Neutral Safety Switch NLA?

[The Ry Guy]

Finally got some time to work on my 93 400E that is stuck in limp mode. I sent the ETA out to Beckman Technologies for testing, and they told me they ran it on their test bench for two days and found no fault. So that's good news, but it still starts in limp mode, even after clearing all the codes and disconnecting the battery. The ETA clicks for about a second when the key is first turned to run, but no hum or whine is heard from it like it should be.

The code that comes back on Pin #7 is 2, and on Pin #6 I get 30 (which, I understand is because of going into limp mode).

So going through process of elimination on code 2, I'm ruling out the ETA, and the Idle switch in the accelerator pedal (replaced with new OEM part recently).

So that leaves the E-Gas module, the NSS, and the wiring that connect them as possible culprits.

Looking on line at all the usual parts places, shows the switch NLA or backordered. Does anyone know where I can get one?

Kinda frustrating that the switch was replaced when I had the transmission rebuilt a few years ago.

Perhaps the switch isn't bad, does anyone know what resistance values to check? I assume it's on the two smaller pins on the switch. That send values to the ECU.

 

[gsxr]

The NSS is NLA. There's a forum thread with details on how to repair & test it, and I believe resistance values are in that post. Remember the NSS must be adjusted correctly or even a new one will cause problems. If your NSS was new from a few years ago it's very unlikely to have failed already.

The best method to test the NSS is to view live data from the E-GAS module while moving the shifter into each position. However, there will typically be a fault code specific to the NSS (S16/3). But, you need SDS or other digital scanner that will show you the 3-digit code. This would also help narrow down your analog blink code #2, which is not very helpful - you need the 3-digit code (screen shot below). You could have a problem with S9/1 or S29/3, for example. The ETA and NSS are not the only items which can cause limp mode.

Any chance you have another E-GAS module to test with (from any chassis with M119 engine)?

Was limp mode intermittent for a while but is now persistent, or did this problem occur out of the blue?

Is it "full limp mode" where the first half of pedal travel does nothing, or do you just have ABS+ASR fault lights on with normal throttle control?

 

[The Ry Guy]

Ok, I'll look for that thread and see if I can locate the resistance values for the NSS.

I forgot to mention that I removed and checked the S9/1 Switch last night as well, and it is working properly. No resistance when activated, full open circuit when off. Is S29/3 the one in the accelerator pedal? If so, it is new, and I did check it just to be sure. I forget the resistance value off the top of my head, but it is correct. 1k ohm I think? If it's not, it it located in the ETA?

I do not have another E-GAS module handy. If I'm reading correctly, any E-GAS from a M119 car will work? I'll have to locate one on eBay.

Limp mode was intermittent for a while, but I could sometimes clear it if I shut the car off and turned it back on. Now it's on all the time, in full limp, no throttle for half the pedal travel mode.

 

[gerryvz]

The neutral safety switch has been NLA for several years now.

Neutral Safety Switch replacement (NSS) Failure? or something else. | Transmission and Driveline

I replaced the NSS switch. Still not starting. I replaced the switch because I was having the same issues as everyone else. Not starting in park or neutral, move it around a bit and it will start. Finally one day nothing worked! So I jumped the two wires under the driver's side dash and it...

www.500eboard.co

 

[gsxr]

I forgot to mention that I removed and checked the S9/1 Switch last night as well, and it is working properly. No resistance when activated, full open circuit when off.

S9/1 also requires adjustment, make sure to follow the installation procedure, but this shouldn't cause full limp mode all the time IIRC.

Is S29/3 the one in the accelerator pedal? If so, it is new, and I did check it just to be sure. I forget the resistance value off the top of my head, but it is correct. 1k ohm I think? If it's not, it it located in the ETA?

S29/3 is indeed at the accelerator pedal. All the switches marked M16/xxx are located inside the ETA.

I do not have another E-GAS module handy. If I'm reading correctly, any E-GAS from a M119 car will work? I'll have to locate one on eBay.

For basic testing, yes, any E-GAS from a car with an M119 engine will work. However, if the donor is from a 140 chassis, cruise control will not operate. Ideally you'd source one from another 400E but the 140 modules are more plentiful and cheaper.

