W124 E280 4 Spd Auto (Est), Cruise Control

JensH

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Mornin' all,

Cruise control on my car has been U/S, since I got it back in October. It is next on my list to restore to working order. I will then only have 3 main issues, apart from a list of largely cosmetic cabin and trim parts, which I'll do gradually, (1) o/s heating & A/C issues (prob. matrix), (2) underbody mechanical inspection & overhaul, and (3) bodywork, including new wings and load bay side window trims.

On the CC there is no response at all from the stalk control.

I am on the EPC so have a good idea of the exact system. My car was a pretty late model, leaving the factory on 17 November 1995 (with free factory A/C). I have a CC-specific wiring diagram and print out of drawing and part list from EPC. This thread won't therefore be too much use to owners of earlier 124s because late models have very different layouts of the CC system (see my control module below).

It is the ISC (Idle Speed Control) Type, without ASR (traction control). Confirmed direct by MB.

My understanding is that the following components are all capable of failure:
Fuse: No. 5, terminal 15;
Fuse: On N7, exterior lamp failure monitoring unit (in relay casing at back of engine bay, relay code K);
Connections: Anywhere in the system;
CC Harness: Part A 124 440 20 09 (connects main system components);
Secondary harness, brake light switch to bi-connection: Parts A 124 540 24 08 and A 124 440 99 08;
Tempomat stalk switch + cable/connector: Can't find part number for this?
B6 Hall-effect speed sensor: Part A 007 542 29 17 (sits on back of instrument cluster);
X53/5 Hall-effect, multiway connector; Can't find part number for this? But only needed if more than one vehicle system needs to use the H-E sensor. I have one fitted (fixture at back of instrument cluster void);
N4/2 CC Module: Part A 124 545 51 32 (mine sits mounted at rear of engine bay, passenger side, under its own flexible cover, immediately behind battery);
M16 CC Actuator: Can't find part number for this? (Mine is attached under the manifold intake cover);
Linkage, actuator to throttle: Can't find part number for this (attached to actuator).

My first question is could some tell me either (a) where on the EPC I will find the parts which I haven't been able to find specific to my VIN or (b) the part numbers for the 4 I am missing, stalk switch (+cable/connector), X53/5, M16, linkage.

Second question is two-fold: what is the logical and most efficient testing sequence for fault-finding? Will the main components show up with a blinking diagnostic reader?

I have a working external temp gauge, which I think means that I have no issues with B6 or X53/5.

With a full bank of parts data and advice on method, I will investigate, including cost of MB supply v breakers.

Cheers,


Jens :)
 

mej

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I was sure that on these (mine was a 124.088) HFM engined models, the CC was calculated by the ECU behind the battery. Two plugs lead cabling out of this, and one connects (amongst others) the throttle body with its potentiometers and throttle actuator motor. Hence no separate CC actuator or dedicated ECU. Mine now sold, so can't check physically.

I have some docs on this, but too big to attach. PM me an email address if you wish to have them.
 
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JensH

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124.088 Cruise Control N4/2 Module

I was sure that on these (mine was a 124.088) HFM engined models, the CC was calculated by the ECU behind the battery. Two plugs lead cabling out of this, and one connects (amongst others) the throttle body with its potentiometers and throttle actuator motor. Hence no separate CC actuator or dedicated ECU. Mine now sold, so can't check physically.

I have some docs on this, but too big to attach. PM me an email address if you wish to have them.

Thanks for this,

That all makes sense - would explain why I couldn't see a connector to the actuator! So far, I had assumed it was fitted to bracket on or near the manifold.

The EPC diagram has what looks like an actuator on the drawing, but no part number specified for it, but with a shaded off connector, which I now see is consistent with no actuator. I haven't actually had the manifold intake cover off, so I made the wrong assumption there. The part that EPC does show on the same harness node is a 4mm round pin bushing, which is, I assume, the connector to the throttle body?

So if its all controlled by the ECU that will be both no actuator and no linkage? 2 fewer things to worry about, then!

It is definitely an N4/2 control module. I'll send you a PM re the docs you kindly offered.

Thanks,


Jens :)
 
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JensH

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Cruise Control Update 14 March 2014

I have now identified all my relevant main CC parts (for a late '95 E280 4 speed auto, 124.088, 104942 engine) as follows (with designation codes, as used in WIS, in brackets)
Tempomat Switch (S40): A 124 540 09 44
Hall Effect Speed Sensor (B6): A 007 542 29 17
Hall Multiway (X53/5): A 124 540 03 69
Throttle Valve Actuator (M16): 000 141 65 25 (Idle Speed), & 000 141 57 25 (CC), both housed in the same component under the air mass sensor assembly for the injection system
Control Module (N4): 124 545 51 32 (4 speed auto)

So there is definitely an actuator component.

I know that there are other minor components in the CC system, but since my wiring appears ok, I am thinking one or more of the above has failed?

So, television, will your little blinker reader give me clues as to which component is at fault, and, are you sure (I think you are!) that late Euro W124's were definitely NOT OBD2 operational? I see my car actually has several W210 parts around the engine bay, so assume that there was some transitional upgrading on the late W124s... So perhaps they were OBD2 compliant?

Jens
 
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JensH

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W124 '95 E280 Auto (Est), Cruise Control, Update...

Hi all,

Yesterday I accessed the diagnostic box, socket 14, and got the following codes relating to cruise control from a reader:

2 = CC/ISC Module
4 = CC Switch
5 = Stop Lamp Switch
10 = Engine speed (RPM) signal (TNA)

Is it likely that if I change the CC CU (A124 545 51 32, part number for a 124.088), the other faults may be corrected?

I know where all the parts are, but I wondered whether the CPU might be the root of all the problems?

Cheers,


Jens
 

Triv

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Replace item 3 on your list (numbered 5) first,, then if necessary item 4 (numbered 10).
I know little about 124's but if stop lamp switch comes up, that's generally your culprit.
I don't think you'll spend much money on one so, the usual thing about diagnostics saving you money spent on guessing and just replacing parts willy nilly, doesn't really count.
:D
 

mej

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Hi Jens

I suspect your throttle body potentiometers are innop, requiring a new throttle body from a scrapper (not prohibitive). That's 2 and 4 IMO. May be simply the cable, but easier to replace the whole thing than rewire. The stop lamp switch may be u/s as says Triv. On some models simply a dodgy stop bulb can affect the cruise I've heard (but not suffered this myself on my 124.088). The engine speed signal, item 10, is from the CPS (crank position sender) which has a connection behind the battery area on your model. Might be worth checking this. You may also be able to confirm at this connector that the CPS is sending a correct signal. The attached doc may help. I'm not suggesting replacement at this stage. If you have the EPC you also have the WIS, which may give signal ranges for the CPS.
Finally I would consider a self rewire of all the loom as discussed earlier and in other posts of mine on this forum and other MB/W124 ones.
 

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television

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I have 3 faulty 124 cc ecu amps here, never could find out what fails on them
 
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JensH

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Thanks alls!

For these very helpful bits of information. :cool:

I will look again at all the Tempomat harness connections, although my wiring overall seems to be in pretty good shape, with some earlier attention...

Had a look under the R/H dash yesterday, to do a photo survey of the bits, only to discover a unit which I never knew was there - some kind of CU for the Tempmatik (a Modulo 875240 ECU 12V, about which I can find out zip! I'll follow that up on my other thread. :confused:

Malcolm, I may shortly be able to let you have a fourth non-functional CC CPU for your collection... ;)

Have a nice Sunday. :)
 

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