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300 CE 24V Sportline
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Discussion Starter #1
Hello all,

And a challenge.

5th gear disappeared again. What have I done to investigate this:
  1. Replaced microswitches under gear lever. Confident that all's OK here.
  2. Cleared 4 flash fault code: “Throttle valve switch (potentiometer) interrupted.”
  3. Drove 8 km to refuel and 5th has gone again.
  4. Checked microswitch again - seems OK. Now cannot clear fault code.
  5. Several days without 5th.
  6. Colder this morning (clue?) drove off and we have 5th.
  7. But not for more than 15 km. It’s gone again.
Is this temperature-related? The first time failure did seem to be in very hot summer weather.

I can say more, much more, on this but shall await initial feedback.

Best to all.

RayH
 

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R107 300 SL, Year 1986 and C124 300CE-24 Year 1990
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125 Posts
Hello Ray,

maybe the HGS Relay A008 545 66 32 (in my 1990 300CE-24) next to the Battery has a cold solder joint, or bad contacts
 

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Discussion Starter #3
Hello Ray,

maybe the HGS Relay A008 545 66 32 (in my 1990 300CE-24) next to the Battery has a cold solder joint, or bad contacts
Thanks for that. Yes, possible, but in mine the HGS is just under the steering wheel, inside the car. With the recent temperature changes - summer 40C to 10C - it seems unlikely.

It seems more likely to be something that's heated by the engine or gearbox. That 4 flash code (Throttle valve switch (potentiometer) interrupted) is consistent and leads me towards the potentiometer. I have a replacement but have not yet tried to replace it.

Thanks again.

R
 

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1992 CE 300-24
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40 Posts
Hi Ray, I also have a CE 300-24, a right hand drive `92, with the 722.5 auto,
& while USA didn't get CIS 124 5-speed automatics, they did get both R129
300SL (chassis based on 124), & the W140, just so equipped.

The W140 section here has a freely checkable 'Startek' link which will enable
you to run through a driving operation fault diagnostic cascade for this
combination which also directly relates to our CIS/722.5 fitment CE 124s.

Ironically, I've been chasing a 'phantom' 4th gear non-selection issue, & read
your problem solving posts with interest, but having replaced the relevant switches
& overload protection sensors/relays, & checking mechanical functions, finding
it still shirks its duty, hurriedly handing over to 5th/O-D, regardless, is a bugger...

Perhaps your problem is related to the overload protection pressure transducer,
on the side of the box above the pan, (which is cold temperature sensitive),
& or/the associated wiring (plus the dreaded EZL* die-off syndrome?).

I am at the point of checking the wiring from the same unit (given its a new M-B brand item),
through to the control module, as a code 9 fault will indicate, according to the diagnostics.


* Re CIS M 104 EZL, a US company offers a rebuilt unit with a year's warranty
for US $399- (& I've been told that CIS V12 EZL units are cross-compatible).
 

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300 CE 24V Sportline
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Discussion Starter #5
Hi Ray, I also have a CE 300-24, a right hand drive `92, with the 722.5 auto,
& while USA didn't get CIS 124 5-speed automatics, they did get both R129
300SL (chassis based on 124), & the W140, just so equipped.

The W140 section here has a freely checkable 'Startek' link which will enable
you to run through a driving operation fault diagnostic cascade for this
combination which also directly relates to our CIS/722.5 fitment CE 124s.

Ironically, I've been chasing a 'phantom' 4th gear non-selection issue, & read
your problem solving posts with interest, but having replaced the relevant switches
& overload protection sensors/relays, & checking mechanical functions, finding
it still shirks its duty, hurriedly handing over to 5th/O-D, regardless, is a bugger...

Perhaps your problem is related to the overload protection pressure transducer,
on the side of the box above the pan, (which is cold temperature sensitive),
& or/the associated wiring (plus the dreaded EZL* die-off syndrome?).

I am at the point of checking the wiring from the same unit (given its a new M-B brand item),
through to the control module, as a code 9 fault will indicate, according to the diagnostics.


