P0420 question
10-06-2015, 06:57 PM
#1
Member
Thread Starter
P0420 question
Hi, Benz family.
On my 08GL450 P0420 engine light is coming on and off. Sometimes it stay off for a few thousand miles and then coming on and stays few days and going off, then it coming back in a few hundred miles stays on and goes off in a few miles. But it comes on on highway if it matters.
I hope it is not the cat. I want to check my O2 sensors on OBD scanner.
Who knows what Voltage readings i should get on sensors specifically on GL ?
On my 08GL450 P0420 engine light is coming on and off. Sometimes it stay off for a few thousand miles and then coming on and stays few days and going off, then it coming back in a few hundred miles stays on and goes off in a few miles. But it comes on on highway if it matters.
I hope it is not the cat. I want to check my O2 sensors on OBD scanner.
Who knows what Voltage readings i should get on sensors specifically on GL ?
10-07-2015, 07:33 PM
#2
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Mine has come on three times now - see other thread regarding this. Member "alx" thinks it actually is the catalytic converter.
I bought a set of O2 sensors, hoping that it was a sensor issue and not the cat itself, not realizing that the pre-cat ones are impossible to get to. I also bought a box end wrench and cut a notch in the end, and tried but failed to get the cat O2 sensor out. I haven't tried pb blaster or heat or blah blah blah ... I also ran some "guaranteed to pass" through the tank. I'm praying that it was a fluke, because the cat is $$$$$ to replace (and seeing how shoehorned the exhaust is in there, I can understand why).
I don't know how you'd diagnose it as being the O2 sensors and not the cat itself, short of replacing the sensors. If you can get them out, they aren't a very expensive fix.
You can get bluetooth OBD2 readers for $5-$25 nowadays. I'm selling my hardware OBD2 reader after I test out the bluetooth unit.
If the cat really is dead, I'll be sorely tempted to sell the damned thing out of state. I really don't think it's worth the $$$$$ repair.
I bought a set of O2 sensors, hoping that it was a sensor issue and not the cat itself, not realizing that the pre-cat ones are impossible to get to. I also bought a box end wrench and cut a notch in the end, and tried but failed to get the cat O2 sensor out. I haven't tried pb blaster or heat or blah blah blah ... I also ran some "guaranteed to pass" through the tank. I'm praying that it was a fluke, because the cat is $$$$$ to replace (and seeing how shoehorned the exhaust is in there, I can understand why).
I don't know how you'd diagnose it as being the O2 sensors and not the cat itself, short of replacing the sensors. If you can get them out, they aren't a very expensive fix.
You can get bluetooth OBD2 readers for $5-$25 nowadays. I'm selling my hardware OBD2 reader after I test out the bluetooth unit.
If the cat really is dead, I'll be sorely tempted to sell the damned thing out of state. I really don't think it's worth the $$$$$ repair.
10-08-2015, 04:43 PM
#3
Member
Thread Starter
Mine has come on three times now - see other thread regarding this. Member "alx" thinks it actually is the catalytic converter.
I bought a set of O2 sensors, hoping that it was a sensor issue and not the cat itself, not realizing that the pre-cat ones are impossible to get to. I also bought a box end wrench and cut a notch in the end, and tried but failed to get the cat O2 sensor out. I haven't tried pb blaster or heat or blah blah blah ... I also ran some "guaranteed to pass" through the tank. I'm praying that it was a fluke, because the cat is $$$$$ to replace (and seeing how shoehorned the exhaust is in there, I can understand why).
I don't know how you'd diagnose it as being the O2 sensors and not the cat itself, short of replacing the sensors. If you can get them out, they aren't a very expensive fix.
You can get bluetooth OBD2 readers for $5-$25 nowadays. I'm selling my hardware OBD2 reader after I test out the bluetooth unit.
If the cat really is dead, I'll be sorely tempted to sell the damned thing out of state. I really don't think it's worth the $$$$$ repair.
I bought a set of O2 sensors, hoping that it was a sensor issue and not the cat itself, not realizing that the pre-cat ones are impossible to get to. I also bought a box end wrench and cut a notch in the end, and tried but failed to get the cat O2 sensor out. I haven't tried pb blaster or heat or blah blah blah ... I also ran some "guaranteed to pass" through the tank. I'm praying that it was a fluke, because the cat is $$$$$ to replace (and seeing how shoehorned the exhaust is in there, I can understand why).
I don't know how you'd diagnose it as being the O2 sensors and not the cat itself, short of replacing the sensors. If you can get them out, they aren't a very expensive fix.
You can get bluetooth OBD2 readers for $5-$25 nowadays. I'm selling my hardware OBD2 reader after I test out the bluetooth unit.
If the cat really is dead, I'll be sorely tempted to sell the damned thing out of state. I really don't think it's worth the $$$$$ repair.
Yeah, i think this is O2 sensors not the cat, because i dont see any reason why cats might be destroyed=( I maintain it very well and put Chevron all the time.
Actually i will get bluetooth obd2 to see the voltage readings on sensors. I want to see how post cat are behaving.
PS. are you in San Diego as well?
10-08-2015, 05:11 PM
#4
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Did you get any quotes for cat price? And as i know there is two cats on Gls =)))
Yeah, i think this is O2 sensors not the cat, because i dont see any reason why cats might be destroyed=( I maintain it very well and put Chevron all the time.
Actually i will get bluetooth obd2 to see the voltage readings on sensors. I want to see how post cat are behaving.
PS. are you in San Diego as well?
Yeah, i think this is O2 sensors not the cat, because i dont see any reason why cats might be destroyed=( I maintain it very well and put Chevron all the time.
Actually i will get bluetooth obd2 to see the voltage readings on sensors. I want to see how post cat are behaving.
PS. are you in San Diego as well?
I hope you're right about the cat. However, alx is quite experienced, so I'm inclined to believe him. It wouldn't surprise me if the cataclysmic perverters were weak; Mercedes's engineering is so hit or miss, I'd believe anything.
The one thing working against me for cat lifetime is my engine burns oil. Not out of spec (a quart every 1400 miles), but more than zero. I don't know how much of a difference that would make. I thought engines had to be in pretty bad shape to actually foul the cats. Cold starts probably are harder on them, what with the engine running open loop.
I did not get a quote on replacing the cat. Almost certainly, it would be justified to replace both. If one is weak, the other can't be too far behind, and it sure looks to me like you have to lift the engine up to get the exhaust off. I've seen the parts selling used on Ebay for $500 or thereabouts. Of course, you can't install used, recertified, or aftermarket parts in California. I had a nice email exchange with a wrecking yard in Minnesota that flat out refused to ship one to me.
Yeah, I'm in SD. Small world. CV, to be exact. Shoot me a PM if you want to get together and have a good cry. Or if you want to borrow my ghetto O2 sensor wrench.
10-08-2015, 10:09 PM
#5
Member
I had Cat troubles on a work truck I had. '08 F-250 with the 5.4l engine. It fouled a plug causing a misfire and CEL but more importantly it dumped raw fuel through the Cats. This caused the catalytic converter to "melt down" inside and block exhaust flow. This happened at 60k miles.
I hope all it is only a bad sensor for your sanity's sake.
I hope all it is only a bad sensor for your sanity's sake.
10-13-2015, 07:03 PM
#6
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Ordered the "most popular" bluetooth OBD2 unit from Amazon. Might have been a defective unit, because while I could pair with it from my phone, Torque didn't recognize it. I'm trying a different one.
