Gents,

I was messing around with someone's M157 and I got this :



I do not know if M278 can do this Compression Test. Relative compression test.


Thanks

 

What version XENTRY are you using? Interesting that it says "is no longer available". Maybe check with @BenzNinja .

 

No issues here.
M278 definitely works on my version as I used it fairly recently on my friends/client W222
Honestly, when we talk about XENTRY here, we REALLY should list versions we’re using and Multiplexer.
Just like the computer industry, software versions and interface are important and seem to be missing functionality depending on which flavor you’re using.
Curious, @S-Prihadi, do you have access to LIN-BUS diagnostics?
It could be user error but, seems not everyone has access to this either.


(I’ll see if I can access M157 compression testing in simulation mode)

Good Luck

 

Hmmm, he has BenzNinja so should be the latest version.

 

When it comes to software, newer revisions do not always equal more features. Sometimes they take things away from older versions for compatibility with newer products or the software itself. Not saying that’s what’s happening here, but there is definitely some functionality differences depending on which flavor of XENTRY (and maybe multiplexer) you’re running. Passthru is a good example too.

I think JR is using the same version as @S-Prihadi and JR couldn’t access LIN-BUS testing. (it’s kinda buried, so maybe it wasn’t easy to find). But so far, that seems to be one test that some can access, and others don’t appear to have access to that testing page in the application.

To be honest XENTRY is pretty Kludgy as far as software goes, but it’s all we got and as good as it gets for MB diagnostics

 

I see that all makes sense, I do see the trend of features being removed in newer revisions of software across the industry not just cars, phones alike.

 

Exactly.
This is just the reality of writing software in general. It’s always a compromise. There’s no reason to believe this wouldn’t happen in XENTRY.

 

I wonder if there is a reason behind it. If only we can find out.

 

Compression tests for pre 2012 Amg’s are available for earlier models in Star das. Even my 13 with older xentry software does not offer this feature. MANY features were removed with Xentry and now require vediamo. You used to be able to code whatever you wanted in developer mode in Star.
Coding of parts was done in the guise of theft protection, but really we know it was to drive people to the mb service centers. A crock of bs if you ask me because criminals just break the rules anyway.
Also, the compression test is not really a compression test per se, but it measures the speed of each individual cylinder and compares them to see if there is a difference which would require secondary inspection with a real compression tester anyways. Better to get in there and check the bores and change the spark plugs if you need. It’s pretty quick to get the plugs out.

 

Exactly, if I had a car with real issues, I’d do a leak down (physical compression check minimum) + borescope.
The XENTRY compression test makes for a nice screen shot (for the customer) though

 

To add, as CRC mentioned, yes it works on a m278 and all non AMG vins. I would have the question about whether this was available for an "AMG Lite" such as an A45 or 43. I would this it would work with a 450 but did they turn it off for the 45. Id have to see what year my software if to see if this is something I could check.

 

I needed the xentry compression test to test battery actually, not for true compression test.
The highest battery load on our car is the starter.
I could have used my carbon pile battery tester, but I wanted to first do Xentry compression test so that I can crank engine for 6 seconds without starting it and get a good
scope reading on the amps and voltage drop without pressure from compressing & ignition from fuel .
I don't like removing injectors connectors ( all 8 ) and COP connectors ( all 8 ) and get DTC, simply from trying to simulate crank-no-start.
MB cars does not have clear flood mode of US cars for crank-no-start test.

Side note : CRC asked : Curious, @S-Prihadi, do you have access to LIN-BUS diagnostics?
I don't know, I have never done this test, later today I will check if my E400 has this test or not.
Which module I am to find this test at ? I supposed front or rear SAM...yes ?

I was trying to have a database of amperage needed for crank-to-start of M278/M157 or 8 cylinders engine vs M276.8 or 6 cylinders.

If M276.8 , Xentry compression test crank-no-start the average current draw is 200-220 amps after the 0.25 seconds starter first run all the way to 6 seconds.
M276.8, If crank to start, depending on engine oil temperature , it is 340ish amps at 0.25 second after starter first engaged, and by 0.8 seconds engine already come to life.

This M157 is higher, up to 500 amps at 0.25 second after starter first engaged, and by 0.75 seconds engine already come to life.
This depends on the battery CCA too though, lesser quality battery with higher voltage drop will need a bit higher amps.

My indie knows I like messing around on MB cars if it is HVAC or electrical based concerns, so he let me have a go.
The client does not know about cars much, so his staff at the office is the one who bought a new battery in Oct 2024 of 80A 795CCA.
Naturally bean counters at the office does not understand what is AGM battery vs standard battery , all they know 80A is 80A...so they thought.

Ordinary lead acid battery and non AGM of non reputable brand, does not have the honest CCA like a good Varta AGM Silver Dynamic.
If using MBapproved Midtronics battery tester, Varta AGM 80A CCA 800 EN is actually 950 CCA EN when virgin new.
Varta AGM silver dynamic is the only brand and type I can source in Indonesia as a good brand and type for my car.
Original MB battery for Indonesian market is Varta AGM, but black casing, not silver casing.

