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2001 SLK320
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Discussion Starter · #1 ·
hi all I am hoping to get some feed back for a problem with my 2001 SLK 320. One day last week the wife and I had gone for a drive in the car, whilst we where out the check engine light popped on. Once home I attached my analyzer to read the codes, To my surprise I had 2, both for the O2 sensors bank 1/1 and bank 2/1 PO130 Up Stream. I then restarted the engine and read the live dater it indicated NO voltage coming from the upstream O2 sensors, the car was in OL and the long and short term fuel trim read 0%.

I have bench tested both O2 sensors the heater circuit ohms were normal and when heated with my propane heater both came up to 0.98V which is normal.

Does anyone have the electric diagram showing the O2 sensors or any input on this matter would be great.
Thanks and stay save.
 

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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What are you using to read the Car with ?

Anything other than SDS can and does lead many folks on chasing unicorns ;)
 
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Discussion Starter · #6 ·
What are you using to read the Car with ?

Anything other than SDS can and does lead many folks on chasing unicorns ;)
Hi Dave I use an AUTEL whish i have used on the car for the passed 7 years, and it has done me well over that time. I also have a PC based Scan Master-ELM, which also indicates that neither of the O2 are not getting the voltage to the ECM and the ECM remains in OL, therefore the LONG and SHORT term fuel trims are unable to act (no input)..
Thanks for your input.
 

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Discussion Starter · #7 ·
Can anyone tell me what eeprom is in the SLK320 I think that it will be a 24 EEPROM, Microchip, but unsure what the name of it might be. I cant see and makes on the chip in my ECM or the spare one that I got. The person that is going to do the work for me wants to make a copy of my original just incase anything was to go wrong. He thinks it starts with MC24*****

Thanks
 

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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5P08
 

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Discussion Starter · #12 ·
Update, the ECM that I ordered arrived and over the weekend I had the eeprom changed from the original to this one. The unit was replaced in the car I turned the key and the car stared up, Great it work like you all said it would. Took the care for a run and within 10 to 15 minutes the check engine came on. Once back home I check it with the scanner and I have exactly the same problem as before. Not reading the upstream O2 censors and will not go into close loop. I cleared the faults and put the scanner to measure mpg and ran the car on the Queen E (motorway) on Cruise at 70 mph it indicated 32 mpg. Which is normal for this car since I have owned it. Does anyone have any idea what might be happening. In closing just let me say if the check engine light was not on I would not know there was anything wrong with this car. No misfire, No white or dark exhaust, No backfiring and NO hesitation at all.

(y)
 

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Discussion Starter · #15 ·
Well it could be but i have had them out and bench tested.. Results Drive side 9.6 ohms and using a propane touch on the tips it went to 0.943 Volts. passenger side 9.2 ohms and 0.948 Volts.
With both dropping off the volts quickly when heat removed. So I assumed they are both close to spec.
 

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Isn't Open Loop operation normal at idle and at WOT? Have you tried monitoring for Closed Loop operation when driving?
 

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Well it could be but i have had them out and bench tested.. Results Drive side 9.6 ohms and using a propane touch on the tips it went to 0.943 Volts. passenger side 9.2 ohms and 0.948 Volts.
With both dropping off the volts quickly when heat removed. So I assumed they are both close to spec.
I mean, what's left? You already replaced the ECU, which is normally the most expensive part.

You could probe the harness from the ECU to the sensors and see if it's open circuit or has corrosion (high resistance).

Usually the ECU exchange is the last resort, after all other avenues are exhausted....

....Unless it's a Chrysler. But that's a different story, Chryslers are trash. 🤣
 

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Discussion Starter · #18 ·
(y)No it came from a 2001 SLK320 I did back probe O2 wires when it was running and the O2 Sensors voltage was getting to the ECU. Usually I'm good engine wise as for electronics not so good. Right now all i can do is as you say check the wiring and sensors and hopefully track it down sooner than later,🤬
 

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Just because the voltage is getting to ECU doesn't mean it's within spec.

If you're not willing to spend money, just swap sensors from bank to bank and drive.
 

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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Isn't Open Loop operation normal at idle and at WOT?
Only WOT (AFAIK)

So I assumed they are both close to spec.
They have to be bang on spec, MB's, (as with many other marques) are very sensitive to O2 Sensors ;) ......................

So much so that I will only fit Genuine perhaps use Bosch on an older car .................

Wait until ya get involved with later Diesels that use NOx Sensors ..................... Oh wow, different ball game those 🤣
 
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