Limp Home mode

[Trae]

Driving home today, the car went into "limp home mode."
After I finally got home, I pulled these codes:

[FONT=Arial, sans-serif]Pin 6, code 30[/FONT]


[FONT=Arial, sans-serif]CAN data bus to EA/CC/ISC control module (N4/1), interrupted [/FONT]


[FONT=Arial, sans-serif]23 28.0[/FONT]
[FONT=Arial, sans-serif]Read out DTC for N4/1: see DM, Engines, Vol[/FONT]




[FONT=Arial, sans-serif]pin 7, code 2 [/FONT][FONT=Arial, sans-serif] [/FONT]
[FONT=Arial, sans-serif]could be any of these:[/FONT]


[FONT=Arial, sans-serif]EA/CC/ISC control module (N4/1) [/FONT]
[FONT=Arial, sans-serif]Safety contact switch (M16/1s1) 23 5.0, 6.0[/FONT]
[FONT=Arial, sans-serif]Stop lamp switch (S9/1) 24 2.0, 3.0[/FONT]
[FONT=Arial, sans-serif]Safety contact switch (M16/1s1) 23 5.0, 7.0[/FONT]
[FONT=Arial, sans-serif]Criuse control switch (S40) OFF 24 1.0[/FONT]
[FONT=Arial, sans-serif]EA/CC/ISC control module (N4/1) N4/1[/FONT]
[FONT=Arial, sans-serif]Actual value potentiometer (M16/1r2) 23 2.0, 4.0[/FONT]
[FONT=Arial, sans-serif]Starter lock-out/back-up lamp switch (S16/3) (transmission range recognition) 23 12.0[/FONT]
[FONT=Arial, sans-serif]Closed throttle position switch (S29/3) 2 3 11.0[/FONT]
[FONT=Arial, sans-serif]Engine speed (TNA) signal 23 15.0[/FONT]
[FONT=Arial, sans-serif]Vehicle speed signal (VSS) 23 16.0[/FONT]
[FONT=Arial, sans-serif]Safety relay within EA/CC/ISC control module (N4/1) N4/1[/FONT]
[FONT=Arial, sans-serif]EA/CC/ISC control module (N4/1) [/FONT]
[FONT=Arial, sans-serif]Engine harness Check harness wire insulation.[/FONT]




[FONT=Arial, sans-serif]Pin 19, code 6[/FONT]


[FONT=Arial, sans-serif]Idle speed control inoperative Test electronic accelerator, section 6.2.[/FONT]

Erased all codes, then drove another 20 miles at highway speeds. Everything seemed fine. What's up with that?

Will read codes tomorrow morning to see if any came back.

 

[gsxr]

Trae, for the car in question:

1) Has the ETA been rebuilt/replaced?
2) Has the starter lockout / gear indicator switch on the transmission been replaced?

Those are the most likely causes for your symptom + codes.

 

[Trae]

The rebuilt ETA was installed in July of last year.
I JUST had the NSS on the left side of the transmission replaced two days ago because it kept throwing codes. Could the shop have done something on the install to cause these symptoms? I checked the part number to make sure it was correct.

 

[Trae]

I'm hoping it is the NSS and not the ETA. Looking through the receipts, $750 for a new ETA installed.

 

[DW SD]

The rebuilt ETA was installed in July of last year.
I JUST had the NSS on the left side of the transmission replaced two days ago because it kept throwing codes. Could the shop have done something on the install to cause these symptoms? I checked the part number to make sure it was correct.

Trae,
YES, the NSS has an adjustment range when it is installed. I suspect it is simply out of adjustment (hopefully!)
Sounds like since it was just worked on, this is the most likely cause of the problem.
Good luck!
Doug

 

[Trae]

Hi Doug,
After driving last night, there are currently NO codes present this morning. I guess I'll just wait and see if it comes back. (Or, should I try to proactively adjust the NSS?)
Also, when it went into "limp home mode", the ASR light came on with the codes in post #1. This is the 93' 500E.

