Oxygen sensors FYI.....
10-05-2005, 08:37 PM
#26
Originally Posted by MarcusF
I’m an ex-wrench, and know a little something about O2 sensors. 
In an OBD II vehicle, you have one O2 sensor before and one after the cat (catalytic converter). The ECU uses two so it can tell when the cat is toast, which will be sooner rather than later with a dead O2 sensor. The ECU also uses the O2 sensors to stay in closed loop mode, which occurs at idle and/or cruise. With a dead O2 sensor your engine can’t go into closed loop mode and will remain in open loop indefinitely. If the car idles in open loop mode it will use more fuel than normal. The additional fuel may not all be burned and cause the cats to overheat, which destroys the washcoat (the internal catalyst material). Ditto at cruise.
My 2002 CLK430 uses Bosch Motronic ME 2.8 FI. Mazda use a licensed version of Bosch FI, but it’s not a Motronic system. That being the case, I don’t know how they can tell you anymore about what your FI logic will do when it encounters a dead O2 sensor than I just did. I have no idea what Volvo uses. The last Volvo I saw used a Bosch L-Jetronic system. That same Volvo would illuminate the CEL if you drained all the oil out of it and started the car. That's because it only had one CEL, and if it went on, the owner might want to know why before choosing to ignore it.
A resistance check can tell you if an O2 sensor is dead, but a faulty O2 sensor can still show resistance. Basically, it can pass the test and still be bad. I was taught the proper way to test an O2 sensor is to accelerate and decelerate the engine suddenly while checking the O2 sensor for voltage. It should produce 0.5 to 1.0 volts during acceleration and zero to 0.4 volts during deceleration. I was also taught to make sure and test the O2 sensors if the customer makes a request. That’s because if the wiring is good, and the ECU determines that the O2 sensor is not sending back a signal, then the O2 sensor is dead. Checking a dead O2 sensor allowed us to charge the additional diagnostic fee AND for having to install a new one. Don't cha just love service departments? Always ready to do whatever the customer wants.
Lastly, charging $400 for an O2 sensor is obscene. For that much money, you can buy a wide band sensor, a cheap gauge, and be able to check your air fuel ratios in real time. I don't know what you'd do with the information, but it would impress the heck out of your high performance friends.
In an OBD II vehicle, you have one O2 sensor before and one after the cat (catalytic converter). The ECU uses two so it can tell when the cat is toast, which will be sooner rather than later with a dead O2 sensor. The ECU also uses the O2 sensors to stay in closed loop mode, which occurs at idle and/or cruise. With a dead O2 sensor your engine can’t go into closed loop mode and will remain in open loop indefinitely. If the car idles in open loop mode it will use more fuel than normal. The additional fuel may not all be burned and cause the cats to overheat, which destroys the washcoat (the internal catalyst material). Ditto at cruise. My 2002 CLK430 uses Bosch Motronic ME 2.8 FI. Mazda use a licensed version of Bosch FI, but it’s not a Motronic system. That being the case, I don’t know how they can tell you anymore about what your FI logic will do when it encounters a dead O2 sensor than I just did. I have no idea what Volvo uses. The last Volvo I saw used a Bosch L-Jetronic system. That same Volvo would illuminate the CEL if you drained all the oil out of it and started the car. That's because it only had one CEL, and if it went on, the owner might want to know why before choosing to ignore it.
A resistance check can tell you if an O2 sensor is dead, but a faulty O2 sensor can still show resistance. Basically, it can pass the test and still be bad. I was taught the proper way to test an O2 sensor is to accelerate and decelerate the engine suddenly while checking the O2 sensor for voltage. It should produce 0.5 to 1.0 volts during acceleration and zero to 0.4 volts during deceleration. I was also taught to make sure and test the O2 sensors if the customer makes a request. That’s because if the wiring is good, and the ECU determines that the O2 sensor is not sending back a signal, then the O2 sensor is dead. Checking a dead O2 sensor allowed us to charge the additional diagnostic fee AND for having to install a new one. Don't cha just love service departments? Always ready to do whatever the customer wants.
Lastly, charging $400 for an O2 sensor is obscene. For that much money, you can buy a wide band sensor, a cheap gauge, and be able to check your air fuel ratios in real time. I don't know what you'd do with the information, but it would impress the heck out of your high performance friends.
If one does the volt test and it is out of range the O2 is bad; no matter what? If you knew they were bad or good you tested them which allowed added cost? I called a few shops today. They charge $90 (dealership get more) to scan the car with bad cel. The OMBII requires a cartridge for different vehicles(one for MB, one for Volvo, one for Honda); cartridge are very expensive. The earlier OMB will scan many different vehicles; old OMB sell for under $100 but will not scan OMBII. correct?
The dealership gets $175 to $295 for the differnt Os's. NAPA sells the universal w/posi-lock for $107.
10-05-2005, 10:16 PM
#27
MBWorld Fanatic!
Originally Posted by wallstreet
I suspect my Volvo is open loop as it has a bad rear O2 and has high gas consumption. The Volvo is OMBII. Is the one(Jetronic) you looked at OMB? The Mazda might be OMB with only one sensor. This might expalin why the cel goes on for any reason. The Volvo uses a #15738 universal O2 in front and rear position, The CLK430 2000 also uses the same O2 #15738 in all four postions. I believe the CLK430 2001-03 uses a diffent universal O2.
If one does the volt test and it is out of range the O2 is bad; no matter what? If you knew they were bad or good you tested them which allowed added cost? I called a few shops today. They charge $90 (dealership get more) to scan the car with bad cel. The OMBII requires a cartridge for different vehicles(one for MB, one for Volvo, one for Honda); cartridge are very expensive. The earlier OMB will scan many different vehicles; old OMB sell for under $100 but will not scan OMBII. correct?
The dealership gets $175 to $295 for the differnt Os's. NAPA sells the universal w/posi-lock for $107.
If one does the volt test and it is out of range the O2 is bad; no matter what? If you knew they were bad or good you tested them which allowed added cost? I called a few shops today. They charge $90 (dealership get more) to scan the car with bad cel. The OMBII requires a cartridge for different vehicles(one for MB, one for Volvo, one for Honda); cartridge are very expensive. The earlier OMB will scan many different vehicles; old OMB sell for under $100 but will not scan OMBII. correct?
The dealership gets $175 to $295 for the differnt Os's. NAPA sells the universal w/posi-lock for $107.
How's that for cheap guff?
10-05-2005, 10:55 PM
#28
MBWorld Fanatic!
Originally Posted by nopepper
im a rookie, when can you tell your sensors are bad?
Originally Posted by wallstreet
Is the one(Jetronic) you looked at OMB? The Mazda might be OMB with only one sensor. This might expalin why the cel goes on for any reason.
Originally Posted by wallstreet
If one does the volt test and it is out of range the O2 is bad; no matter what?
10-06-2005, 01:15 PM
#29
Originally Posted by E55AMG99
If you just want the codes, try other auto parts stores like Kragen, Checker, etc. as many will do this for free.
How's that for cheap guff?
How's that for cheap guff?
BTW: a hardware store in town is selling guff by the wheel barrow. You might contact them if they run out. I'll keep you in mind thanx again
