Throttle body woes

[LaugeR129]

Hope somebody can give a little insight or advice to a problem with the ETA in my 1993 R129 with ASR (m119.172 engine).

The car has been parked over the winter and upon starting the car for the first time after 6 months it went into limp mode. Tried restarting the car a few times and limp mode every time. When I turn the ignition on an I get a short click from the ETA, no humming afterwards and only limp mode.
So before even touching the throttle it fails.

So started Xentry and HHT to read the fault codes.
The codes are:
EFP: Error 048 (Set value potentiometer. Potentiometer monitoring M16/1r1).
ASR: Error 030 (CAN: No reception from EFP N4/1)

My first thought was that the ETA wiring, that I myself redid approx. 4 years ago, might have gone bad. I did a little work on the car during the winter so maybe I pulled a wire. Took the ETA out and opened it and measured all the connections from the end of the plug to the circuit-board in the ETA. All good, hmm.

My next thought was that the potentiometer might have gone bad when the car was parked. So ended up buying a used ETA from ebay, with what seems to be good original wires (the cover for the wires was cut open by the selling showing good wires), and described as working by the seller. Plan was to have it rebuild next winter.

Plugged in the new ETA, but I get exactly the same error code. Of course, both ETAs can be bad, but exactly the same error code seems unlikely to me. My next thought was the EGAS module. Have a friend with a W140 m119 so we tried putting my module in his car. His car works fine with my EGAS module, and my car has exactly the same error as before with his module. So seems like the EGAS module is ok.

My next thought was maybe there’s a problem with the wiring from the ETA plug in the engine bay to the EGAS module. So pulled the EGAS module and measured all the connections from the back of the circuit board of my old ETA to the EGAS module plug at the bottom of the computer box. All connections seems ok and there doesn’t seem to be any shorts.

Other info:
The battery is only a year old and it’s been on a charger all winter. Have also tested the car with the charger on so battery voltage shouldn’t be a problem.
Checked the 4 fuses on the GM module.
Reseated the EGAS module a few times.
The NSS is probably old but shows the right gear in HHT when I move the selector. (Strangely my friends NSS is shown as failed in HHT but his car drives fine).
Upper wiring harness has been changed, lower is still original. (Don’t think upper or lower is relevant from the fault)
It fails with the ETA out of the car but plugged in, so don’t think it’s the throttle linkage.
I can’t test the ETA on my friends car, since his ETA uses the old pancake style plug. Otherwise that would be the best test.

EFP Actual values:
With old ETA:
M16/1r2: 4.38v
M16/1r1: 0.02v

On the "new" ebay ETA:
M16/1r2: 4.34v
M16/1r1: 0.19v

I think the M16/1r1 should be approx. 0.50v.
Does anyone have any ideas to what could be wrong? Is it really just my bad luck to have to failed ETAs with the same failure? Is it a common failure? Would it make sense to test the ASR, LH and GM module from my friends car?

And if the ETA is bad does anyone know of a place in the EU that does good work on them? Most of the repair places seems to be in the US, and I think that’s a major problem with shipping and taxes.

I have an MOT coming up in june and it's a quite a hassel if I don't get the running before that. Plus I would also like to actually use the car.

Hope somebody here as a good suggestion.

Thanks in advance

Lauge

 

[frall]

Really interesting.
Can you make pics of all the EFP HHT-Win pages?
Check the switch on gas pedal at first (in HHT-Win you should see it switching). S29/3

 

[frall]

EFP Actual values:
With old ETA:
M16/1r2: 4.38v
M16/1r1: 0.02v

On the "new" ebay ETA:
M16/1r2: 4.34v
M16/1r1: 0.19v

M16/1r1 should be more than 0,23 V at idle.
Probably you have two bad ETAs

 

[gsxr]

EFP (E-GAS) code 048 is specifically for the internal potentiometer in the ETA. Sounds like you have 2 bad ones. Really need to have one professionally rebuilt. I don't know EU sources but you can try Don Roden at RFC Electronic here in USA, search the forum for contact info. Without a known-good & tested ETA, it's difficult make progress.