 

[500AMM]

The rebuilt ETA was installed in July of last year.
I JUST had the NSS on the left side of the transmission replaced two days ago because it kept throwing codes. Could the shop have done something on the install to cause these symptoms? I checked the part number to make sure it was correct.

Hi Trae

I bit off topic, but where did you get the ETA rebuilt?

 

[gsxr]

After driving last night, there are currently NO codes present this morning. I guess I'll just wait and see if it comes back. (Or, should I try to proactively adjust the NSS?)
Also, when it went into "limp home mode", the ASR light came on with the codes in post #1. This is the 93' 500E.

The LHM problem can be very intermittent. You could just keep driving the car and see how often it happens, but it would not hurt to check the NSS adjustment, which should only take about 5 minutes once the car is in the air. It's a simple check, the switch is either adjusted correctly, or not. Click here for instructions, see the note on page 3. Loosen the 2 mounting bolts & rotate as needed to adjust.

Also, was the ETA brand-new, or a rebuild? If it was a rebuild, what company did the rebuild? If it's not on the receipt, look for a sticker on the ETA itself.

 

[Trae]

Hi Arnt,
When I get a chance, I will look to see where it was rebuilt. I think it was a guy in Winston Salem, NC.
Question: When should the throttle start to open the butterfly? Mine does not seem to start until about 45 degrees on the lever arm. Should it be immediate?

 

[gsxr]

When I get a chance, I will look to see where it was rebuilt. I think it was a guy in Winston Salem, NC.

If they just re-wired the ETA, it's possible the internal potentiometers have issues. I believe Jono has mentioned that Beckmann is pretty much the only rebuilder with an excellent record, I believe they test the pots, and also do a full bench-test on the complete unit. I suspect that most other rebuilders just replace the main cable. (??)

Question: When should the throttle start to open the butterfly? Mine does not seem to start until about 45 degrees on the lever arm. Should it be immediate?

With the engine off, and moving the linkage by hand, it will start moving around 45°... this is normal.

 

[DW SD]

is there not a procedure where you turn the key to "on" but without starting and move the pedal and the throttle opens? I think I remember a procedure about checking for WOT.

Doug

 

[gsxr]

is there not a procedure where you turn the key to "on" but without starting and move the pedal and the throttle opens? I think I remember a procedure about checking for WOT.

I think this works, but I've never tried it... a second person is required as the pedal in the car must move, you can't just push the linkage by hand behind the manifold.

 

[DW SD]

I want to use the same procedure to make sure my car actually hits WOT at the throttle plate. Hate to leave power on the table!

Doug

 

[Trae]

After driving several times over 80mi., the car drives fine.
This is the only code left, and it will NOT clear:
Pin 19, code 6
Idle speed control inoperative Test electronic accelerator, section 6.2.

 

[maw1124]

Thanks for this, Gents. I've had this a few times this year, and thought it had to do with either the new exhaust or something with the ASR delete, which this car has always had (as a result of the ASR light being on). I haven't had the guys check codes, but will have them do that and check the NSS when it's in next for service. Of course, I'll report back to this thread.

Cheers,

maw

 

[maw1124]

Thanks for this, Gents. I've had this a few times this year, and thought it had to do with either the new exhaust or something with the ASR delete, which this car has always had (as a result of the ASR light being on). I haven't had the guys check codes, but will have them do that and check the NSS when it's in next for service. Of course, I'll report back to this thread.

