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  #16  
Old 07-09-2005, 05:56 PM
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I agree that a simple gauge did the job and I prefer them .. I have a mechanical gauge on my 250SL and it is great..NO electronics or sensors... but , along came 1996 and OBD11 code monitoring mandates .. and 4 of those codes monitor oil pressure system, gauge, and sensor circuit. So , the
existing sensor circuitry got modified to handle these new tech electronics.
OBD11 Codes Po520, 0521, 0522, o523 are all oil pressure/sensor system diagnostic feeback to ECU system monitoring, looking for faults.
If one scans the system, these faults monitor sw circuit, system voltages ,both high/low, and sensor/gauge range through the processor and tat will tell you if the sensor circuit is in range. [ but , the comparison test with a mechanical gauge is best]

It ain't a Benz thing , even Toyota has it...

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  #17  
Old 07-09-2005, 07:51 PM
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Funny you mention the OBD II code thing... Had the car throw me a P0173 (fuel trim malfunction, left bank) the other day. Per the advice of my indy mech, I tightened the gas cap and reset the code. Seems this is a pretty common code. It's been two weeks and 500 miles and no return code...yet.
But I digress. I have not experenced any other codes what so ever, pending or otherwise. I kina wish it would throw a code- at least that way I'd know.
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  #18  
Old 07-09-2005, 09:08 PM
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I would think a bad sensor circuit would bring up one of the Oil pressure circuit codes I mentioned , too... That is why I am inclined to think you do not have a problem. I wish I could find a pressure/resistance chart so you could just ohm the thing out , but I looked through all my manuals and Benz does not give that chart and their test in the CD is to hook up a mechanical gauge for verification
Do you ever see a dip in pressure at idle on a hot day and high coolant temps ??
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  #19  
Old 07-09-2005, 09:27 PM
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Arthur,
I really appreciate all the legwork you've done for me! The gauge w/ the old sender used to work intermittently-very intermittently. When it did work it seemed to indicate normal oil pressure- that is an 85 degree engine would register about 1.5 bar at idle and raise to full upon normal acceleration and then settle down to about 2.5 bar or so at 45-50 mph. I never observed the gauge fail, rather it seemed to either work or simply peg full on start up. As time and milage marched on, the gauge would work less and less often until now it hasn't worked for some time now. I just assumed it was an internal failure of the rheostat in the sender.
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Last edited by pchansen; 07-09-2005 at 09:36 PM.
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  #20  
Old 07-09-2005, 09:42 PM
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Ok, I see..

I was planning on taking an ohm reading on one of the cars here tomorrow
at a 2.5 reading and see what the sensors says .. That way, you could sub. a resistor of that value to see if the gauge responds correctly. I do this with temp senders [ I have a set value for 80C] and it tells if gauge or sender are at fault. Benz has a temp/ohms chart for those.
I have to wait til the pressure reads off pegged cuz pegged can be anywhere above 3 bar.
We are on the leading side of a hurricane here at present, so I will see how it goes in the morning [ if I still have power/cable]
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  #21  
Old 07-09-2005, 10:55 PM
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Thanks again Arthur,
I'll keep tabs and see what you come up with- First things firs though- Protect yourself from Dennis!
Good Luck
Paul
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  #22  
Old 07-09-2005, 11:10 PM
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Quote:
Originally Posted by Arthur Dalton
OBD11 Codes Po520, 0521, 0522, o523 are all oil pressure/sensor system diagnostic feeback to ECU system monitoring, looking for faults.
If one scans the system, these faults monitor sw circuit, system voltages ,both high/low, and sensor/gauge range through the processor and tat will tell you if the sensor circuit is in range. [ but , the comparison test with a mechanical gauge is best]
For what it's worth I checked ALLDATADIY.com and the above codes are not listed for my 97 S500. The list stops at P0509 and starts up again at P0561.
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  #23  
Old 07-09-2005, 11:24 PM
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I wonder if that is b/c you have the single wire sensor.. the 2 wire sensor is the 140 chassis with the chip for code monitoring. That could be why you have no codes for oil P ... That is what is throwing me ... if you have a bad OP circuit [ which we know you do] , I would expect the Diagnostic mod to pick that right up, for sure .
Let me look at mine again.

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