Still chasing the slug mode and P0105-128

[JoeHorner]

Still getting loss of boost on our C270CDI when we come to a stop after after a few minutes running.

The only code being thrown for engine or transmission is P0105-128 (Manifold pressure plausibility).

Fuel and air filters are new, can't find any induction leaks, have cleaned the whole intake pipe system the MAP sensor itself, and the EGR valve (which seems to be moving ok with vacuum applied). The vacuum system itself seems to be leak free, although I haven't put a gauge on it yet.

The only other thing I've found is that the MAP reading is around 100 kpa engine off and at idle but, coming to a stop, it sometimes drops to about 960 before recovering. Not sure what their definition of "plausibility" is but pretty sure I'm not stopping in severe tropical depressions!

So, now need to find a way to tap into & monitor the sensor feed and signal wires for a fault that only happens out on the road. Can feel an arduino data logger project coming on....

 

[supernoodle]

You might be lucky and have freeze frame or snapshot data for that P0105-28 fault. Not sure how good MB were at implementing it in 2003.

 

[JoeHorner]

You might be lucky and have freeze frame or snapshot data for that P0105-28 fault. Not sure how good MB were at implementing it in 2003.

I'm not that lucky Whatever it is, it's not setting the MIL and AFAIK they only save a frame when it does on these.

It's frustrating that it only seems to do it when actually driving (can sit idling for ages and be fine). A voltage logger to cover the supply and signal is simple enough to knock together, connecting it so it's reliable while driving may be a little more challenging - especially given the lack of access!

 

[supernoodle]

I've a 2005 e220 and when I use the MB specific diag entry on icarsoft it will not offer any snapshot data for current faults. If I use the OBD mode in icarsoft it will show me a freeze frame for the current fault, MIL or not. This is how it should be. Problem is the PIDs logged in that freeze frame are generic and never have the data you want.

I know that OBD uses diag service $02 for freeze frame and MB specific uses mode $19 for snapshot, but can't believe MB have implemented it for OBD and not $19 that their own tools will use. I think this is icarsoft being a bit flakey.

I like the arduino route, sounds like you're a bit of a geek like me.
I've used these things before (fluke version though) for tapping into wires

1Pair Automotive Repair Wire Piercing Puncture Probe Test Clip with 2mm/4mm Jack | eBay

2PCS Wire Piercing Clip Puncture Probe Automotive with 2mm/4mm Banana Socket. Surface material : PA.

www.ebay.co.uk

 

[JoeHorner]

They look pretty much ideal - got normal needle probes but avoiding shorts is a problem with them.

As for the fault codes, this one is only showing under the MB specific diagnostic - OBD2 shows no faults even when it's set.

 

[Craiglxviii]

Simplest thing to do, spend £60 and get the car looked at by a reputable MB independent garage using Star or Xentry.

 

[JoeHorner]

Simplest thing to do, spend £60 and get the car looked at by a reputable MB independent garage using Star or Xentry.

Cheapest (in fact, only besides the main dealer) I can find around here is a 100 mile round trip and more than double that.

On an £800 car, with repair costs on top (even doing those myself) that's pushing the bounds of worthwhile. Especially seeing as the car is completely drivable as-is.

Besides, there's no challenge involved doing it that way

 

[Craiglxviii]

Cheapest (in fact, only besides the main dealer) I can find around here is a 100 mile round trip and more than double that.

On an £800 car, with repair costs on top (even doing those myself) that's pushing the bounds of worthwhile. Especially seeing as the car is completely drivable as-is.

Besides, there's no challenge involved doing it that way

Whereabouts are you? The reason I say about getting a problem properly diagnosed is, you’ll end up going down one of two routes:

1. Diagnosing it yourself, but taking ages.
2. Fixing it by throwing parts at it.

Nb they’re not mutually exclusive either.

 

[JoeHorner]

Anglesey (far north west Wales). Not exactly known for its industry or anything much except sheep, cows and beaches. None of which are much use in this!

Agreed about the risks of self diagnosing but time isn't a huge issue - the car's fully usable as it is (I've learnt to pretty much avoid the issue by manually changing down to 1st before the car does) and, being self employed, it gives me an excuse to get away from working 24/7 which is always a danger when there's work available.

It's also enjoyably instructive to get your head round exactly how the system interacts with itself and what affects what.

For cost, at the moment only costs are general service items (would be doing filters, oil etc on any car we just got) and tools / toys that will have long term use.anyway. Hence resisting the natural impulse to buy a MAP sensor based on the code until I've worked out exactly what's happening.

By the time I get there I'll also hopefully have a clearer idea of how to approach the inevitable next problem!

 

[ajlsl600]

Go for it I hate parting to fix any of my stuff I wud rather be looking into it for a few weeks and learn something
I have not gone anywhere for hands on mechanical, building. Or much else in 40 yr, advise often. I aim to keep it that way

 

[Doug1234]

It's frustrating that it only seems to do it when actually driving (can sit idling for ages and be fine).
A random thought / guess on my part .. could this be caused by exhaust blockage or partially blocked cat ?
Airflow in and out of engine affected hence the plausibility code thrown up.

 

[JoeHorner]

It's frustrating that it only seems to do it when actually driving (can sit idling for ages and be fine).
A random thought / guess on my part .. could this be caused by exhaust blockage or partially blocked cat ?
Airflow in and out of engine affected hence the plausibility code thrown up.

Possibly, although it doesn't give any other typical symptoms of a blockage. And is pre-DPF, which is nice

 

[ajlsl600]

Pre DPF. V nice

 

[JoeHorner]

Pre DPF. V nice

Yep. One less hassle for the future

 

[alexanderfoti]

Maf plausibility is usually a small boost leak.

Smoke test to identify where, and check all boost hoses by hand.

Just read its a 270 cdi. Get an icarsoft on it. I suspect that is not the right definition

 

[JoeHorner]

That is the (only) code from an icarsoft. Generic OBDII shows a clean bill of health.

Smoke test is on the to-do list as soon as I make up a smoke generator.

 

[alexanderfoti]

That is the (only) code from an icarsoft. Generic OBDII shows a clean bill of health.

Smoke test is on the to-do list as soon as I make up a smoke generator.

Vape pen and straw

 

[JoeHorner]

Vape pen and straw

I like your thinking!

 

[mattkh]

.... I haven't put a gauge on it yet.

Time to put a gauge on it then.

 

[daibevan]

Vape pen and straw

Great tip.