Man! Why Again!?
10-20-2003, 11:57 PM
#4
Guest
Posts: n/a
Don't you hate it when people just laugh at your troubles. I have included the Diagnostic prodecure for your problem. This should give you some lead to start solving your problem.
Now, if you are using a CEL fix, this doc will not help. Typically a CEL fix is done with a resistor as someone mention above. I don't know yet as to how many volts is across the resistor (however OBD-II states a rang of 3v - 40v) that you are using. But if you choose a small resistor i.e. 1/4 watt or too small of resistance. Then the resistor will fail, by either burning out resulting in an open circuit, yielding a High-Voltage fault or too small of a resistance makeing the ECU see a short circuit yielding a low-voltage fault.
If you can find clear information on where the ECU expect the voltage across this sensor to be normal then you can chose a correct resistor using ohm's law v=iR. If you cannot find such info, get youself a potientometer from radioshack or fry's then play with the resistance. Whatever you do, DONOT drive around with this test stuff. Good luck
P.S. Damn I can't include the pdf I want to send you, give me you e-mail
Now, if you are using a CEL fix, this doc will not help. Typically a CEL fix is done with a resistor as someone mention above. I don't know yet as to how many volts is across the resistor (however OBD-II states a rang of 3v - 40v) that you are using. But if you choose a small resistor i.e. 1/4 watt or too small of resistance. Then the resistor will fail, by either burning out resulting in an open circuit, yielding a High-Voltage fault or too small of a resistance makeing the ECU see a short circuit yielding a low-voltage fault.
If you can find clear information on where the ECU expect the voltage across this sensor to be normal then you can chose a correct resistor using ohm's law v=iR. If you cannot find such info, get youself a potientometer from radioshack or fry's then play with the resistance. Whatever you do, DONOT drive around with this test stuff. Good luck
P.S. Damn I can't include the pdf I want to send you, give me you e-mail
10-21-2003, 06:57 AM
#7
Registered User
Join Date: Feb 2003
Location: Buffalo NY :(
Posts: 30
Car Info: 2003 Subaru Impreza WRX
Well, I have to assume that you have some sort of aftermarket exhaust. Correct me if I am wrong, but the CEL you are throwing is a "catalytic efficiency" code, which just says that you are poluting the environment a bit, or in other words, your cat is not working as well as expected.
My understanding is that the front O2 sensor is used to measure the oxygen present in the exhaust, which is a direct measure of how lean/rich your engine is running in real time. The second O2 sensor is used to determine how much O2 is present after the cat, in other words, it measures how much is used in the catalytic converson of various chemicals into their respective oxides. blah, blah... This is done real time as your computer measures the voltage difference between both sensors. If the voltage is shown to be to HIGH at the rear sensor vs. the front, the computer thinks that the cat is broken, and throws a code. The quick fix it to fool the computer by wiring a resistor in line to the second sensor, which will always show a voltage drop when the two voltages are measured.
So, how does this apply to your situation? Well, first I must assume that your vehicle is running normally, just that you have a bastard CEL bugging you all the time. This said, I would assume that either your resister is not dropping the voltage enough. Why, I have no idea. Simple solutions include buying another (im sure there are tons of people that could sell you one cheep that will work), or just put up with the CEL and cuss a bit. I choose method two. I love my subaru, but as a former RS owner and a current WRX owner, Ive found that if you so much as stare of your exhaust the wrong way, you'l get a damn CEL. I have also found that the CEL (we) are getting does nothing to ruin your performance, so Ive learned to ignore it.
Good luck!
My understanding is that the front O2 sensor is used to measure the oxygen present in the exhaust, which is a direct measure of how lean/rich your engine is running in real time. The second O2 sensor is used to determine how much O2 is present after the cat, in other words, it measures how much is used in the catalytic converson of various chemicals into their respective oxides. blah, blah... This is done real time as your computer measures the voltage difference between both sensors. If the voltage is shown to be to HIGH at the rear sensor vs. the front, the computer thinks that the cat is broken, and throws a code. The quick fix it to fool the computer by wiring a resistor in line to the second sensor, which will always show a voltage drop when the two voltages are measured.
So, how does this apply to your situation? Well, first I must assume that your vehicle is running normally, just that you have a bastard CEL bugging you all the time. This said, I would assume that either your resister is not dropping the voltage enough. Why, I have no idea. Simple solutions include buying another (im sure there are tons of people that could sell you one cheep that will work), or just put up with the CEL and cuss a bit. I choose method two. I love my subaru, but as a former RS owner and a current WRX owner, Ive found that if you so much as stare of your exhaust the wrong way, you'l get a damn CEL. I have also found that the CEL (we) are getting does nothing to ruin your performance, so Ive learned to ignore it.
Good luck!
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