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View Full Version : Bosch LH-Jetronic (LH 4.1) - Pinout Guide Needed



BigWillieStyle
12-05-2015, 11:30 PM
Here's a reference of what I'm looking for, the example below is for a predecessor LH-Jetronic System, LH2.4 with 35-pins.

45100

On the LH4.1 I see two banks, one for 38-pins, and one for 41 pins, and the twin isolated dual-pin in the corner? Let me know if I'm missing something, theres a lot of chatter about OBD pinout to run diagnostic codes but I don't want to assume that the literature is 100% transferable.

45101

Much appreciated!

gsxr
12-06-2015, 09:12 AM
Just curious - what exactly are you trying to do? The diagnostic codes are available from the 38-pin connector, no need to mess with individual pins on the module.

:cel:

BigWillieStyle
12-06-2015, 07:19 PM
Thanks! YDM!

Just for clarification YDM is "You da Man" and not "Yugoslavian Domestic Market"

Sent from my Fire Phone using Tapatalk

BigWillieStyle
12-07-2015, 12:11 AM
Apologies, earlier on the fly didn't see your inquiry... See the attached image.

45110

I'm comparing to MS3 pinout schematic, trying to work this whole thing out in my head, but more importantly on paper as well.

Efraim
12-07-2015, 08:16 AM
Hi,
There seems to be pin for "Fuel consumption display" in LH box. Has anyone studied about this pin? Is it possible to install fuel consumption gaude to W124.036?

gsxr
12-07-2015, 09:06 AM
There seems to be pin for "Fuel consumption display" in LH box. Has anyone studied about this pin? Is it possible to install fuel consumption gaude to W124.036?
It's probably for the trip computer, which was optional on European models, and quite rare.

:scratchchin:

Efraim
12-07-2015, 12:40 PM
It's probably for the trip computer, which was optional on European models, and quite rare.

:scratchchin:
w129/w140 have fuel consumption gauge as standard and with M119 they shares the same LH box. The gauge must have a signal about fuel consumption, while the LH box is the most obvious source for the signal.

gsxr
12-07-2015, 12:49 PM
w129/w140 have fuel consumption gauge as standard and with M119 they shares the same LH box. The gauge must have a signal about fuel consumption, while the LH box is the most obvious source for the signal.
IIRC, the W140 "fuel consumption" gauge is just a vacuum gauge... and not particularly accurate. However, I may be incorrect, I'm not that familiar with the W140 or R129 clusters.

:blink:

Klink
12-07-2015, 03:19 PM
IIRC, the W140 "fuel consumption" gauge is just a vacuum gauge... and not particularly accurate. However, I may be incorrect, I'm not that familiar with the W140 or R129 clusters.

:blink:

Nope. the 129 and 140 consumption gauges are actual consumption gauges and they are pretty accurate. The LH fuel consumption signal is for 129, 140, and possibly the 124 with the optional trip computer...
:klink:

Klink
12-07-2015, 03:26 PM
Hi,
There seems to be pin for "Fuel consumption display" in LH box. Has anyone studied about this pin? Is it possible to install fuel consumption gaude to W124.036?

While many will argue that "anything is possible", it wouldn't be practical in my opinion, as it would essentially involve retrofitting the trip computer along with all of the other necessary changes to the gauge clusters, center console paneling, etc...

Efraim
12-08-2015, 03:01 AM
I don’t mean trip computer but analog MPG or l/100km gauge that is on top of w140/w129 instrument cluster. (see http://www.mbcluster.com/Services_Mileage/W140%20Rev1%20Front.jpg (http://I don’t mean trip computer but analog mpg (l/100km) gauge that is on top of w140/w129 instrument cluster. (see http://www.mbcluster.com/Services_Mileage/W140%20Rev1%20Front.jpg) In workshop manual of w140/129 there is test step of mpg gauge asking to check fuel consumption signal from LH control module that should generate pulses from 25Hz to 100Hz depending on fuel consumption (ie. 25Hz = 5l/h, 100Hz = 20l/h). So, that signal should be there in our .036 cars, only wiring from box is missing. In addition the speed gauge of .036 is electrical, meaning there might be almost all components available for the mpg gauge.  I agree that it doesn’t make sense to retrofit the trip computer nor mpg gauge for w124. At least I won’t ruin my car with these modifications. This more like theoretical thinking keeping brains ‘lubricated’ and meanwhile learning new about MB tech.))

In workshop manual of w140/129 there is test step of mpg gauge asking to check fuel consumption signal from LH control module that should generate pulses from 25Hz to 100Hz depending on fuel consumption (ie. 25Hz = 5l/h, 100Hz = 20l/h). Since the boxes are identical that signal should be there in our .036 cars, only wiring from box is missing. In addition the speed gauge of .036 is electrical, meaning there might be almost all components available for the mpg gauge.

I agree that it doesn’t make sense to retrofit the trip computer nor mpg gauge for w124. At least I won’t ruin my car with these modifications. This is my curiosity and meanwhile learning new about MB tech. :)