So owner wanted to confirm if his 1 year old battery is the issue of the engine has issue ?
Good battery is always heavy and not small, if 80A apple to apple.
See below how skinny the 80A of the dumb-azz brand called Brighton non AGM.


Above and below oldie 2017 Silver Dynamic AGM from Varta is the type and size I been using.

Note the word RETIRED and not BAD-DEFECTIVE. I retire my battery once its Reserve Capacity Minutes drop by 25% to 30%. It still crank well but it can't have key in ignition and you listen to music
at low volume for 3+ hours anymore, which is approx 11 amps hour constant. 80A typical Reserve Minutes is 140 minutes at 25amps drain to 10.5 volts, its a standard test.

---------------

Back to M157.
This is grey area if one does not have oscilloscope to test the battery, DMM or regular current clamp is too slow and inrush capable current clamp only read the inrush current and
locked it there, not knowing the full 0.75 seconds to 1 second of story line of the current and voltage drop of crank-to-start---> engine running.

For the curious ones :

This is the crank to start of the M157.981 engine, when it first arrived in my home. Yes, my indie sent the car to my house, he is a nice guy.

Engine is WARM, not COLD. Ambient temp 30C. Crank to start hesitation is obvious.
1 is the peak amperage after starter has spinned for 0.3 second, at 599 amps.
2 is the battery voltage at battery posts directly, dropped to 9.17 volt at the 599 amps.
3 is the time is milliseconds 302.7 or 0.3 second, between start of crank ( locked rotor current) to next highest current peak.


Above shows a battery not suitable for M157 crank-to-start needs.

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Start of crank is equal to Locked Rotor Current, this is what is called INRUSH current when a current clamp has this feature.
My Pico current clamp is 600 amps only, thus you see it flatline to max 600 amps. Scope based current clamp sees everything from INRUSH and all other data captured.
My Flukes regular current clamp can do INRUSH up to 2,000 amps, but I did not use it because I was not after the INRUSH only.
On my M276.8 engine, the INRUSH is worth 677 amps if at COLD 30C ambient /oil temperature based on Fluke current clamp at sampling rate I believe no faster than 20x per second.
Pico scope sampling rate is in excess of millions reading per 1 second, thus we see better with pico scope.

===========================

I then charged this dumb-azz battery first, before I will do another test.
2nd time crank-to-start after battery fully charged. No initial hesitation of stater spin-engagement at Locked Rotor Current, all good.





Data 1 and 2 remain the same as previous, data 3 ( green channel ) is my measurement of voltage drop between battery post to W10 main ground on suspension strut,
and the WTF un-documented ground wire to engine bell housing and thus engine metal block. 0.5 volt is using scope is decent, not great.

So data 1 amperage now reduced to 423 amps only and voltage drop at battery post (data 2) has improve to 9.98volt.


===========

I then test again up to 6th crank-to-start and added FOB key-in-slot at 1 turn clockwise to drain battery at 11 amps for 10 minutes. So I drained the battery less than 3 amps, that 10 minutes worth.
Below is 5th crank-to-start after battery fully charged and drained at approx 3 amps worth.




Here I can start to hear slight hesitation of starter while it depart from Locked Rotor Current or zero speed of starter to 0.25secs spin.


========================


I then use my own E400 battery to test this M157. Mine is year manufactured Dec 2020, start of use June 2021 till today, its is a 4 years old battery .
It is Varta AGM Silver dynamic of 80A and 800 CCA EN, 850 CCA SAE.
3rd crank-to-start on my Varta 80A.



Albeit mine is a 4 years old battery, it is still good and being AGM, its cranking CCA is good.
See data 2,voltage drop at battery post is still at 10.07 volts, did not collapse below 10 volts.


====================


I then tested on my car M276.8, my own battery for crank-to-start. I usually do only Xentry compression test and not crank-to-start.

Cold engine at 30C, crank to start 1st time, let it idle for 30 seconds and I do 2nd time crank-to-start

2nd time crank-to-start M276.820




4th time crank-to-start M276.820




My ground is already a beefed up ground, also M276.8 is only a 6 cylinder engine.
Since voltage drop is dependent on current draw, here you see better values on my engine using the same oldie YOM 2020 Varta AGM silver dynamic 80A, compared to M157.981.
Surprising to see EPC, that CLS63 with M157 engine is spec also for 80A battery 800CCA like M276.820. I thought it would be a bit bigger than that.
P/N is different, but battery is battery if 80A , its CCA is very similar if both are Varta AGM.



M276.8 engine battery above, below is for M157.9








M276.820 mine if Xentry Compression test aka crank-no-start and without fuel injected into combustion chamber and no ignition COP involved.
So it is rather lightweight duty for the starter after 0.25 seconds and all the way to 6 seconds.





