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Bosch Fault Code Table; Stored fault % from diagnostic socket.
Topic Started: Wed May 2, 2007 7:14 pm (20,615 Views)
nickaliath
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Bodywork Specialist
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This is for anyone who is having troubles with engine running.

Ideally you need an automotive multimeter with dwell setting on it, to read off the % given from the ECU.

- You will need to unscrew the cap off the round diagnostic socket.

- You will then see a number of connecting holes.

- You will need to connect the multimeter to hole 3 and earth the other wire from the multimeter on the vehicle body.

- With the engine running at idle you should get a reading.

- If there is no fault you should get a reading which fluctuates 50 (+10 or -10)

- If there is a fault you will get a reading which stays the same and does not change.

- Now see the tables below.

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Matt
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Another great entry Nick ;)

Pinned.
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nickaliath
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why thank you kind sir :)

it certainly worked for me.
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pentoman
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Am I right in suggesting that this is only available on cars with an O2 sensor?
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nickaliath
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i dont think so. if you look at the list above in the table it states specifically for the lambda only readings.
the other measurements are for both.
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pentoman
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How have we got by for so long without this information! Many, many thanks for posting Nick.

I just tested my car tonight. Showed 50% duty cycle so no problem (it's non-catalyst). Just to test it I unplugged the coolant temp sensor with the engine running and it jumped straight to 70% as expected ;). I also went for a 2 minute drive with a portable meter to see if anything came up (I'm not sure if you need to?) but it didn't.

You can test this with a voltmeter as well. You have to be more cunning to calculate the percentage. The sums to do are:

Voltage / Max voltage
then 1 - (Voltage / Max voltage)
then times that by x100

(you need to measure max battery voltage with engine running, but it will be 13V ish)

You end up with a percentage, then refer to the above table.

Or if you can't be bothered, take it from my readings that 6.6V (between pins 3 and 2) was equivalent to 50%.
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Brum-brum2
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Great information, unfortunately I've fallen at the first hurdle : can anyone tell me th erough location of the ECU on a 1991 2.0 4 door saloon?

Cheers.
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Conrad
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Behind the battery. Take out the plastic cover.
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pentoman
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Brum-brum2
Sep 17 2007, 01:45 PM
Great information, unfortunately I've fallen at the first hurdle : can anyone tell me th erough location of the ECU on a 1991 2.0 4 door saloon?

Cheers.

You don't need to go near the ECU - the diagnostic socket is on the front, passenger side wing, it's black plastic and should have a plastic round cap on it.
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Brum-brum2
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pentoman
Sep 18 2007, 11:17 AM
Brum-brum2
Sep 17 2007, 01:45 PM
Great information, unfortunately I've fallen at the first hurdle : can anyone tell me th erough location of the ECU on a 1991 2.0 4 door saloon?

Cheers.

You don't need to go near the ECU - the diagnostic socket is on the front, passenger side wing, it's black plastic and should have a plastic round cap on it.

Thanks pentoman for that and thanks to Conrad fot replying to my ECU location question.

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tom_kauf
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That's a great table. B)
I've checked my Diagnostics plug before (and it wasn't 6.6V), but now I was planning to check what it meant.

The only problem is, the Table says 90% is not assigned. I have an average of 1.1V at pin 3. It fluctuated between 0.772V and 1.288V (using the Min, Max fuction of my multimeter) with Vbat being 13.84V. So that's about 90% :blink: ?????

Hmm, strange. One day I'll take it somewhere to get diagnosed. I read somehwere to make sure the engine is in closed-loop mode (properly warmed up past 80degrees), so I did that. And I checked my O2 sensor itself (at the connector under the driver's seat) to see if it's fluctuating properly around 0.5V. And it is. But the Diagnostics output seems strange.
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pentoman
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The reading shouldn't fluctuate that much, it should be fairly steady if it is showing an error. So perhaps yours isn't an error and it's just showing the O2 value.
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tom_kauf
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Thanks pentoman, that would be good (and make more sense).
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northern_pete
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mine appears to have no pin 3!?!?!?

theres a hole but theres nothing in the hole, just plastic, all the others have a brass sleave inside!

help!!!
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northern_pete
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anyone know why?!?
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pentoman
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If there's no pin then most likely reason is you've got an earlier car without diagnostic. My '86 C reg doesn't have it...... but my 1990 does.
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Barron
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Mine's an early C Reg 86 model.

Has cold start problems. It starts, but will not idle until after a few minutes, then it idles at around 1200/1400rpms.

I've changed the air control valve, & had new injectors fitted. Having all the C02 set up next week.

Failing that, where would the experts start next???

Barron.
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pentoman
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Please start a new thread (browse to the Engine forum then click new topic or new thread) because your car does not have this diagnostic it's too old.

Sounds like the air control valve is doing nothing - try unplugging it, does the idle change?

If not then maybe OVP. If it does then could be engine temp sensor. But could be a bunch of other stuff too.
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iamjohnlarkin
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Need some help

Cannot view the fault code tables.

What am I not doing or doing wrong?

Await the inevitable ribbing.

