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Hi, I am new to this forum and have a question from the experienced members. How many O2 sensors does a 1998 CLK320 have? I am getting a P0170 & P0173 codes at the same time and have been advised by various forum members that if both the codes are triggered at the same time then the chances are most likely it is the MAF sensor. Though my MAF is as clean as a new one, it could be faulty. I have ordered a new MAF but if that doesn't fix the problem, I will try to see if the O2 sensors can solve the problem. I can only see two O2 sensors on the right side. One is visible from the top and the other from underneath the car. Would any of you help me out here. Am trying to get the parts and replace them myself. Thank you.
Last edited by sasaqlain; Dec 6, 2015 at 12:43 PM.
You've got four O2 sensors. If they're the original parts, there is a good chance they've reached the point of no return. They're normal wear parts and easily seen from underneath. Here's some info on when I did mine. . . . . . . a couple of times - www.fitzhughmedia.com/MBF/o2univ.html
Thank you for replying to my post. I will try to jack it up higher and hopefully be able to locate them, now that you have confirmed there are four sensors. The reason I am still not sure whether it is the O2 sensors that is triggering the MIL, is because the car, despite being a 1998, still has 50,000 miles on it. Also, I reset the codes and the MIL came back on, while the OBD2 was still showing 02 sensors as not ready. Hope you can throw some more light on my diagnosis. Surprisingly there isn't much available online on the CLK320 O2 replacement. I did see some signs of oil leak around the area, where the fuel filter is located. To me it seems that in my case it is a "trial and error" situation and will be very costly to get to the problem.
The O2 sensors for a 320/430/55 are all in the same spots - upstream and downstream of the primary cats. A 170 and 173 usually points to one of two things; a bad MAF or worn out O2 sensors. Since O2 sensors are a normal wear part, I'd start with them. That doesn't mean I'm right, it's just where I'd start. O2 sensors go dead on people's cars all the time. The problem is, they do it so slowly that most people never notice. Those pictures you see of 430s getting great fuel economy over long distances are cars with working O2 sensors. Dead ones won't get 28+ MPG because they're always supplying low voltage signals to the ECU.
Thank you MarcusF. I am waiting for the new Bosch MAF to arrive and will update if I see any improvement. If that doesn't solve the problem, I'll work on the O2 sensors and see if I can fix it
One quick question. Since you pointed out that the O2 sensors are pretty much in the same location, would it be possible to reach,
them, especially the wiring for unplugging. I am desperately trying to sort out the Check Engine issue as my registration and Inspection are both due in January.
I reached my O2 sensors. I highly recommend an O2 sensor socket, but other than that, there's nothing to it.
All four O2 sensor wiring plugs go into a four port socket under the car near the front of the passenger side door. With ME 2.8, each O2 sensor has a unique plug and cannot be plugged into the wrong port. You have ME 2.0 and I don’t know whether your plugs are unique or not. You may want to pay close attention to which port each plug goes in to.
If the car is run without the O2 sensors plugged in, the first time it goes into closed loop mode (which is at idle or cruise) the CE light will illuminate and P0134, P0140, P0154, and P0160 error codes should all be registered.
Just to update my situation in order to help those that may have a similar situation. Somebody, on one of the forums had suggested that if both the codes (p0170 & p0173) show up at the same time, then most likely it's a faulty MAF. I drove the car with a check engine light all year long and fearing my trial and error repair work might cost me thousands of dollars to fix. Anyways, I took the leap and ordered a Bosch MAF. After replacing it and reseting the codes, I was relieved to find out that, that fixed the issue. I was able to pass the NY state emissions inspection and renew my registration.
Last edited by sasaqlain; Dec 17, 2015 at 06:57 PM.
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