2002 Avalanche 5.3 O! M! G!

One thing that could cause those O2 sensors to not function is a malfunctioning sensor heater. Parts aren't what they used to be... the heater in the sensor could be bad right out of the box. Don't quote me on this, but I believe those sensors have to reach about 600 DegF before they can even function.

• Use an ohm meter to check the resistance of the heater in each sensor
• Use a volt meter to check for 12v and a good Ground at each sensor
• Check for loose wires ( by jiggling them )
• Check for dirty plug / socket terminals


If worse comes to worse and all of the other tests pass, measure the current flow into the sensor heaters.


• If you have a DC amp clamp this is easy.
• If you have a DC amp meter you'll have to cut one of the supply wires and put the meter in line.
• If you only have a volt meter, you can put a low value resistor inline and measure the voltage drop ( 0.1ohms is usually about right )


If the sensor heater checks out ok, but the sensor still doesn't give any ECU values ( when fully warmed up )

• Use a volt meter or Oscope to check the signal voltage of each sensor ( at the sensor first, then at the ECU )

If you find that the sensor is not generating a proper signal:

• You might also consider doing a propane torch test with a volt meter on each of the dead sensors to verify that they actually work.

If it fails that test... you have a bad sensor

Also, although the goal here is to fix the actual vehicle... if you are just desperate to pass inspection... most states have an inspection waiver for the emissions portion of the inspection process.

The way that it usually works is that you have to take it to a professional mechanic and spend at least $300 on it trying to fix the emissions issues.
You can take the receipts from the mechanic into the DMV ( along with your safety inspection that you passed ), pay an additional DMV fee and renew your vehicle using the emissions waiver.

You'll still want to fix the actual problem though, because if you don't you'll have to spend that $300 extra buck every year!
... plus put up with all of the crappy running and engine problems

Since you are suffering from lean misfires ( engine adding lots of fuel ) [ back when your O2 sensors were actually working ].

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Edit:
I just noticed that in one of your previous posts that you posted this detailed fuel trim by bank #
Is it available by sensor #?
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• Check your scan tool detailed fuel trim information.
Don't just check the total average Short Term trim.
Check the detailed Short Term trim by Sensor #.
It should tell you how much each O2 sensor is contributing to the over all fuel trim.

This is an OBDII standard so it should be supported.
It's OBDII service 01 PID's 20 through 27

This could help you out big time!



• For example you could have an air leak in one of the exhaust manifolds
If this happens you'll see one bank primary and secondary contributing more Neg than the others.


• You could have a leak in just the exhaust pipe somewhere
If this is the case you might see that only 1 or more of the secondary O2 sensors are contributing to the Neg.


• If you see that they are all contributing evenly to the Neg... then you have a mixture problem, ECU problem or other electrical problem.
• You could also be burning coolant, which messes with and contaminates the O2 sensors
• You could also have bad or wrong fuel, this would mess with your O2 sensor readings too.

Added info: I do have a frequent misfire on #6. Compression is 135 and changed the coil and plug again. I swapped the wire with the one next to it to see if it follows... it didn't. But, since changing the fuel injectors IF that engine is going to misfire, it does it mostly on #6.

Keep in mind that B1S1 is stuck at like 472 and did throw a code P0134 for Insufficient Activity on B1S1.

At Idle: B1ST 50%, B2ST 2%, B1LT 25%, B2LT 25%
At 1500 rpm: B1ST 23%, B2ST -3%, B1LT 25%, B2LT 21%
At 2500 rpm: B1ST 52%, B2ST 1%, B1LT 11%, B2LT 21%
At 3500 rpm: B1ST 52%, B2ST 5%, B1LT 0%, B2LT 23%

Which bank contains cylinder 6?

Another afterthought:

Check for leaky EGR valves. They can really play games with your fuel trims. I just had a similar issue the other day with rough running, misfires and idle problems. The EGR was not shutting properly and sending the fuel trims ALL OVER the place!

The easiest way to check this is to do an EGR bypass as a test. Replace the EGR gasket with a piece of gasket material that has no holes in it, then bolt it back down.

If your situation improves... the EGR valve was part of the problem.
If not... well, then it wasn't. Don't drive it like that. It's a Felony

Have you rechecked your fuel pressure?
You previously had a lot of problems with fuel pumps. Are you 100% sure that this one is still working correctly?

Hey hakachukai Thanks for all the replies. I don't have time right now to read everything in detail right now but caught some things skimming through it all. On the truck the 8th digit is a "T". I didn't understand the whole thing till now but I knew the fuel pressures are different between the T and Z motors but didn't relate it to type of fuel. Z's are to have something like 28psi and the T's are 55psi in fuel pressure. The online mechanic that was helping me had said several times that minimum pressure should be 55psi but said that the present fuel pump is ok since it maxes out at 59psi. So, hopefully it is OK even though min pressure is 50 psi. I want to try fixing that somewhat of a kink I had while bending the 3/8 line before changing the fuel pump again.