Cheers,

maw

Gents,

Sorry for the delay here. UPDATE: my guys noted "NEUTRAL SAFETY SWITCH AND E-BOX FAN FAULT CODES IN MEMORY" when checking the car for the hot start problems. They originally suspected the throttle body. They never got to the bottom of the e-box fan codes. There seems not to be enough information available to tell whether the thing is working properly (coming on at the right time, blowing enough air around, etc.). They were able to take it apart and lubricate some bushings without a marked improvement. They did, however, replace the neutral safety switch. This was back in May. I haven't driven the car since, so I'm not sure whether that fixed the problem. Unless you hear back from me otherwise, assume that was the culprit. If I have the problem again (and ONLY if I have the problem again), I will revert back to this thread.

Cheers,

maw

 

[gsxr]

CAN box fan code is pretty common. Unless it recurs immediately (indicating an actual problem with the blower motor), it's usually a non-issue.

NSS is more likely to cause LHM or other problems.

 

[Trae]

I thought this would not return, but I was wrong.
Driving to work, the throttle gave up, went into limp home mode, and ASR light illuminated.
Pulled into parking lot and read codes, then restarted and drove the car with no problems.
I have yet to check the new NSS position, but I will.

Here are the codes that I pulled and cleared:

Pin 6 - #30 [FONT=Arial, sans-serif]CAN data bus to EA/CC/ISC control module (N4/1), interrupted.[/FONT]


[FONT=Arial, sans-serif]pin 7, code 2 [/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]could be any of these:[/FONT][FONT=Arial, sans-serif]


[/FONT][FONT=Arial, sans-serif]EA/CC/ISC control module (N4/1) [/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Safety contact switch (M16/1s1) 23 5.0, 6.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Stop lamp switch (S9/1) 24 2.0, 3.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Safety contact switch (M16/1s1) 23 5.0, 7.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Criuse control switch (S40) OFF 24 1.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]EA/CC/ISC control module (N4/1) N4/1[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Actual value potentiometer (M16/1r2) 23 2.0, 4.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Starter lock-out/back-up lamp switch (S16/3) (transmission range recognition) 23 12.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Closed throttle position switch (S29/3) 2 3 11.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Engine speed (TNA) signal 23 15.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Vehicle speed signal (VSS) 23 16.0[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Safety relay within EA/CC/ISC control module (N4/1) N4/1[/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]EA/CC/ISC control module (N4/1) [/FONT][FONT=Arial, sans-serif]
[/FONT][FONT=Arial, sans-serif]Engine harness Check harness wire insulation.[/FONT][FONT=Arial, sans-serif] [/FONT]


[FONT=Arial, sans-serif]Pin 8 - #5 Maximum allowable temperature in module box (F23) exceeded 2).[/FONT]


[FONT=Arial, sans-serif]Pin 19 - #4 air injection inoperative.[/FONT]


[FONT=Arial, sans-serif]#6 idle speed control inoperative.[/FONT]

 

[gsxr]

A digital scanner would help narrow down the codes for pin #7... a shot in the dark would be the stop lamp switch (S9/1) but it's hard to say without the exact digital code.

The NSS isn't likely but it wouldn't hurt to double-check.

Who did the ETA rebuild? Pin 19 code 4 is not a common code and usually points towards the ETA...

 

[Roma_500E]

A digital scanner would help narrow down the codes for pin #7... a shot in the dark would be the stop lamp switch (S9/1) but it's hard to say without the exact digital code.

The NSS isn't likely but it wouldn't hurt to double-check.

Who did the ETA rebuild? Pin 19 code 4 is not a common code and usually points towards the ETA...

Regarding NSS.
When I was driving my car and shifted manually from D to 3 and pushed the pedal little bit, from time to time I got ASR on and LHM.

Restarting car helped to go to normal. However, if I try to do it again (D to 3) I got the same result.

So I replaced my NSS and I do not have this issue so far.

Not sure but it seems it has something to do with NSS.

 

[Trae]

Beckmann did the rebuild.
This is a very intermittent problem, at this time, with only three occurrences in the last two years, BUT, I do expect this problem again unless I can get to the bottom of it.