JL
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cossie connoisseur
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there can be only one ;-)
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image needs restoring
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merc190uk
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pentoman
Tue May 20, 2008 6:36 pm
If there's no pin then most likely reason is you've got an earlier car without diagnostic. My '86 C reg doesn't have it...... but my 1990 does.
got mine upto running temps today :faint:

lifted the port lid


no pin 3 :C :C

typical

is there any other option for us poor pin 3 less guys

booking it into the garage end of month to get this sodding emmsions sorted, tried again today but when i lean it of it just runs like crap or dies :C
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pentoman
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Not that I'm aware no. They upgraded the KE system (it's KE-III on a 2.5-16) as the 190s went along. So I'm just guessing the earlier cars had an older system without fault diagnosis.
Good luck with it these things are a bummer when they don't work. That said, the KE diagnosis will only show up computer/sensor-related problems. And, as a number of us have said (and my local mercedes specialist recently confirmed) the whole engine should work fine without any of the computer side of things - its for emissions mainly as well as cold starting. So without the computer, it may stumble when cold but once warmed it should run fine without computer control. I've tried this a good few times myself. And I think I've said this before but I'll say it again - if you're serious about it you need to disconnect the KE computer and get the car running properly like that. Because otherwise it's just going to be red herrings.
Without the KE computer I'm not sure what could cause your problem - but quick list from what I've learned:
Any air leaks in the black pipes (don't worry about the small thin vacuum pipes yet) - especially check the ones going to the 4 injectors.
Fuel pressure (never checked this but my specialist will do when I can afford it)
Other pressures like differential pressure inside the fuel distributor
Err injector problems.
Not sure if it could be spark related but worth being sure (e.g. spark only strong enough to ignite a very rich mixture? Probably loads of codswallop but hey strange things happen!)
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merc190uk
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Thanks Mate all food for thought
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pentoman
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merc190uk
Mon Jan 26, 2009 7:31 pm
Thanks Mate all food for thought
Stop fannying about, get it done dear boy! You'll be buying a mondeo otherwise
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umran9
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just done this check on my 2.5-16v as my car has a misfire on idling and sometimes wont start... it gave me percentage of 44! does that mean the ecu is fine?
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Benzsc1
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According to the chart it should be fluctuating and if stuck at 44 then I am guessing and someone else here please correct me if I am wrong but it may be your air flow sensor at fault that is purely taken from the fact that a read out of 40 indicates this and given the fact you are working on percentages I imagine that you would round up or down??????

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umran9
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where is airflow sensor located?
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kentronix
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I'm only really here for the Kitchens

I figured round it to the nearest but when the one I did was reading 42% (based on voltage calculations) I then got a duty cycle meter which read out 50%. It was a car with cat so it was saying the lambda was at fault.
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bri957
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I think you are supposed to disconnect the purge valve (the one with a MOT marking) before taking a reading.

Anyone confirm?

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blackcerb
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But how can i read with an multimeter? if the battery is 13,5 the read must be 6,8 or what?
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kentronix
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I'm only really here for the Kitchens

Use the formula from pentoman's post.

100 x (1 - (Port voltage / Max battery voltage(when running)))

Its not massively accurate but given the ratio's are 10% apart it should give you a clear answer.
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NO190
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My multimeter has Dwell settings 1, 2, 4 and 6 cyl(same collor). But the Dwell is typed at button 1 not the others. But i guess Dwell must be choosen from the nummber of cylinders? Is this right?

I have no instruction manual for the multimeter so thats why im wondering.

If so my multimeter showed steady 36.2 on 4 cyl setting. And on Dwell 1 cyl it steady says 72.3. What is right?

If the 36.2 is right, it is somewhat inbetween 30 and 40 O.o im confused. (and tired) :D
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kentronix
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I'm only really here for the Kitchens

Its duty cycle, thats not the same as dwell angle is it ? Not really sure. Duty cycle is the ratio of peaks to troughs in the signal.
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NZ_190
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Hi I just tried this on my 2.6 and using your calcualtions

Max voltage is: 13.8

pin 3 fluctuated between 10.7 and 11.1 so avg is 10.9

on a standard multimetre got a 21percent which by the table means that "full load contact has incorrect polarity or is faulty, 20% readout only if decel feul shut off microswitch is activated"?????

What does this mean????? My micro switch is stuffed?? is that it? Or is there more to it? sorry for my ignorance.

Really apreciate any advise guys :)
Edited by NZ_190, Sun Oct 3, 2010 6:24 am.
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NZ_190
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bump:)
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dee2.516v
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...drifter...
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very usefull info there...
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merc190uk
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ok ive just done mine

battery at tickover = 14.2 volts
reading from pin 3 = 2.71 volts

sum 2.71 divided by 14.2 = 0.1908450704

then 1 minus 0.1908450704 = 0.801549296

this result 0.801549296 is then times 100 = 80.1549296

this i am assuming is my reading and represents 80 ?

if so i have a broken temperature sender ?
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Matt
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merc190uk
Sat Sep 17, 2011 7:20 pm


if so i have a broken temperature sender ?
Replace it then!


:P
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merc190uk
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Mmm looks like i will have to :-/

i didnt check but isnt the airflow sender joined into the loom ?

cant be, but i dont remember seeing a way of seperating it. will look in the morning. one thats done im expecting to see other codes :-/
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Matt
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merc190uk
Sat Sep 17, 2011 8:12 pm

i didnt check but isnt the airflow sender joined into the loom ?
The potentiometer plug?
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