ASR code 30 is a default code that appears almost every time with limp mode. Don't worry about that one.

 

[LaugeR129]

Really interesting.
Can you make pics of all the EFP HHT-Win pages?
Check the switch on gas pedal at first (in HHT-Win you should see it switching). S29/3

Thanks a lot frall and gsxr for the replies, really appreciate the help

I have again testet both ETAs. Not at idle, but only with ignition on, since the ETA is not mounted in the car.
Think the most interesting is the “ebay_ETA_EFP_page_2_IDLE” with the throttle arm resting at idle. And “ebay_ETA_EFP_page_2_FullThrottle” with the throttle arm at full throttle just before ETA is manually activated. Comparing to the “old_ ETA_EFP_page_2_IDLE” and “old_ETA_EFP_page_2_FullThrottle” where the M16/1r1 value actually changes – however only just before full throttle.

If I push past full throttle and manually activate the throttle flap (limp mode) the 09 and 10 safety contacts switch values.
In “old_ETA_EFP_page_2” the “08 Idle speed contact sw S29/3” goes from OFF to nothing at full throttle. Don’t know if that a HHTWIN bug.
The files with prefix “both” are because they have exactly the same values with both ETAs.

So frall and gsxr are probably right it two bad ETAs. And just from the numbers the ebay one might even be worse since M16/1r1 doesn’t change at all.

I did notice that the ASR (ASR_Page_3) shows “11 Stop lamp switch N.C. contact” as ON whereas the EFP shows OFF. Don’t know if that’s important and don’t think it’s related to my ETA problems.

Does anyone know how important the part numbers of the ETAs are? Are other numbers ok to use. I know there’s two kind of plugs but besides that, there’s a lot of different numbers when searching. Because it might end with me having to purchase another one used just to clear the MOT, while a figuring out a way to get the old one rebuild.

 

[gsxr]

Voltages for M16/1r1 and M16/1r2 should change proportionally (approximately) as you slowly move the throttle from fully closed to fully open. If both values are not changing with pedal movement, those potentiometers have issues (assuming the E-GAS module and wiring are ok).

The 3 contacts shown directly below will change from Off/On/Off, to opposite... On/Off/On, when you move the pedal from idle to roughly half throttle. This sometimes takes a few seconds to register, the digital communication is slow. If you don't see these values change properly, one of the contacts may have issues as well.

Since your car is an R129, I don't know the wire length of the ETA. You can use an ASR ETA from a 124 or 140, IF the wire is the same length or longer. You can't use a non-ASR ETA, an ETA with a different connector, or with a shorter wire.

 

[LaugeR129]

Voltages for M16/1r1 and M16/1r2 should change proportionally (approximately) as you slowly move the throttle from fully closed to fully open. If both values are not changing with pedal movement, those potentiometers have issues (assuming the E-GAS module and wiring are ok).

The 3 contacts shown directly below will change from Off/On/Off, to opposite... On/Off/On, when you move the pedal from idle to roughly half throttle. This sometimes takes a few seconds to register, the digital communication is slow. If you don't see these values change properly, one of the contacts may have issues as well.

Since your car is an R129, I don't know the wire length of the ETA. You can use an ASR ETA from a 124 or 140, IF the wire is the same length or longer. You can't use a non-ASR ETA, an ETA with a different connector, or with a shorter wire.

Again thanks

It helps knowing other part numbers can be used, since it makes it easier finding a used units. I'll probably end up contacting Don Roden.

Right now I just need to sort out the complaint with the bad ebay unit. And I'm contacting the dealer to hear if a new ETA is still available.

I’ll of course give an update when there’s anything new.

 

[frall]

You can see at the attached picture, that there is a difference between your ETAs and my at the Sollwertpotentiometers. The Value 07 must be over 0,23 V. It is the inside potentiometer.