* Re CIS M 104 EZL, a US company offers a rebuilt unit with a year's warranty
for US $399- (& I've been told that CIS V12 EZL units are cross-compatible).
Interesting stuff. And a pity that the switch changes didn't bring back 4th.

Yesterday, 5th was missing from the outset so I don't know what to think about that. I still return to 4 flash code (Throttle valve switch (potentiometer) interrupted) as that has been consistent throughout. Any thoughts from you on that?

I note what you say about the "overload protection pressure transducer". Do you mean part 303: A0025454514?

2658241


Does that influence only 5th? I ask because my gearbox has been rebuilt and really works like new. When 5th is working, it's perfect. Otherwise, it's perfect on 4 gears. Any comment there?

Regarding EZL issues, I have no evidence to point at that. But who knows. My car killed 3 EZLs from July 2019 to 12th June 2020 (my birthday - some present!). I have 2 spares: one secondhand from Guernsey (Channel Islands) and one new (made in 2003!!!) from MB in Germany. Both verified as working.

I've seen these rebuild offers but the price seems to approach the 1100 € I paid for the new one (tested but not installed).

And so it continues.

Great to hear from an Ozzie.

As ever.

Whinging Pom.
 

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1992 CE 300-24
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40 Posts
Ta for the welcome Ray.
Chasing electrickery gremlins can be a frustrating game.

Click on: W140 S-Class

Then scroll down to 'Hot links W140 Forum STAR TekInfo Manuals'

Click on: STAR TekInfo > Chassis & Drivetrain > Volume 1 > ETC
(Electronic Automatic Transmission Control) > 2.1 Model 129 with CFI (722.5)
13/1 Complaint Related Diagnostic Chart.
I note it mentions your Fault Code 4 as a potential issue, so it may be a
simple matter to sort, & for which you already have the part on hand.

On other pages it notes the temp-sensitive overload protection switch
(which I listed as a transducer) & its associated wiring as a potential problem.

Here is a link to the EZL rebuild I mentioned previously.


Best wishes with a fix.

James.
 

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300 CE 24V Sportline
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Discussion Starter #7
Ta for the welcome Ray.
Chasing electrickery gremlins can be a frustrating game.

Click on: W140 S-Class

Then scroll down to 'Hot links W140 Forum STAR TekInfo Manuals'

Click on: STAR TekInfo > Chassis & Drivetrain > Volume 1 > ETC
(Electronic Automatic Transmission Control) > 2.1 Model 129 with CFI (722.5)


I note it mentions your Fault Code 4 as a potential issue, so it may be a
simple matter to sort, & for which you already have the part on hand.

On other pages it notes the temp-sensitive overload protection switch
(which I listed as a transducer) & its associated wiring as a potential problem.

Here is a link to the EZL rebuild I mentioned previously.


Best wishes with a fix.

James.
Great stuff James. Thanks.

COVID lockdown here so testing might be risky.

More as it happens. I hope.

R
 

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1992 CE 300-24
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40 Posts
Hi Ray, I'm in the process of mapping out a component test plan,
& in post #3 above you've located the RHD HGS unit (for 5th gear):

"...just under the steering wheel inside the car."

Can you please be a bit more specific, I've pulled the plastic under-tray,
which fits under/seals off that area below the dash/above the foot-well,
but could not locate any evidence of major plug units fittings.

So I now ask, is the HGS located in the the screwed down plastic box just
behind the main fuse box, in the same space at back of/under the right bonnet
compartment (on the driver's side), with the duo-valves/vacuum manifolds, etc?

(Here's a weird thing, I tried the 'shade-tree' fault clearance technique of
an overnight off-battery terminal tie-together with ign' set in the on position,
& while it didn't make my recalcitrant 4th gear step in for duty, it def' did
make the whole engine/trans interface much more responsive/peppy!)

Ta, J.
 

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300 CE 24V Sportline
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Discussion Starter #9
Hi Ray, I'm in the process of mapping out a component test plan,
& in post #3 above you've located the RHD HGS unit (for 5th gear):

"...just under the steering wheel inside the car."

