CAT3

iTrader: (9)

Trying to put together a trouble shooting page for quik reference and need to kow what mv will be shown on bad O2's. I thought it was a constant 450, but that would be odd since it is the same as O2 Simms read. Constant I can accept, but not that # or is it?
TIA, Charlie.

JWRENCH

A healthy one will bounce around the full range of the scale constantly and a bad one will stay right around the center of the scale and act very sluggish. Usually acompanied by codes P0133,134 bank 1, and P0153,154 bank 2.

CAT3

iTrader: (9)

Thats what I thought kinda, but was thinking there was a definate no-******* hey this is a bad sensor mv reading! Just curious. Thanks.

Charlie.

eallanboggs

iTrader: (1)

You should study basic OBDII. You going to have to learn this stuff so it might as well be sooner rather than later. Do you mean by your question that the O2 sensor is defective or that it is reading values that make it appear to be bad because your running too rich or too lean. Maybe your O2 sensor is good and you have a vacuum. The PCM starts adding fuel to make up for the lean condition, but it doesn't seem to be helping so the PCM adds more fuel and more fuel until a DTC gets set. Look at the O2 outputs on a scan tool. The value is going to oscillate above and below 0.450mV. It could go as low as 0.1mV and as high as 0.9mV and back again 3 times a second. It should keep doing this over and over again. That's the pre-cat O2. Then the post-cat O2 looks the same as the pre-cat O2, but with a much reduced amplitude. That is if everything is working properly. Of course you don't want to know how this stuff looks when it is working properly or you wouldn't call it troubleshooting would you? The O2 simms do NOT output a CONSTANT as you say. If you don't believe it look at the O2 Simm output on AutoTap. It's a square wave. It cycles from about 0.435mV to 0.735mV. Check it out for yourself sometime.

EFILive

iTrader: (2)

I think you mean 0.450V (not 0.450mV)

Paul

CAT3

iTrader: (9)

eallanboggs-any sugggested reading material?

Also, I am monitoring the O2 output via a Predator, and the O2 simms show a constant 450 or 455mv. something like that. Maybe these are bad, they have been on a few cars!

I got the Pre O2's bouncing everywhere along the range until WOT, when they nail 930 (B1) and 935(B2) sometimes 940/950, weather maybe ??

The higher the # is richer correct?

eallanboggs

iTrader: (1)

Paul is right. I put milli behind a value that was ALREADY expressed in milli volts. It should be 450mV or 0,450VDC Your values are going to go up like you said when you go to WOT. That's called PE mode when you leave closed loop. Normally your in closed loop after your engine warms up. The PCM is using the pre-cat O2s to set your STFTs, but when you put the pedal to the metal you leave closed loop and as they say in Louisiana your injectors "Let the good times roll". Screw the EPA and their 14.7:1 A/F, let's go RICH and makes this thing FLY! If your O2 Simms are stuck on ANY volue regardless if it is 450mV or not you have a problem. You should be setting a DTC for INSUFFICIENT ACTIVITY. That means not enough switching above and below 450mV. It should switch at least 3 times per second. It could also stay above or below 450mV all the time. That would be a different fault code, but still shows a problem with the post-cat O2s (O2 Simms in this case) or maybe you actually do have a defective catalytic converter of all things, God forbid. In your case your cats are probable gutted so it has to be the O2 Simms. Higher numbers are richer. You numbers look OK at WOT. Go to Amazon and do a search for OBDII. They have some books on it. I came up with at way of explaining LTFTs and STFTs that uses that guy climing the mountain on the game show THE PRICE IS RIGHT to illustrate how it works. If you think of the value the price is allowed to be within as the guy climbs the mountain as your LTFTs (a RANGE of 10 points) and the EXACT value of the price indicated by the ARROW pointing to the price points as he climbs the mountain as your STFTs you'll get a visual of how OBDII works. As the man goes up or down the mountain the 10 point range (LTFTs) moves with him. Also the exact price point as indicated by the arrow within the range(STFTs) moves too. Now if the arrow (STFTs) reaches the upper or lower limit of the 10 point range (LTFTs) the range MOVES to get the arrow back in the canter of the range again. If the 10 point range (LTFTs) ever moves all the way to their limit, either high limit or low limit AND the arrow (STFTs) continues to move in the same direction as the range a DTC will be set when the arrow hits the limit of the 10 point range and turn on your SES lite. The LTFTs and STFTs are a big part of OBDII along with the pre-cat O2s. The other sensors are important too, but not like those O2s. The post cat O2s only tell the PCM if your cats are working and if your cats are gutted that's a moot point. Does that help any?

TheDogofWar

iTrader: (2)

got EFILive? I can show you exactly what the readings look like with bad O2's look like. Well not completely bad but well on the way out.

CAT3

iTrader: (9)

eallanboggs, very creative way of explaining the whole thing. Thanks for the info also. I dont have CATs at all, just LT's and True Duals.

Do O2 Simms normally stay at one reading like mine are, 450, 455? Or do they also move around a little? Thought they would move around to avoid thrwoing a code.

And the higher the mV the richer correct?

Will be checking out some reading material real soon.

eallanboggs

iTrader: (1)

High(above 450mVC O2 values are rich and conversely below 0.450VDC is lean. OBDII can be confusing if you let it. Just think of it in terms of what the PCM does when it sees the O2 values(Pre-cat values). If the PCM says: I'm RICH then you must go LEAN (reduce injector PW). If the PCM says: I'm LEAN you must go RICH (pulse the injectors longer). As far as the O2 Simms value is concerned it an R/C circuit. It outputs a squarewave. On AutoTap or EFI Live it's a perfectly shaped squarewave with an amplitude from 435mV to 750mV. At least that's what mine are and that satisfies the condition. It must cycle above and below 450mV and somewhat follow the pre-cat value, but on a reduced scale. The valuse I mentioned above satisfy that condition. If yours are stuck on 450mVor 455mV they are defective. Check the wiring and connectors. The O2 Simms are pretty much bullet proof because they are epoxied shut so they are tamper proof, but the wiring or connector could get damaged. Why would BOTH of your O2 Simms go bad at the same time? They WOULDN'T! You need to do some basic troubleshooting to find out why and that's what you said you wanted to learn to do anyway. There's your chance.