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  #16  
Old 08-31-2007, 05:52 PM
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http://www.peachparts.com/shopforum/showthread.php?t=107630&highlight=CODE+READER
Post #8 links to a PDF that list the codes for different model/years.

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1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14
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  #17  
Old 09-01-2007, 01:37 PM
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How about the coolant temp sensor ? This one sends signals to both the ICU and ECU and an intermittent disconnection of this sensor would put the car in a limp mode and restart would remove it from that mode until it happens again. So check its wiring to both the ECU and the ICU, make sure there are no loose connections or cuts in the harness. If that is fine, I would replace that sensor if it has not been replaced recently. Intermittent CPS operation is also a good possibility, but I would assume that the car would most likely stall without the CPS signal. Also hoping that there are no vaccum leaks, i.e. unmetered air entering the intake, that could cause the oxygen signal to reach limits and I am not sure what the ECU would do if it always gets a constant signal. But this you can test and see if indeed the oxygen signal is turning into a DC signal.
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  #18  
Old 09-01-2007, 06:16 PM
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Good idea. Which of the sensors are you speaking of in particular?
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  #19  
Old 09-01-2007, 07:26 PM
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I am not sure about your car but on my 87 260E, it is the last one on the engine, towards the windshield. It is a two terminal sensor. When the car is cold, the sensor's resistance should be between 2.5 and 3.5K and when the car warms up, at 80 degC, the resistance should drop to between 250 and 350 ohms. The exact values could be different but in general the resistance should drop by a factor of 8 to 10 when the temp changes from 20 to 80 degC.
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  #20  
Old 09-01-2007, 07:31 PM
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brewtoo,
If you pull the EHA plug and drive it you won't have any computer input into the fuel mi_ this includes the computer itself, the o2 sensor the coolant temp sensor... you wont have cold start assistance or emmission tuning but the car should run perfectly well this time of year without it. If it does not stall with the EHA unplugged then you know the problem is mi_ related, if it does stall with the EHA unplugged then you must look elsewhere.

(Bad ecs key on this key board thus fule mi_)
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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14
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  #21  
Old 09-01-2007, 07:38 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
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Ohm's range from the temp chart in the /Engine Manual-Combustion Manual-07.3 Mechanical/electronic gasoline injection system (KE injection)-121 Testing electrical components of KE injection system. page 60

Temperature °C........Resistance k?
-20........................15.7
-10.........................9.2
0............................5.9
10...........................3.7
20...........................2.5
30...........................1.7
40...........................1.18
50...........................0.84
60...........................0.60
70...........................0.435
80...........................0.325
90...........................0.247
Same resistance values apply to KE intake air temp sensor.
I think this chart applies to these 2 sensors for all KE systems but don't know for sure.
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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14
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  #22  
Old 09-01-2007, 08:34 PM
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Thanks for all the input guys.

I have to pause this project now and put in a new water pump. And belt tensioner. Doesn't it just figure? The joys of these old cars!
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  #23  
Old 09-06-2007, 06:27 PM
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Looks like Mr. Patel may be the winner!

Preliminary tests with the Arthur Dalton Honorary Code Reader reveal:

CIS CODE 31 - Intermittent contact in engine coolant temperature circuit.

I wonder if it is the harness, a connector or the sensor?

Is it the 4-pin sensor all the way in the back of the head? Or the single-pin in front of that? Or the 2-pin sensor in front of that?

Thanks
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  #24  
Old 09-06-2007, 06:32 PM
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Quote:
Originally Posted by brewtoo View Post
...the 4-pin sensor all the way in the back of the head...
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2640UYRR426A13Q8DX&year=1991&make=MB&model=300-E-002&category=C&part=Water+Temp.+Sensor&appEngines=_any
__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14
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  #25  
Old 09-09-2007, 09:59 PM
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OK, I have swapped that temp sensor between my two cars and deduced that the sensor is not the problem.

Could this be a ground connection problem?

Is there a document anywhere that shows all the geound connections thoughout the car? Seems like I've seen one somewhere.

The fact is though, that 4-pin connector does not use a ground connection and the temp sensor is isolated...really two identical temp sensors in one.

So, all things considered, it must be a wiring harness issue.

Agree?
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  #26  
Old 09-09-2007, 10:22 PM
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Wiring harness is possible, one set of cables should go to the ECU and the other set to the ICU, check continuity. There was one person on the forum who tried everything and it turned out to be that the coolant sensor's wire were cut somewhere due to rubbing against a metal part.
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  #27  
Old 09-10-2007, 12:24 PM
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My factory manuals only go thru 1987. Of course, by 1991 they had changed the temp sensor from a 2-pole to a 4-pole.

Where might I find the proper wiring diagram?

Thanks
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  #28  
Old 09-10-2007, 01:59 PM
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Brewtoo, I have some pictures in my CD, but the files are large to post, send me an email address. Does your car have the mechanical fuel injection system, or the hot wire/hot film system ? What is the exact engine/model number ?
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  #29  
Old 09-10-2007, 08:02 PM
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Quote:
Originally Posted by brewtoo View Post
Preliminary tests with the Arthur Dalton Honorary Code Reader reveal:

CIS CODE 31 - Intermittent contact in engine coolant temperature circuit.

OK, one source says code 31 is the coolant temp circuit. Another source says code 31 is the outside air temp circuit.

Can anyone verify which is correct?
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  #30  
Old 09-11-2007, 09:37 AM
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Heads up for anyone who may go down this road...

It would seem there is an error in this document: http://www.geocities.com/MotorCity/Downs/1039/mercedes/cs1000_mb.pdf which was referenced earlier. It is a big 169 page pdf file listing error codes...it's actually a manual that came with a code reader.

I have a CODE 31 which that document says is an intermittent coolant temp sensor circuit.

But now I notice that it says that both error code 28 AND 31 are a coolant sensor circuit problem. Obviously, that cannot be true.

The factory documentation says code 28 is a coolant sensor circuit problem, and 31 is an intake air temperature sensor circuit problem. However, there is plenty of confusion supplied in the factory documentation, too, because in the repair section they twice refer to air temp sensor as the coolant temp sensor, even though they call it by the correct part number.

So I've been chasing a coolant temp sensor circuit problem when, evidently, my problem is with the air intake temp sensor circuit.

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Last edited by brewtoo; 09-11-2007 at 09:45 AM.
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