Can you please be a bit more specific, I've pulled the plastic under-tray,
which fits under/seals off that area below the dash/above the foot-well,
but could not locate any evidence of major plug units fittings.

So I now ask, is the HGS located in the the screwed down plastic box just
behind the main fuse box, in the same space at back of/under the right bonnet
compartment (on the driver's side), with the duo-valves/vacuum manifolds, etc?

(Here's a weird thing, I tried the 'shade-tree' fault clearance technique of
an overnight off-battery terminal tie-together with ign' set in the on position,
& while it didn't make my recalcitrant 4th gear step in for duty, it def' did
make the whole engine/trans interface much more responsive/peppy!)

Ta, J.
WhatHo,

Just to clarify: mine is LHD (we're in France) so things may be different to your RHD. I removed the trim under the steering wheel when we renewed the ignition lock. I was also trying to fix the brake/gear lever lockout not, er, locking out.

So, given that the wiring from the throttle body to the HGS, on mine, disappears into the car, behind the engine, on the left (when driving) side of the car, I would guess that your HGS might be under the dash board on the PASSENGER side.

By the way, I need a favour. Can you picture the round, 3-pin connector, from the throttle body, to the HGS, where it plugs into an extension cable alongside the engine? It's the round one in the picture:

2658881


My connector is broken in places but making good contact. However, any keyway that enabled only the correct way to connect has long since worn away. Mine will plug into the extension in any of 3 ways.

So, please could you look at yours and try to identify where I locate the arrow on the throttle body connector locates on the other connector.

Yet more work but we're in COVID lockdown here so I may have time on my hands.

Bonne chance.

RayH
 

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1992 CE 300-24
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Yeah ta Ray, that HGS location does seem reasonable, I'll keep on looking...

Now, about your ask:

Funnily enough, that particular 3-pole connector is one I've checked recently,
(& guess what, the aged plastic connector clips fell apart in my fingers, too!).

However, if you check the Star tech Info manuals linked on the W140 thread,
& go to Vol 1, 'Chassis & Drivetrain' & then > '2.1 Model 129 with CFI (722.5)'
scroll down to 'Electrical Test Program' > 'Preparation for Test' > click on 22/1,
& scroll down, that 'TB switch AP Potentiometer' - correct alignment - is shown.

Hope that helps, J.
 

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Discussion Starter #11 (Edited)
Great, I'll give it a try.

I have the picture, now to remove the air filter and have a look.

More as it happens.

By the way, having plugged it in by guesswork, 5th failed to make an appearance when I went to stock up on "lockdown booze"!

R
 

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1992 CE 300-24
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40 Posts
Hi Ray, further to my previous reply, I've been checking through the
M104 CIS/CFI data linked here in the W124 DIY 'sticky', & via the
'Online Manual with Index', I've found some more items of interest.

I've been cleaning the wiring/component plug connections & Tried
the 'shade tree' overnight fault code clearance trick/protocol of an
systems energy drain by dint of main power terminals off-battery
& tied together with the ign' switch in the full-on position.

Annoyingly it didn't make 4th gear do its duty, but it sure made a
very obvious pep-up in performance, both if held in gear, & in 'D',
with re-set upshift points, & also, 1st gear start!

I've bought a suitable LED to do some bloody, ah, blinking, code
fault checks/erasure, & have a new O.D. to ECU electric cable on
its way, to mayhaps winkle out that recalcitrant 4th gear, yet.

& Ray, since you have a number of EZL units on hand, can you
check the marking codes on the plug in 'reference resistor'* &
check whether they are the same?

*The 'reference resistor' is the only plug in unit on the EZL
which does not have a lead attached (electrical/vacuum).

Ta, James.
 

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Discussion Starter #13
can you
check the marking codes on the plug in 'reference resistor'* &
check whether they are the same?
Hello from sunny France.

The plug-in resistors on mine are all, and have always been, No. 2. Ref. 0155458??9 or 0155456728. Can't read the 2 digits on the first one but, I think, No. 2 is the important issue.

