Bad O2 sensors...?

**Motocycleguy** · 04-12-2007 12:11 AM

<div class='quotetop'>QUOTE(DamnYankee @ Apr 10 2007, 08:50 PM) [snapback]89463[/snapback]</div>

yessir...I mean they weren't even registering. Sometimes BARELY. Other times they would spike a little and then go back down to virtually nothing.

I'm needing some input guys - I don't have a clue what the problem might be. Maybe I should have Allen send me a tune with them deleted? Is that an option?
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No that is not an option... You would just kill the code and not correct your fueling problem. If your going to go that route, Delete the 02's and have allen tune you in open loop. Thats the quick easy proven fix.

I kinda suspected this if you read my first post in your "I quite!" thread. I see it in about every 10 trucks and the fix can be a real bitch in the trucks that do it! Part of the problem is the headers and having a cam dont help either. Basicaly with your headers, The 02's have moved farther downstream and the switch points have changed. Also stockers are very temp dependant. Installing some Bosch 13111's and ajusting some things in the tune can help as well, But I have a few trucks that the only fix was to go open loop. Get some data at the track I guarantee this is your issue. I bet there either flat lining or switching slowly at WOT. Most trucks that have this problem once fixed pick up about .4 at the track.

**DamnYankee** · 04-12-2007 07:07 AM

<div class='quotetop'>QUOTE(RedHeartbeat @ Apr 11 2007, 11:08 PM) [snapback]89648[/snapback]</div>

So what was the outcome? I found my issue that had been throwing codes in my truck tonight. The culprit was bad wiring from the PCM to the water temp sender. Get this, the PCM was telling me that the problem was the TPS. Tonight I started it up and it said hi voltage reading in the water temp sender. She purrs like a kitten with the new wires.

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Define 'bad wiring' Greg...?

As far as mine...Dustin hooked up his HP Tuners and pretty much had the same outcome as when Virgil checked it - low voltage on all four 02 sensors and the timing is pretty messed up (around 19 degrees I believe it was).

I still don't know where to go with the sensors and haven't had time to check the wiring or anything. And other than something real obvious, like a broken or burnt wire, I'm not sure what to look for anyway.

I'm going to have to jump ship on tuning and get a PCM and have Dustin tune it. I can't drive 5 hours to San Antonio every time I need a live tune and I'm needing a live tune. So for the time being, I'll have Dustin throw a tune on it and go from there.

<div class='quotetop'>QUOTE(Motocycleguy @ Apr 12 2007, 12:11 AM) [snapback]89657[/snapback]</div>

No that is not an option... You would just kill the code and not correct your fueling problem. If your going to go that route, Delete the 02's and have allen tune you in open loop. Thats the quick easy proven fix.

I kinda suspected this if you read my first post in your "I quite!" thread. I see it in about every 10 trucks and the fix can be a real bitch in the trucks that do it! Part of the problem is the headers and having a cam dont help either. Basicaly with your headers, The 02's have moved farther downstream and the switch points have changed. Also stockers are very temp dependant. Installing some Bosch 13111's and ajusting some things in the tune can help as well, But I have a few trucks that the only fix was to go open loop. Get some data at the track I guarantee this is your issue. I bet there either flat lining or switching slowly at WOT. Most trucks that have this problem once fixed pick up about .4 at the track.
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I guess we'll have to try the open loop route. I'm going to try to get a PCM today and make it out to TRT tonight for the tune. So we'll see what happens. Thanks for the info Moto...

**RedHeartbeat** · 04-12-2007 08:42 AM

The water temp wiring runs right next to a spark plug wire. Either it had a bad spark plug wire that was shooting spark plug fire into the water temp wiring or the wires running from the sensor to the PCM had a break in it somewhere. It's supposed to be 5 volts and it was recieving more than that from somewhere. I replaced the spark plug wire and the coolant temp wiring from an old harness I have laying around here.

If all four of your sensors are reading low voltage you've got some real issues, not bad sensors. You'd either have to have a bad fuse, corroded or loose connections or a bad ground. First, I'd check all the fuses, then check the grounds on the back of the engine block to see if they're tight and there are no broken leads. When you have SES codes active in the PCM due to the O2 readings being off, the PCM program is going to run in "SAFE" mode and your timing will be messed up until you fix the underlying issue with the O2s.