If you are interested, you can send it to me (Germany) and I will have a look at it. Probably I can repair it as I did several times before.

 

[LaugeR129]

You can see at the attached picture, that there is a difference between your ETAs and my at the Sollwertpotentiometers. The Value 07 must be over 0,23 V. It is the inside potentiometer.

If you are interested, you can send it to me (Germany) and I will have a look at it. Probably I can repair it as I did several times before.

That could be a really good solution for me I have started a conversation here on the site with you. Think we can just do the details in private and not in the thread.

Btw just got reply from Mercedes, that the ETA is not available new. Not surprised at all, but they did show it as being in stock when I checked online, so worth the try.

 

[LaugeR129]

I just want to post an update – the short story is the car now works and it was a faulty ETA.

The long story is the trouble shooting and repair ended up being a lengthy process.

I took Fralls offer and shipped both units + e-gas module to him in Germany. Frall was really quick at repairing both ETAs and explaining what was done. They were both faulty. As I understand the ebay unit was not assembled correctly, so the ebay seller was probably not truthful in the description of the unit as being removed from a working car. My old unit had some corrosion. Frall fixed both units, cleaned them and shipped them back, saying the Ebay unit was the best one.

Mounted the ebay unit. When mounting the unit my elbow hit the plastic adjustment screw on the throttle cable. Being 28 years old plastic it broke. I know the cable adjustment is really important, so knew I had to replace it. But took a short test-drive anyway. No limp mode, pulled fine, but at light throttle the engine would cut out around 1100 rpm. But idle was perfect so knew it wasn’t rotors and caps. My thought was it was probably the broken throttle cable. So new cable and adjustment – and exactly the same fault. Hmm. Then tried the other ETA from Frall – same fault. Read codes and e-gas had: Error code 182 “Safety fuel shut-off switch for LH N3/1”. So emailed with Frall back and forth, to rule out it wasn’t an assembly error. Frall was really helpful with lots of ideas and documents. He also showed pictures of the safety switches and so on. The HHTWIN didn’t show the correct safety switch positions, but some say the readout of safety switches is a bit buggy. The car never went into limp mode, but there was clearly a fault.

I removed the gas pedal safety switch to check that part out. Worked fine. Then thought maybe the e-gas module was damaged in shipping to and from Germany. So tried my friends e-gas module, but it’s from a w140 so HHTWIN wouldn’t read codes from it – but the drivability problem was the same and the fault was still there.

Finally, I checked the ETA plug. Remember I measured all the wires from the back of the ETA circuit board to the e-gas module before shipping the units to Frall. So I was certain the wiring was ok and plug was ok. But as a last resort I checked the plug and one of the pins was loose. It looks fine but it’s broken at the bottom and can be moved around – will probably break completely of if it’s touched anymore. So I sourced a replacement plug and mounted it. And now the gas drives perfect. Really smooth idle, drives fine, no codes.

So the short recap is:
ETA goes bad with the car standing still over winter.
Second ETA has exactly the same fault is the first one (what are the odds?)
Don’t hit your elbow old plastic
The second fault with the bad pin in the plug is probably caused by me tried both units and unplugging them several times – maybe the pin was bad before, but worked, and then it’s gotten worse with the plug in used.

I am really happy the car drives well now. Thanks to everyone for help and suggestions. It’s really a great forum. And a big thanks to Frall for the work with the ETAs and help afterwards.

Not sure how much others can learn from this. But I was surprised the broken pin didn’t give limp mode but just fuel cut off. The car was much more drivable than in limp mode.

 

[Duh_Vinci]

Cheers and thank you for your follow through, appreciate it! Glad you were able to sort it out and found a solid source to repair your ETAs!

I have 1995 R129, and luckily, the throttle body was rebuild by original owner, so was the upper harness (had many many other issues, but all sorted out now). I do have to rebuild the lower harness still. In time...

Regards,
D