This plug-in resistor adjusts the timing curve to meet the needs of varying fuel octane, I think. I have sometimes removed it (to advance), changed from 95 to 98 octane and noticed no difference.

But there's also this to consider:

But 124.051 not mentioned.

Shall think more.

Does that answer?

R
 

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1992 CE 300-24
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40 Posts
Yeah, ta for that Ray, same part number here,
& since my component connection clean/refit
the engine def' runs more smoothly too, with
a real even idle that had me eyeing the tach
to see if it had stalled.. In Australia, we got
the 'hot' climate set-up with emission control*
is yours a 'kat' (catalytic converter) unit too?

Apart from the exhaust 'kat' restriction issue, manual
box M104 CIS/CFI engines are sometimes noted to
be a few hp more powerful, (as are the R129 SL300s) but
apart from cam/ignition timing tune via the EZL, is there
any other form of actual mechanical difference,
that you are (or any other member) aware of, Ray?

* Not California extreme though, thankfully.
 

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Discussion Starter #15
Mine is a Kat version owned by a business man who lived in Monaco and worked in Paris. Word has it that the car only burned up and down the autoroute between home and work. This for 7 years before I bought it.

Yes, I've heard that non-kat versions develop 231 bhp versus 220 for the kat version.

My other unanswered question is differences between the M104.980 in all cars but the 300SL that had the M104.981, always quoted as developing 231 bhp. No idea why the extra as many SLs are kat versions.

R
 

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R107 300 SL, Year 1986 and C124 300CE-24 Year 1990
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Hello Ray,

the R129, 300 SL-24 has the M104.981 with 231 hp because they have a different exhaustsystem as the 300 CE-24 M104.980 in my Coupe with 220 hp. As far I know all a KAT was installed in all 104.980 (1) engines.
 

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1992 CE 300-24
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40 Posts
Well, I made a perusal of the R129 SL300-24 exhaust,
& even the 'kat' set-up looks different (less restrictive on
the O2 sensor 2-1-2 pipe bifurcation), so that's something.

I also checked out a '231hp' Brit-spec 722.5 CIS CE-24 - sans kat
set-up (inc' smog-pump) - & yeah, it has a different EZL ref' plug, too,
with the big number being 5*, (mine is a 3, not a 2, like yours, sorry).

I might see if I can get a swap-trial of that & the HGS 5spd trans unit,
& see if it makes my still shirking 4th gear, step in for duty.

*AFAIR, ( I should've noted it, since now I'm wondering if it wasn't a
2, upside down)...
 

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Discussion Starter #19
*AFAIR, ( I should've noted it, since now I'm wondering if it wasn't a
2, upside down)..
Sounds more likely given the spec of your car. The higher the number, the lower the resistance, if I recall correctly. So, when I remove the plug, infinite resistance gives greatest advance.

I think those higher numbers (lower resistance) retard ignition for use with rotten US fuel - <95.

I'm not 100% certain and too busy with real life right now to delve further today.

R
 

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That's cool R, ta for the 'heads up' on the number codes.

The No 3 plug downunder must be a retard emission control
thing, (along with a hotter spark plug grade) but a bit odd,
because '98' hi-grade petrol is readily available here.

Do you you know if running/driving sans the plug kills the EZL?

I've just found my 5sp HGS/TCU behind the left side kick panel,
so I'll do a contact clean & wire/plug in continuity trace on it.

& I've bought a new 5th gear solenoid 'pigs tail' wiring plug (that fits
in situ within the trans pan) & I'll check if it has been wired up inside
out of phase, (to effectively skip/delete 4th selection, instead of 5th),
according to the colour-coding on the wiring diagram, as it may be a
possibility, since the mechanical/hydraulic trans functions do check out.


(If the No 2 ref' plug does make a difference when I trial it, R,
any chance you'd possibly see your way clear to popping one
out of a dead EZL you have on hand, & sending it my way, perhaps?
I'll pay for postage, & etc, no worries - if you'd PM me with details).

Ta, J.
 
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