Compression Test using Xentry is also a simple way of priming our oil pump after oil change or long time dormant engine, say 3 weeks no engine start.
You can read here how BMW wants their tech to prime the engine oil using starter too : https://mbworld.org/forums/e-class-w...l-priming.html


-------------

Here I am dealing with a non-reputable battery of 80A, which is aging fast.
CLS63 alternator is designed for AGM battery and the float and bulk charging voltage is a tiny bit higher than non AGM. Non AGM battery can age faster when charged at AGM spec.
This battery reserve minutes has dropped to I believed by easy 30%.
The worst part is its CCA goes down fast during the test and the next day when my Indie staff picked up the car.
At night I charged battery full using Noco Genious 5.0 and 12 hours later my Indie staff collected the car, the crank-to-start was so obvious slow at the locked rotor current to the nex 0.25 second.
Sure engine started fine, but when your ear is well trained, it is so obvious by sound that the battery is under performing.

So I told my indie, clean W10 ground at suspension strut tower and clean the WTF under the body ground wire. I did not access the WTF ground wire because my car is using currently the Quick Jack.
By cleaning the W10 and WTF ground wire, I expect 0.1 volt improvement will happen.
I adviced my Indie to tell owner that engine is not a problem and wait till the dumb-azz battery finally weakened enough and fail to start or replace it with the Varta 80A AGM asap, up to the customer.
Its very difficult to explain electrical stuff of this borderline nature to non electrical aware customer.
99.999% of car owner do not own 25 amps load bank and carbon pile battery tester. At the most they rely and believed in electronic battery tester, which I found not the best tool to beat
25 amps load bank and 500-1,000 amps carbon pile battery tester in terms of 100% confirmation what is the actual health of the battery.

======

Jetta,
The Xentry version is the latest one from BenzNinja, I mean latest as in this year after July 2025.
It is supposedly different from the Xentry I got back in 2023 March. I was told it can do newer MB cars.
The SW number I don't care, me IT dummy .
My C4 multiplexer still the oldie one I got from 2023.

Maybe you guys and CRC are correct, newer version of Xentry maybe different than the oldie one I have. Perhaps more restrictions.
But me must find M157 again to do the test to confirm this.

 

Get a resistance tester, Carbon pile tester is pretty old school
LIN-BUS access:
https://automotivetechinfo.com/2019/...-that-battery/

Below pic is the factory version, but there are some better ones available.


Good Luck

 

Same as Jettared I only have SIMULATION menu and not LIN BUS, based on W212 E400, I dont own other models.

But tracking battery and charging status is available, which that is LIN based.


I dont have this :



Mine is like Jetta's


.




I have all what you have for battery consumption pages, it is in REAR SAM module, under sub menu On-Board Electrical System Data. Bear in mind I am on W212.065 and not R231

.


.





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BTW : The low milliamps resolution is too course for me this data. It is showing near 40 milliamps deep sleep mode, actually it is only 5 milliamps.




There are more pages.


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On the subject of very course milliamps resolution shown on the Xentry showing 40mA vs actual 5mA , 35milliamps difference can make me suspect one or two modules NOT sleeping.

This is the supposedly deep sleeping mode currreny draw of CLS63 at 8 milliamps, but it sometimes does some checking and up a bit at 70 ish milliamps.


.



.




However, these reading above is not taken 6 hours after engine kill, less than that.

.

True deep sleep on my car W212.065 needs 6 hours if car been having engine running on the road.
If it has been parked engine off more than 6 hours, deep sleep happens within like 15 minutes after every opening/closing of the doors and K2 relay at F32 shutdown.
Below is an example car been parked for days and I open/close the door.



.

The typical spike during sleep is up to 11 milliamps and 5.6 milliamps as base line. Below is extra 15 minutes logging after deep sleep of 5.6 milliamps achieved.




.

 

I don't trust electronic tester a 100%, even reccomended Midtronics one. I have a few non Midtronics and I don't like them.
I rather do real load test, because the battery chemistry reacts more accurately to real load test.
Real load test can not go wrong, because it is so slow and so time consuming...LOL.

.

 

Yeah, I remember when those Midronics units first rolled out, everyone in the shop was skeptical (me included) and no one wanted to give up our trusty SUN VAT-28 tester.
Though the resistance tester can be finicky, over time we found them to be 95% or better as accurate. And a lot safer, so yes, a few fell thru.

haha I guess you can’t call yourself a journeyman unless you’ve had at least one battery blow up
I had a battery go on a BMW e32, it was inside the car under the rear seat (with seat bottom removed) when it exploded. That was an ugly job…

 

That would be right, as the rear SAM handles charging in your model (and others). At least we know you (and the software version) have access to it.
I thought there was a way of changing resolution, I’ll double check when I get back in my shop, probably Monday.
I’m going to assume you know this, but post this for others who may read this later just in case.
The FOB(s) has to be out of range for the car not to “wake”.

Good Luck!

 

Yes, I would think most will know FOB key need to be away from the car....I hope

I only do my own car batteries and good friends and my yacht* clients ( * 8 to 12 of 200Ah batteries in one go )
So the risk of me getting awful bad batteries which can explode is low, unlike garage dealing with them daily perhaps.

My battery supplier has the Midtronics. I know it is a market leader for electronic battery testing.
In fact W212 rear 12Ah start stop battery has similar milliohms battery monitoring by rear SAM... I don't know if the test signal injection uses special frequency pattern like Midtronics or not.