**DamnYankee** · 04-12-2007 08:49 AM

<div class='quotetop'>QUOTE(RedHeartbeat @ Apr 12 2007, 08:42 AM) [snapback]89670[/snapback]</div>

The water temp wiring runs right next to a spark plug wire. Either it had a bad spark plug wire that was shooting spark plug fire into the water temp wiring or the wires running from the sensor to the PCM had a break in it somewhere. It's supposed to be 5 volts and it was recieving more than that from somewhere. I replaced the spark plug wire and the coolant temp wiring from an old harness I have laying around here.

If all four of your sensors are reading low voltage you've got some real issues, not bad sensors. You'd either have to have a bad fuse, corroded or loose connections or a bad ground. First, I'd check all the fuses, then check the grounds on the back of the engine block to see if they're tight and there are no broken leads. When you have SES codes active in the PCM due to the O2 readings being off, the PCM program is going to run in "SAFE" mode and your timing will be messed up until you fix the underlying issue with the O2s.
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Well I lack both patience and knowledge when it comes to electrical/amps/volts etc., so if that's my issue, someone else is going to have to find it.

If it was a bad fuse, wouldn't the sensors not register anything??

And that's interesting about the 'safe mode'. So the tune might be fine, I just need to figure this O2 thing out...

**RedHeartbeat** · 04-12-2007 09:03 AM

Any time that you have an SES code showing that affects driveability the PCM runs in "SAFE" mode programming. It pulls timing, fattens up the fuel mixture, sometimes harshens the transmission shifting....

Find the 02 power source problem and you'll fix the PCM. I don't have a wiring diagram or owner's manual from a NBS truck around here right now or I'd tell you which fuse powers the sensors. If I were working on it, first thing I would check is for 12V at the sensors. I'd do a continuity check for the sensor wiring to ground. Within the O2 sensor connecter, there are two wires to check. The pink wire should have 12v to it and the black wire should be a dead short/connection to ground. Check fuses and grounds.

You could start by just removing the reinstalling the the PCM connections.

**txarkitekt** · 04-12-2007 09:03 AM

<div class='quotetop'>QUOTE(DamnYankee @ Apr 12 2007, 08:49 AM) [snapback]89674[/snapback]</div>

Well I lack both patience and knowledge when it comes to electrical/amps/volts etc., so if that's my issue, someone else is going to have to find it.

If it was a bad fuse, wouldn't the sensors not register anything??

And that's interesting about the 'safe mode'. So the tune might be fine, I just need to figure this O2 thing out...
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From what it sounds like, you just need to skip all the BS and just go to the open loop thing...

**DamnYankee** · 04-12-2007 09:12 AM

<div class='quotetop'>QUOTE(RedHeartbeat @ Apr 12 2007, 09:03 AM) [snapback]89680[/snapback]</div>

Any time that you have an SES code showing that affects driveability the PCM runs in "SAFE" mode programming. It pulls timing, fattens up the fuel mixture, sometimes harshens the transmission shifting....

Find the 02 power source problem and you'll fix the PCM. I don't have a wiring diagram or owner's manual from a NBS truck around here right now or I'd tell you which fuse powers the sensors. If I were working on it, first thing I would check is for 12V at the sensors. I'd do a continuity check for the sensor wiring to ground. Within the O2 sensor connecter, there are two wires to check. The pink wire should have 12v to it and the black wire should be a dead short/connection to ground. Check fuses and grounds.

You could start by just removing the reinstalling the the PCM connections.
[/b]

Thanks Greg. The PCM was removed and reinstalled yesterday, so everything should be fine with that. It has to be a wiring issue or something since all 4 are acting up. It's too coincidental to be something else (I would think). I'll look at it on my lunch, and if I don't see anything real noticeable, I'll get it to TRT or Prostreet ASAP and see if they can find the problem.

<div class='quotetop'>QUOTE(txarkitekt @ Apr 12 2007, 09:03 AM) [snapback]89681[/snapback]</div>

From what it sounds like, you just need to skip all the BS and just go to the open loop thing...
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Yeah, if there's an underlying problem, I want to know what it is though. I don't want to worry about something else being affected or whatever down the road.

**RedHeartbeat** · 04-12-2007 09:13 AM

The PCM does nothing with the voltage other than read it. The supply source of the voltage is totally seperate from the PCM, so the tune is not your issue.

**DamnYankee** · 04-12-2007 12:38 PM

Well, I crawled underneath and all the wiring at the sensors looks fine. Nothing is touching the headers, etc.

There was mention on LS1tech about the knock sensors being corroded from water or whatever and that fouling the sensors. I guess checking that requires pulling the intake manifold, correct?

**RedHeartbeat** · 04-12-2007 03:05 PM

Do you frequently wash your engine? That's about the only way water can get into the area of the knock sensors.

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