I'll read everyone's comments later. I appreciate everyone's help

I have to try that EGR test you mentioned and cylinder #6 is on Bank 2. Gotta question... the O2 reading 472 is a rich condition isn't it? And close to zero is a lean condition? Or do I have that backwards? At this point with the truck... I would really like to fix it to where it runs right and not worry about detonation or MPG. I actually need it to start towing $500 cars back home to fix and sell them. Plus our son has a POS Jeep Liberty undrivable now and we're paying insurance on it still cause he lives 3 hours away. I need to get back home to take it off the road, fix it, sell it.

I did notice, on the Avalanche, when I had the gas tank down that there was a rust hole in a sub frame, what I call the subframe, that was pretty decent in size. That's a debatable fix of pass it on, get another truck type of deal. I asked around for an illegal inspect sticker and found a person but really would like to roll up and pass inspection.

I'm an old time high school mechanic. I graduated in 1980... lol. I worked on my family's cars and friends. It was all like a good time with friends doing that type of work. Never made a living at it... but in todays world and todays car I would like to start again to save money and to make it. When the vehicles started leaning more and more computerized I drifted away from it all and went to school for computers and made a living at that type of work. Well, now being disabled and at home all the time I tinker with a lot of things to keep myself busy or I'll go crazy. I can work on things but can't do it fast enough anymore to make a company money. I do kind of want to work for a local mechanic to learn a lot more but it'll mess up my disability, which sucks. If it weren't for this problem with this truck opening the door to present day mechanics I'd never realize that it's a lot similar to the type of work I used to do out in the field of automated machinery. I'm illiterate to todays Must Use tools... the scanner. I only started learning about these fuel trims and stuff and a Tech 2 scanner a couple of months ago. So I'm still learning to read the meaning behind the numbers. So please bare with me if I have a "DUH" moment from time to time. Lol. Gots to get me a good scanner, like a Snap-On Solus!

Thanks guys

ok, so at this point I'm just consolidating information and adding a few questions so that we can get all wrap our head around the facts.

Gotta question... the O2 reading 472 is a rich condition isn't it? And close to zero is a lean condition? Or do I have that backwards?

I have no idea what an O2 reading of 472 means in the context of your engine computer and scan tool.
If it means 472 millivolts, then that would be lean.

You could test it and figure it out by pulling vacuum hoses to force it lean.
Then spray some gasoline / carb cleaner in the intake to force it rich.
observe the numbers during these two tests and see what happens.

Added info: I do have a frequent misfire on #6. Compression is 135 and changed the coil and plug again. I swapped the wire with the one next to it to see if it follows... it didn't. But, since changing the fuel injectors IF that engine is going to misfire, it does it mostly on #6.

Keep in mind that B1S1 is stuck at like 472 and did throw a code P0134 for Insufficient Activity on B1S1.

At Idle: B1ST 50%, B2ST 2%, B1LT 25%, B2LT 25%
At 1500 rpm: B1ST 23%, B2ST -3%, B1LT 25%, B2LT 21%
At 2500 rpm: B1ST 52%, B2ST 1%, B1LT 11%, B2LT 21%
At 3500 rpm: B1ST 52%, B2ST 5%, B1LT 0%, B2LT 23%

Which bank contains cylinder 6?

and cylinder #6 is on Bank 2

On the truck the 8th digit is a "T"

T's are 55psi in fuel pressure

The online mechanic that was helping me had said several times that minimum pressure should be 55psi but said that the present fuel pump is ok since it maxes out at 59psi. So, hopefully it is OK even though min pressure is 50 psi.

Was the actual fuel pressure ever measured and verified?

I did notice, on the Avalanche, when I had the gas tank down that there was a rust hole in a sub frame, what I call the subframe, that was pretty decent in size. That's a debatable fix of pass it on, get another truck type of deal. I asked around for an illegal inspect sticker and found a person but really would like to roll up and pass inspection.

DON'T!!!

If you can pass a legitimate safety inspection, than that's fine... and you may well be able to do so.
If you do it illegally and that sub frame snaps, resulting in an accident that seriously injures or kills someone, both you and the inspection tech that passed it are probably going to jail!
... then there will be the lawsuits.

Not worth it! If it won't pass a safety inspection due to rust, just dump it now and walk away. The rust will only be worse next year!

Gots to get me a good scanner, like a Snap-On Solus!

Actually you don't.
Don't get me wrong, they are nice and can help you get a job done fast. They are also expensive.

You can get the same functionality for less money ( but usually more time on time job ) using cheaper tools ( but more of them ).
It's a classic case of time vs money.

You might be surprised what you can do with an $11 ELM327 OBDII module a 2 channel PicoScope and a 60A DC amp clamp.
Since the ELM327 is not bi-directional, you simply have to come up with creative ways to perform tests yourself.