 

[emerydc8]

Sorry to hear this, Trae. Where was your ETA rebuilt? The prior owner of my E420 had the ETA rebuilt at 4Mercedes and the first one was DOA. The second one lasted about three years before it started throwing codes (mostly when it was cold and damp out). I eventually replaced it and the car has been running great.

 

[Trae]

Thanks Jon,
I am going to take the "shot in the dark" and replace the stop lamp switch, since it has coded in the past. Anyone know the part #?
Also, I'll put it on a lift and adjust the NSS per procedure. This problem did not start until I replaced the NSS.
The rebuilt Beckmann is only two years old.

 

[emerydc8]

At $20.40 from parts.com, I guess it can't hurt to replace the stop lamp switch. The part number was 000 545 99 09, but was replaced by 001 545 01 09. It is referred to as a Brake Light Switch/Stop Lamp Switch and is part #53 in the epc under Pedal Assembly.

 

[Trae]

Thanks Jon,
I am not EPC savy.
What are you doing up at this hour of the night in AZ? Are you a night shift worker?

 

[emerydc8]

I fly for an airline, so in the last two weeks I've traveled from TUS-ORD-CVG-ORD-HNL-OKO-OSN-ICN-HKG-BAH-KDH-RIX-JFK-LAX-TUS. I think I am still on the Hong Kong time, which means it's time to hit the hay. I'll eventually get back to a semi-regular schedule about the time I have to leave again.

 

[Trae]

After driving 100 miles without incident, I pulled codes again.
These were the only codes:

Pin 8 - #5 Maximum allowable temperature in module box (F23) exceeded 2).


Pin 19 - #4 air injection inoperative. Will not clear.

 

[gsxr]

Pin 8 - #5 - Usually not a big deal, but I'd check if the blower is functioning.

Pin 19 - #4 - This is of more concern, but you need to clear it and see if it comes back.

Remember that after clearing DM (pin 19) codes, the engine usually needs to be started again before the code will fully clear. It would be very unusual if you had DM code 4 with no other codes from other modules. I'd expect this one along with something from E-GAS or LH.

 

[Trae]

Since I could only clear one code at a time, I bet that code #6 cleared when I started the engine and #4 remained from last time.
As you can see, in post 18, I did have an E-gas code #2.

 

[gerryvz]

Agree, the blower code is not a big deal, I get it all the time.

I also get the air injection code, and have for years. Lights up my CEL about once or twice a year. I just reset it and go on. Never been an issue yet.

Cheers,
Gerry

 

[JordiC]

I have had the pin 19 #4 for about 3 years now. The code re-appears about 2 days after a reset, every time. One day I will replace the air pump but for now I will live with the CEL.

 

[gsxr]

WAIT, sorry, I got mixed up with the codes... DM #4 air injection is not a big deal. Could be the air pump, O2 sensor, or a few other things. If it's intermittent, don't lose sleep over it.

I was thinking you still had DM code #6, idle control inoperative (as mentioned in posts 1, 4 and 18). THAT code makes me suspicious of the ETA.


Bad Dave, no soup for me, etc...

 

[gerryvz]

Bad Dave, no soup for me, etc...

Indeed.....VERY Jelmerian of you ....

 

[Trae]

DM code #6 does pop up every time this happens.
I wonder why I can go for months without going into LHM, then, out of the blue, it happens?

I am definitely going to have to meet Jelmer next time I am in Amsterdam!

 

[T-500]

Hi Gents,

It's been a long time, but I still have my '92 500E
- 136k km now.

I experienced LH Mode for the first time, on Saturday.


High speed accelerate onto highway - pedal floored, from 50 kph.

ASR and CEL lit.

Restart, and it was reset - tried high speed passing 80 kph to 140 - no problem.

Recent work, 2000 km ago, new fan clutch, new cooling sys. sensor(s), new thermostat, new reserv. tank, new coolant.

500km ago,
New distributor caps and rotors,

Saturday,

New battery, after disconnecting amp with internal short.

