, it would pull down the voltage across all other sensors and make the car act crazy. IIRC the throttle, MAP, MAF and oil pressure switch were on the same 5v reference wire, so the engine would just become unresponsive if any one of the sensors were to short out internally.

My question is thus, does the ME 2.8 ECU share the same 5V reference voltage across the above mentioned sensors, or does it output individual 5V reference voltage, so if one sensor goes kaput, it doesn't pull down the rest? I'm guessing it's the same 5V reference voltage across multiple sensors, but would like to verify.

On monday I will be checking out the oil sensor harness and the MAF harness as per the P0104 guide.
 

Attachments

·
Registered
2003 ml500, 2004 ml350
Joined
·
1,777 Posts
The stalling almost sounds like a bad crank shaft position sensor.

The hesitation does not.

But after installing the MAF was the throttle position relearned?
 

·
Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
Joined
·
4,086 Posts
Discussion Starter #3
Yes, but it doesn't stall at stop like you'd think.... it stalls when going over bumps. And to make matters worse, when you go over a particularly bad road section, it will do either:

1. Stall
2. Throttle goes dead -- transmission goes into neutral, engine goes to idle and no amount of throttle does anything. A restart fixes it.
3. Do nothing.

Most of the time, it's nothing. Truck acts as expected. Sometimes, it will stall. Which is very very bad on the freeway. Sometimes, throttle goes dead. Which is also very bad on the freeway. Sometimes it will actually pull a bad CPS and stall at stop.

I took the truck from the customer and basically have been commuting to work and back for the past few days in order to understand the exact symptoms. So far, I have been able to replicate every single complaints.

Yes, a new CPS is in order, and is in fact on the way.

And yes, after replacement MAF the throttle relearn was done. Multiple times to no avail.

The hesitation at take off and while rolling feels a lot like a frayed or stretched throttle cable.....nope, brand new. I tensioned the new cable so it has the proper amount of slack, but the slightest touch of the pedal moves the APP and I am able to verify that in SDS. But you push the throttle, nothing happens. Push it some more, nothing happens. Push a little bit more, then it picks up and accelerates.

Hence why I wind back to the possibility that the defective oil sensor somehow contaminating the 5v reference and fucking it up for all other sensors that also use 5v as a reference signal....which conveniently, include MAF (have codes), APP (have codes), throttle body (no codes....yet) , MAP (did have codes, vacuum hose broken, no codes since vac leak repair), fuel tank sensor (no codes...yet).

Oh, forgot to mention....unplugging the MAF and driving it to see how it runs -- it runs worse! Hesitation is worse, it will stall a lot more often.
 

·
Registered
Dallas, Texas
Joined
·
7,971 Posts
MAP and oil level sensor share same 5V reference at Z7/41.

Any previous repairs like water pump or alternator? I have seen harness portion going to level sensor routed in front of water pump instead of behind or smashed against the block during alternator replacement.

Code P203B looks interesting.
 

Attachments

·
Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
Joined
·
4,086 Posts
Discussion Starter #5
Now that's interesting to know, the car runs really badly with MAF unplugged when it should be able to run perfectly in failsafe default mode.

No recent work that I'm aware of, but I will check anyway. Oil sensor replacement looks to be fairly easy, if messy. Will check for pinched wires, or insulation rubbed raw.

Yup, P203B is interesting. Never seen that before, automatic ECU replacement if the code keeps popping up.... Usually there's a whole bunch of testing before recommending replacement. Doubt that's necessary, but I've been proven wrong before.
 

·
Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
Joined
·
4,086 Posts
Discussion Starter #6
Update:

Unplugging the oil level sensor = massive improvement. No more hesitation, the 5v rail on both MAF and MAP were now rock solid at 4.8-5v @ ignition II.

P0104 (MAF code) did not come back. EGR code did not come back.

P203B did come back, however. Went downhill, stopped, and when tried to accelerate, no throttle response. Had to restart to move, P203B stored. Guessing ECU replacement is imminent. Will need cust. authorization.

Doing oil level sensor and CPS tomorrow....oil level sensor was definitely the culprit for the hesitation issue.
 

·
Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
Joined
·
4,086 Posts
Discussion Starter #8
I suspect that normally the oil level sensor fails to report level sensor and that would be that.

However, on this car, I believe the failure is such that both the 5v, gnd and the signal lines were corroded, or crossed or something, because as I would hit a decent bump, the wires would short together and pull down the 5v rail for everything...including MAP/MAF.

Given that the wiring diagram shows the MAP sensor sharing the same 5v rail as the oil sensor, and the diag tree for MAF says check for any circuit issues on the oil level sensor, that would explain it.

With oil level sensor unplugged, the truck runs nice now. Even when I unplug the MAF, it runs well enough in failsafe mode, no longer hesitating, etc.

Certainly the first time I've seen it on a MB, but not in other vehicles. Dodge cars/trucks were notorious for that, bad oil switch pulls down the throttle and MAF.
 

·
W163 and General Mercedes Host
Joined
·
3,270 Posts
Learn something new here, everyday.
Great info.
ugh! This requires raising the engine, lower the oil pan to access the OLS. 6" more or less.
And then there is the special/correct way of applying the seal compound on the upper and lower part of the pan.
I've read about owner's disconnecting the oil sensor at the cluster - couldnt be bothered, I guess, to fix the sensor issue.

Cheers.
 
1 - 9 of 9 Posts
Top