Limp mode was intermittent for a while, but I could sometimes clear it if I shut the car off and turned it back on. Now it's on all the time, in full limp, no throttle for half the pedal travel mode.

Hmmm. Also make sure the throttle cable is adjusted correctly, the ETA lever must rest against the idle stop with a small amount of slack at the end of the cable. If the cable is too tight and pulling on the ETA at idle, that will cause Insta-Limp.

 

[emerydc8]

Ok, I'll look for that thread and see if I can locate the resistance values for the NSS.

I forgot to mention that I removed and checked the S9/1 Switch last night as well, and it is working properly. No resistance when activated, full open circuit when off. Is S29/3 the one in the accelerator pedal? If so, it is new, and I did check it just to be sure. I forget the resistance value off the top of my head, but it is correct. 1k ohm I think? If it's not, it it located in the ETA?

I do not have another E-GAS module handy. If I'm reading correctly, any E-GAS from a M119 car will work? I'll have to locate one on eBay.

Limp mode was intermittent for a while, but I could sometimes clear it if I shut the car off and turned it back on. Now it's on all the time, in full limp, no throttle for half the pedal travel mode.

There is a cutoff where the ETA connector went from a pancake type to a barrel type. I owned a 1993 400E and it had the earlier pancake connector.

 

[gsxr]

There is a cutoff where the ETA connector went from a pancake type to a barrel type. I owned a 1993 400E and it had the earlier pancake connector.

Correct! This is another EPC error... the EPC shows an engine/serial number break, however the actual break point was pre-facelift (pancake connector) on all 1992-93 USA model year, vs facelift (barrel connector) on all 1994-95 USA model years.

 

[The Ry Guy]

Update on my diagnostic progress (or lack there of)...

Using this diagnostic chart and schematic that I found, I measured the voltages and resistance (resistance's?) at the connector for the E-Gas module. Probing the pins for resistance with the module removed was easy. To measure the voltage, I used stiff bell wire, inserted into the appropriate pin slots and installed the module over it, thus approximating a breakout box.




So, given the above data, I have the wrong voltage and infinite resistance while in park, but the other positions are correct, so my wiring and connections would be good then. Bad S16/3 switch then, right?

I dug through my box of W124 400E spare parts and found another S16/3 switch I didn't know I had, however it was spotty on is resistance tests too.

My thinking was then "well, since the values for Neutral are ok, I should be able to start it and Neutral, and the ASR should only fault when I shift to park." Doing that, the ASR light still stayed on when I started the car in Neutral.

Maybe it's the E-Gas module then? (Cause that's the only thing in the list of fault code #2 I haven't checked or replaced). So, I purchased as used E-Gas module on eBay, installed it, started the car in neutral and... same result. (This is where I pull my remaining hair out.)

When turning the key on, the ETA has a few clicks, but no high pitched sounds coming from it. The only code I have on Pin #7 is #2, I made sure there is plenty of slack in the throttle cable, the engine wiring harness is a Dephi replacement, ETA was checked by Beckman, I've checked everything related to Code 2...

I'm at a loss here, what am I missing? Ideas anyone? Seriously tempted to give up, but I know the solution is there, somewhere...

 

[gsxr]

FYI - the resistance values from the NSS are used to tell the E-GAS what gear position is selected. However these do not affect if the car will start in P/N or not, those are separate contacts, the larger terminals on the round switch connector.

The ETA should make high-pitched sounds and some loud clicks during the startup dance. If it's silent, this is pointing back to a faulty ETA (bad internals, not the lead wire).

Note that for pin 7 fault code #2, there are several items internal to the ETA (M16/xxx).

 

[The Ry Guy]

Appreciate the reply gsxr, but I think you misunderstood what I was driving at. I am aware of what pins are what on the NSS, and the ones that I'm concerned with are the two smaller pins, that are internally connected to the different resistors. What I'm getting at, is that the EGAS module is looking for a correct resistance value, or else it will throw a code, go into limp mode and illuminate the ASR light, right? The NSS in my car is giving a correct value (highlighted values in the second photo) when neutral is selected, hence why I started it in neutral. In park, my NSS is open circuit, and when park is selected should turn the ASR light on and throw the code.