New correct Bosche non- resistor spark plugs,

Cleared codes for "low voltage" and EGR open/short.

Only EGR came back.

Removed and inspected EGR - diaphragm works, channels clear, no deposits.

Old spark plugs showed proper wear, even and no issues, no deposits.

Car feels more agile after new caps & rotors.

Will try and pull codes tonight.


The only performance issue is that the tranny is needing a rebuild - reverse is delayed, and some up shifts under moderate accel.

Could the tranny be related to LHM ?
Would that be rooted in NSS switch ??

Any thoughts would help, I have a long hot mountainous road trip in 2 weeks.

Thanks

 

[DerFuror]

It's been a long time, but I still have my '92 500E...

I experienced LH Mode for the first time, on Saturday.

Could the tranny be related to LHM ?
Would that be rooted in NSS switch ??

It has been a long time. Good to know you're still kicking.


The only times I had similar LHM experiences with my car was because of a shot NSS (See Part 5 - Post #40 of this thread).

NSS replacement corrected the dreaded occurrences (a definite Safety issue) for me.

 

[gerryvz]

Sean,

I've been WONDERING where you've been at various points over the past year. Great to hear you're still kickin'

Thanks for the post, and don't be a stranger !!

Cheers,
Gerry

 

[T-500]

Thank you, DerFuror

That is encouraging info.

I will see which codes I find, but perhaps I should just replace that switch as a matter of course, if it's not too difficult.



Gerry,

Thanks, it's nice to know that reliable and graciously welcoming 500Eboard is still here, and many of what will be 'lifetime members'.

Great article in a magazine lately, about the 500E, a little anecdote from Dean, and a glowing recommendation of your site.
It was good to see that.

I have been diligently promoting MB's in Western Canada, using many of the suggestions from members on this site.

I was recently elected Pres. of the MBCA BC Section.

It was uncontested... LOL.

Maybe they know something I don't.

It's nice to 'see' everyone, again.

Cheers,

Sean

 

[gerryvz]

I was recently elected Pres. of the MBCA BC Section.

It was uncontested... LOL.

Maybe they know something I don't.

Congrats. I was president of the Houston section for about 16 months, and honestly it's a huge job to be done correctly. I don't envy you, and hopefully you have a good group of volunteers & active members to work with in the section there. My passion was much more geared toward running this forum than running an MBCA section.

Much luck, and like I said, don't be a stranger here !!!

Cheers,
Gerry

 

[T-500]

Thanks, it has its challenges, but I DO have an awesome crew!

Fortunately, many good examples have been set for me.

I also have an appropriate car with Presidential bearing!

I note too that you, me, and Allen Stephens, all possessed these cars during our terms.

It does demand respect.


Meanwhile, I was not able to use the scanner today. Hoping to get it tomorrow. I shall be interested to see if there are codes related to the ETA.

I know an MB mechanic who sometimes lends advice - he is thinking it is likely the ETA, and has no idea what the NSS would do to initiate a LH mode.

Will let you know how far I get - I may just need to observe it on my road trip to Wine Country, in a couple of weeks.

I'm hoping it won't give me grief, publicly - I'm expecting about 20 cars from the Seattle, Victoria, and Vancouver Sections.

 

[Klink]

Aside from the known issue of the disintegrating wiring in the pigtail harness of the throttle actuator, the transmission range indicator switch (an additional component inside the NSS) is the by far most common cause of EA switch off.

The selected transmission range is a monitored variable of the EA for a number of functions. There is a completely separate circuit inside the NSS unit that reports that he selected transmission range to the EA by switching in various fixed resistances (a technique commonly referred to as "voltage coding"). Note that there are two tiny additional terminals at the plug connector for the NSS. The variable resistance is presented directly to the EA across these two terminals. Anything else that may "want" the range selector information gets it from the EA over the data bus.

