Help Guys, in limp mode my brain is fried

[gsxr]

Jay, also test and see if you bury the throttle from a stop, if you get limp mode as it goes through the gears at WOT. If the issue is repeatable, I'm suspicious of the throttle linkage adjustment, and also double checking the NSS adjustment. Are the shift rod/linkage bushings good at both ends?

Hopefully codes may shed additional light here. If you have a spare E-GAS module, try that also. I would ignore the codes indicating CAN reception problems, these are almost always "ghost codes" that send you off on snipe hunts. Also wouldn't hurt to verify the switch behind the gas pedal (S29/3) is good & adjusted properly. Links below:

https://www.500eboard.com/forums/showthread.php?t=1438

https://www.500eboard.com/forums/showthread.php?t=742

All of the above are long shots, but when you start getting into weird stuff like this...

:dunno:

 

[jaymanek]

The w124 zone pdfs don’t seem to be there anymore. The linkage adjustment seems fairly common sense but want to check I’m not missing anything.

I have access to WIS so will search on there tomorrow.

The nss is reading fine under actual values.

I agree that this thing seems linkage related.

I will see if I can make the fault occur.. although I’m conscious of potentially damaging my new ETA!

 

[Klink]

Everything that Gixxer /\ said, and excuse me if you've already been this route, but the transmission range/neutral safety switch section that reports the trans lever position to the EA were prone to transient intermittent faults, usually due to cracked solder joints. They would frequently cause the code 007/faulty control unit. They tended to do this on sudden hard throttle applications. They usually looked fine on the actual value screen. The CAN codes are very likely only due to the EFP/E-gas/EA control unit shutting off it's outputs upon detecting an internal or external malfunction. Also beware of corrosion damage inside the bottom of the harness plug for the range switch...

 

[gsxr]

Jay, the FSM / workshop manuals are also available on this site... here's the link:
https://www.500eboard.com/Manuals/Servicev3.2/W124/Main.html

I wouldn't worry about damaging the new ETA. They are pretty tough items!

 

[gerryvz]

124-zone is off-line because his hoster bailed on him, but is expected to be back up at an undetermined point in the future when he gets a new hoster.

Please do not widely share the manuals on this site. They are here solely for the benefit of long-time members. If the word gets out, I will change the URL and/or remove them from the site. I've had to do that once in the past.

If you look for the green sub-forum text on the main page of the forums, you'll plainly see the link to the manuals.

 

[jaymanek]

Only real code from yesterday’s limp.

I have been able to make it reoccur. Annoying but fun to floor it at every opportunity!

Officer I’m driving like a lunatic because the 500e board said I had to...

 

[gsxr]

See attached for a few different things to investigate... remember the SDS only shows one of the several possibilities for the E-GAS code.

The DM code is caused by the E-GAS, once you cure the 007 fault and limp mode, the DM 006 code will go away too.

 

[jaymanek]

I have ordered a used E Gas module. Slightly different part number.. ends in 632 rather than 732 but a quick search shows it should be fine.

I will recheck gear linkage to NSS. Im sure its ok though.

 

[195910]

Sorry to hear this Jay, its one of those 1% cases. We hope its sorted this time.

 

[Klink]

Did I miss it earlier? If so, sorry. Have you TRIED a NEW trans switch? Cold solder joints in the switch combined with the vibration of hard acceleration can cause your exact sequence of events you are describing. You don't even have to install it. Just plug it onto the harness and move the control lever of the switch to the position corresponding to "D" then drive it and see. And obviously yes, the TRANS SHIFTER linkage and/or the switch adjustment could do it if either or both are just on a borderline. That code has seldom been caused by the E-gas module itself. If it turns out to be, you can also try replacing any of the larger electrolytic capacitors in the e-gas module. Obviously, if you have access to a cheap or free E-gas and want to try it first, fine. However just about every car that I have had 007 on, and there have been many, was caused by the trans switch. While we're on the subject, almost every 006 has been a brake pedal switch. In just about all cases, the actual values for both looked fine, and you could only see the brief deviations in the signals if you captured them on a scope...

 

[jaymanek]

Thanks... Yes the NSS was replaced by me last week. I checked actual values on Star afterwards, all was ok.

The only thing I noticed was that I didnt like how the black arm on the NSS fits onto the selector lever. No real lock or clip to keep it from sliding backwards. Not likely to happen i know but not very Mercedes either.

I didnt notice any play in the linkages but access is tight so ill check again.

In fact the whole transmission may be coming back out soon anyway as I have an annoying ATF leak... Annoying because the transmission was totally overhauled by someone I trust to do it right. Yet there is a leak and I cant see where it is coming from.

 

[gsxr]

Jay, most trans leaks can be fixed without pulling the trans out of the car... exceptions are the front pump seal and converter seal.

The NSS lever has a black hollow protrusion that fits into a hole in the metal selector shaft lever. These should be tightly clamped and not able to slide anywhere. And, the NSS has to be adjusted with a 4mm wire/pin through the hole, before tightening down the 2 bolts that clamp the switch body to the tranny.

FSM procedure:
http://124performance.com/docs/mb/transmission/trans_722_switch_R+R_1.pdf

 

[jaymanek]

Ahh I didnt do that 4mm locating tab part... ill check this tomorrow. Thanks for that!

Im also wondering if my shift lever may be bent, as I recall it looking a different shape to those pictures. Ill check..
I have a spare transmission from a W126 sitting here so can steal the lever from that one if needed.

If this is the fault, it makes sense. I never had code 7 with original ETA fault. Whilst waiting for the new ETA, I replaced the NSS. I guess if I didn’t set it up correctly it would explain my new code 7.
Although even with the two 10mm bolts loose, there really wasn’t much “adjustment” in the position of the switch..

 

[gerryvz]

Yep, super-critical that the switch be properly aligned with the 4mm drill bit or allen key before cinching it down. If not, things won't work correctly. Even 1 mm out of alignment can affect things.

HOW-TO: https://www.500eboard.com/forums/showthread.php?t=325

 

[jaymanek]

The NSS was not aligned... I have done this and hopefully that was the cause of the issue. Time will tell! Thanks to everyone for the support thus far.

 

[jaymanek]

Hi All, Just to update...Not had limp since I adjusted the NSS. I guess that was the problem.

I did however get ASR warning a few times. A code read brought up brake switch, already new. I fitted another new switch. After fitting I realised I had no brake lights at all!
Later I found they were intermittent.
Then later that day the instrument cluster went dead totally....
I realised this had to be some other voltage issue.
Both brake switch and cluster are fed from same fuse... Guess what, I had used all new aluminium fuses, already corroding! Replaced fuse and no problems since.
New copper fuses on order.

Now the only thing left to iron out is the Trans leak. I really cant understand it. It seems like its weeping from gasket but its not.
It only leaks after a drive. It will leak for a while when coming to astop. Then it stops until the car is driven again.

I thought it was from the breather but its all dry up there.

I can see some fluid around the top of the kickdown cable actuator, but that doesnt make sense?!

Im going to try cleaning the area and covering it in Talcom powder to try and trace the source.
Problem is, its extremely tight up there, very difficult to see anything, even with my snap on borescope camera.

 

[gsxr]

Jay, have all the codes remained exorcised since adjusting the NSS and replacing the brake switch?

 

[Eno]

What is the root cause for no brake lights after you replaced the brake switch behind the pedal.


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