When I turn the key on I get two clicks from the ETA, and it starts to whir, but stops. As I said before in this thread, I've recently sent my ETA to Beckman Technologies, where they tested it for me. I was told they had it on their test bench for two days and they found no fault with it, so I eliminated that as a problem. Are you saying that their test was invalid?

I've gone over this list, checked all the switches that aren't in the ETA and all check ok. I even replaced the EGAS module with another one from a W140 that I bought from Ebay. Still nothing. All the wiring from the ETA connector to the ECU looks to be in good shape, no corroded pins or flaking insulation. Where do I go next from here?

 

[gsxr]

Appreciate the reply gsxr, but I think you misunderstood what I was driving at. I am aware of what pins are what on the NSS, and the ones that I'm concerned with are the two smaller pins, that are internally connected to the different resistors. What I'm getting at, is that the EGAS module is looking for a correct resistance value, or else it will throw a code, go into limp mode and illuminate the ASR light, right?

Correct. The EGAS module will read the gear position, and also transmit that to other modules. If viewing live data, in Park, you would see the position as "F" (Fault) since the resistance reading would be invalid.

The NSS in my car is giving a correct value (highlighted values in the second photo) when neutral is selected, hence why I started it in neutral. In park, my NSS is open circuit, and when park is selected should turn the ASR light on and throw the code.

In theory, if the ASR light / limp mode was being caused by the NSS, starting the car in Neutral should not have resulted in a fault light. Then after starting, if you shift to Park, it could (possibly) cause an issue. If you started in Neutral and there was still an immediate fault, to me that indicates another problem besides the NSS.

When I turn the key on I get two clicks from the ETA, and it starts to whir, but stops. As I said before in this thread, I've recently sent my ETA to Beckman Technologies, where they tested it for me. I was told they had it on their test bench for two days and they found no fault with it, so I eliminated that as a problem. Are you saying that their test was invalid?

Good question. I don't know what their bench test entails, but it's odd that you swapped in another E-GAS module with no change. I'm suspicious of your ETA but now that Don Roden retired, the remaining options are expensive.

I've gone over this list, checked all the switches that aren't in the ETA and all check ok.

I'd check the switches inside the ETA next.

I even replaced the EGAS module with another one from a W140 that I bought from Ebay. Still nothing. All the wiring from the ETA connector to the ECU looks to be in good shape, no corroded pins or flaking insulation. Where do I go next from here?

Ideally, the next step would be connecting a digital scanner so you can pull the 3-digit digital fault codes, which are more specific vs the analog codes. However, even those are not fully discrete (some digital code can have more than 1 meaning). Viewing live data may help but only if whatever is wrong is something you can see in live data.

Normally I would have the ETA at the top of the suspect list, but since Beckmann said it tested OK, I'm puzzled. I'm still not ruling it out though.

 

[rayhennig]

The NSS I have in stock was bought from Porsche, 65€ against 95 at Mercedes.

Assuming it's the same part as mine, you might strike lucky with Porsche.

RayH

 

[Jlaa]

The NSS I have in stock was bought from Porsche, 65€ against 95 at Mercedes.

Assuming it's the same part as mine, you might strike lucky with Porsche.

RayH

Do you have a Porsche part number? Does it start with 928-?

Thanks

 

[rayhennig]

Do you have a Porsche part number? Does it start with 928-?

I shall have to look. I can't remember but I do recall that it also had the MB number.

I'll report back tomorrow. I'll send a photo of the box but the part itself is definitely MB.

R

 

[rayhennig]

Do you have a Porsche part number? Does it start with 928-?

Thanks

Completely forgot. Dementia setting in!





Don't see 928 there but I do recall that the 928 uses an MB gearbox. Others will know better than I.

R

 

[gsxr]

Porsche p/n 000-545-490-6 seems to correspond to MB # 000-545-49-06 which will not work for the 124.034/036 chassis, it lacks the additional 4 small pins for gear position output.

 

[rayhennig]

Porsche p/n 000-545-490-6 seems to correspond to MB # 000-545-49-06 which will not work for the 124.034/036 chassis, it lacks the additional 4 small pins for gear position output.

Mine is an M104.980 + 722.5 box. Can't comment on the 500s.

Sorry.

R