The circuit board inside the switch assembly can crack and/or develop loose solder joints. The wildly variable resistance caused by this makes the EA switch off. Interestingly enough, the EA fault logic will often code for a defective EA electronic control module! Note that the brake pedal switch is another common cause of these symptoms, and that it also frequently causes The false setting of defective module codes.

 

[maw1124]

Add me to the list of people who (1) had this problem, (2) suggested NSS to my trusty mechanic, (3) who had no idea why the NSS would cause it and searched for other problems, (4) finding none, he replaced the switch at customer's request, and (5) the problem never re-occurred.

I think this is one of those "experience matters" things with these cars, which is why I so appreciate the combined experiences of the folks here. If it was my car, I'd throw a NSS at it as a matter of course, particularly given Klink's explorative answer. Sounds like the internal electronics just give after a while.

Good luck. Cheers,

maw

 

[Klink]

Interestingly enough, the experience came early, as this fault was rampant when these cars were new. They have significantly improved the QC of this switch unit over time, so fewer and fewer people are familiar with it, but starting in late '91, everyone that worked in a dealer service department got familiar with a quickness. LH equipped vehicles had this fault in droves, often several times on the same vehicle when they were still in warranty. It plagues non-ASR vehicles with running faults as well, but since limp throttle isn't one of them it remains massively under diagnosed on those cars...

 

[T-500]

Kline and Maw,

Thank you for your patience to explain to me how you arrived at your conclusions.

From your experiences, it sounds like it would be prudent to replace the NSS regardless of the howls of protest I shall no doubt hear ;-)

I take it that NSS replacement is fairly simple matter?

It sounds like a better alternative to buying somebody else's used ETA for $375 on eBay - thx Dave M., while sending mine away for rebuild, and finding it made no difference.

Hoping to get the scanner today to pull codes.

Thanks,

T-500

 

[Glen]

Interestingly enough, the experience came early, as this fault was rampant when these cars were new. They have significantly improved the QC of this switch unit over time, so fewer and fewer people are familiar with it, but starting in late '91, everyone that worked in a dealer service department got familiar with a quickness. LH equipped vehicles had this fault in droves, often several times on the same vehicle when they were still in warranty. It plagues non-ASR vehicles with running faults as well, but since limp throttle isn't one of them it remains massively under diagnosed on those cars...

Klink, out of curiosity, what symptoms are present on non-ASR cars?

 

[Klink]

Klink, out of curiosity, what symptoms are present on non-ASR cars?

These can exist singly, or in combination, and are usually intermittent: Low on power, incorrect idle speed, idle speed surge, cruise control won't engage and/or cruise switches off by itself, engine stalls especially on overrun, won't rev over about 4K RPM, and no doubt some others. Obviously enough, stored fault codes for the switch, and / or fault codes for a defective cruise control/idle speed control module...

 

[samiam44]

FYI,

Worrying about the fan is not an issue. I believe it was Klink(?) that pointed on that they were deleted in later years(94-95?). So don't fret about the overheat warnings.

I don't know a thing about them new, but can say all my cars in short order had CPS, NSS, and the trans pressure switch give issues. The first and last should give codes. Pressure switch seems like they will leak a bit before throwing a code.

CPS gave me backfiring and weirdness before the code became consistent. Dealer tech session, it was obvious with the diagnostic equipment vs my blink light.


Michael

 

[maw1124]

FYI,

Worrying about the fan is not an issue. I believe it was Klink(?) that pointed on that they were deleted in later years(94-95?). So don't fret about the overheat warnings.

Yeah, one of the red herrings that my guy was all over was the ebox fan codes. I recall it costing me a couple of dollars for him to figure out that it had nothing to do anything. It looks like a case of Mercedes over-engineering, but in SoFL I like to make sure anything having to do with cooling is operating well. I didn't know the fans were subsequently deleted.

On the contrary, I recall the NSS being very simple and inexpensive to replace.

Cheers,

maw