highwayman

O2 Sensor bank 1, pre-cat, no activity. What's up with that? I can still see voltage changes in monitor mode of the scanner. Is there a way to check the O2 sensor and confirm whether it's bad before I replace it? Thanks. MJD

Ralls

iTrader: (32)

You can have voltage osculation and still have a problem with the o2 sensor. You need to look at what the signal voltage actually is. The o2 sensor can be "lazy" and hang around 0.5 volts. A good o2 sensor will fluctuate around 0.2v-0.8v. What kind of readings are you getting?

highwayman

It will usually be between 200-800mv while driving. I've watched the voltage fluctuation and it looked like it was within spec. At idle, like you'd be sitting at a red light, is usually when the code sets. The readings at idle are typically between 300-500mv. Could that be an O2 problem or is something else generating or interpreting that data wrong? I know nothing about O2 sensors so any help is appreciated. I'll see if I can get a capture graph and post it up here so you can see the voltage fluctuation as I see it. MJD

highwayman

Okay, I was able to obtain a graph of the Bank 1, sensor 1 data while driving, engine at normal operating temp. etc. The scan was taken with an AutoXray EZ-Link scanner, data points were 3 seconds apart. The MIL light was on, although no trouble codes were found. Yeah, I know, that's odd. If you have EZ-PC I can send you the entire file so you can see exactly what everything was doing, not just the O2. I'll get a chart of the vehicle at idle later today. Let me know if you require more information and it will be posted right away. MJD

Ralls

iTrader: (32)

Your definitely on the right track. At least your diagnosing it instead of throwing parts on it until it's fixed like some people. I don't have that scanner so all I can see are the pictures you post. That o2 sensor looks healthy at cruising speed. Although I don't know how many fluctuations are supposed to occur in a 3 second span. Match that up with the Bank 2 and see if they are similar. But from what you said already, 300-500mv at idle isn't that good. I can see how that would trip a code if it lingered that low for too long.
And just a FYI, it's quite common for o2 sensors to go bad in these cars. Chances are it's bad, but a little more diagnosing wouldn't hurt.

highwayman

Well everybody, I think we found the problem. This is the graph of the vehicle at idle. The code just tripped so I started the scan. I was stopped at a light when I did the scan. At the very end the light turned green so I had to go. That explains the sharp rise at the end.


It looks like the O2 is bad, but could something else be causing the readings? I have long-tube Pacesetter headers, off-road Y, no cats, no rear O2's (codes removed), PCMforless tune, and many mods to the top end. What do you think, bad O2, or mods causing the readings? I also read it's possible for the code to throw if you have a leak in the exhaust system. I will check that next. MJD

Ralls

iTrader: (32)

Nah that o2 is dead. Even if you have work done to the motor, the o2 will still fluctuate. It's true that an exhaust leak at the flange or collector will draw in un-metered air, but I'm assuming you don't have one. If there are no blatantly obvious exhaust leaks, then the o2 is shot. Be sure to get an AC Delco o2 sensor. Any other brand, such as Bosch, have been known to fail very quickly on these cars.

koolaid_kid

iTrader: (21)

I agree, mine oscillates even at idle. It looks like your scanner is seeing the same thing the PCM is seeing, since a code was set while you were scanning.
I have heard the same thing about the Bosch, although I have no personal experience with them.

highwayman

Alrighty, looks like I need to replace the O2. I'm very familiar with Bosch (and sometimes NGK) being lousy. My dad replaced the O2's in his Ford with Bosch and they died in less than 30 days.
Where is a good place to get the AC Delco O2's? Prefer not to pay $75 for one. I will also need a connector extension since I have longtubes. I don't want to cut and splice wires into a new O2 sensor, that just seems wrong. MJD