Hey Hakachukai… When I meant pass it on meaning let the next guy take over where I left off. That's basically what I'm doing, picking up where the last guy left off... but inform them of it so they can have a turn at it. I'm also a welder too. I figure that I'm so close to being done with it that I could have a nice running decent 5.3 beater truck at best with comparable gas mileage to our BMW SUV. My plan was too have this Avalanche running by the end of last summer so I could take our SUV down for repairs and have it ready for most of the winter but that didn't happen. The Avalanche was also a gift to me from my daughter and is the main reason of getting the truck usable. I start talking negatively of the truck when I get frustrated. If you would look at my yard you would see that I don't let my vehicles go to easily... especially a gift. I'm not like the used car dealer down the road that sells auction cars without fixing them. What a scumbag.

I would spend the money on a used Solus like I did with this Tech 2 scanner I bought. They are about the same price, used, for either one of them. I also figured to sell the Tech 2 as well, when I'm done, since the Solus will do the Tech 2 job and more.

Yes the 472 is mV. The fuel pressure I've checked many times and yes it holds at 50 psi during idle and jumps to 59 psi WOT. Pulling the Vacuum line of the regulator holds the pressure at 59 psi.

I was going to get to the truck today but gotta put a strut in the Bimmer today instead.... Life, always something...

I checked voltage at both O2S1 connectors and had 14.3v at each. I did not check ground to ground though. Inspected each connector and connected them back together. Scanner still saying I have an open on the one O2 sensor while the other 3 were working as they should. How lucky am I to have a shorted and an open O2S1 sensors. I should've played the lotto that day.

I get back to yas when I get another O2 sensor and fix that fuel line restriction.

Thanks as always

the 02 circuit with the 472mv reading is not showing lean or rich, it is showing that the 02 is not being heated up within the allotted time. either the heating element of the 02 is bad or the 02 wiring is bad.

with the KOEO, scantool on and showing the 02 PID at 472. unplug that sensor connector at the sensor. the PID should still read 472. with a test light attached to a good known ground or battery negative, touch the signal wire on the harness side of the 02 connector. the scantool PID should read 0. if it stays at 472 you have an open in the signal wire between the PCM and the connector. If it drops to 0 your sensor is bad.

fix that sensor first, the other sensor will start working...

Hey ScannerJohn thanks for the reply. Yes I noticed that when I disconnected the new B2S1 sensor I just put in... it went to 472 as well. That B2S1 sensor that I took out was dropping to zero. So, I took that sensor that went to zero and swapped it with the B1S1 sensor thinking it was going to pull it down to zero but it's still maintaining 472 mV which is, ugg!!!, pointing to that open on the signal wire. Just to be extra sure I'm going to put the good sensor from bank 2 to bank 1 and see what happens then.

That's all I need is an open circuit. I should've bought that damn circuit tracer I saw on facebook over the summer.

This is probably useless information right now till I figure the O2 sensor problem out. But...

1) Loop never closes for the fuel trims to start working. So, in order to be able to drive it I have to force the Loop to close through my scanner to get the fuel trims working so it's drivable.

2) Fuel trims pretty much remain constant throughout the driving range of rpm's with both long trims pegged at 25% B1ST 54% B2ST -1%

3) On my scanner I can force the O2 heaters on... the numbers seemed to bounce a little and the 4th is not reading probably because of an open on the O2 harness input.

Haven't swapped the O2 sensors yet nor have I corrected that fuel line restriction at this point. I also need to track down the other end of that signal wire from the B1S1 O2 sensor.

Well, thankfully the problem followed the O2 sensor. Lucky me it wasn't the signal wire. Thank God

OK... got the O2 problems straightened out. I found out there are 2 style of O2 S1 sensors for this truck. I had the Canada O2 sensors in which my truck wasn't built there. It shouldn't make a difference but it does. This is why the first set of O2 sensors oddly didn't work. Trims got slightly better because the correct sensors are in. But I still have one bank LT at 25 and the other is like 21 at idle.

I also removed the kinks in the fuel supply line... so it wasn't that. Damn it.

Here the following reading:

At Idle STFT Bank1 = 1%, STFT Bank2 = 4%, LTFT Bank1 = 24%, LTFT Bank2 = 16%

At 1000 rpm STFT Bank1 = 7%, STFT Bank2 = 5%, LTFT Bank1 = 21%, LTFT Bank2 = 14%

At 2000 rpm STFT Bank1 = 3%, STFT Bank2 = 6%, LTFT Bank1 = 17%, LTFT Bank2 = 8%

At 3000 rpm STFT Bank1 = 19%, STFT Bank2 = 14%, LTFT Bank1 = 3%, LTFT Bank2 = 1%

Truck does run better now that all the O2's are working properly and goes into Closed Loop. Would a leaky exhaust manifold gasket cause these problems since I can't find a vacuum leak. Cause while getting into the gas pedal going down the road I thought I heard an exhaust leak from the right side, passenger side, while racing the motor in passing gear but both Long Terms are maxed not just one side.

Thanks

I have to try that check that hakachukai had mentioned.

You really need to solve your cylinder 6 ( bank 2 ) low compression problem.


EDIT
I misread the fuel trims above as negative. I don't know why. Sorry about that.
That makes everything that I said below irrelevant:
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Bank2 is running more rich than bank1 probably because of all of the raw fuel flying down the pipe from cylinder 6 not being able to burn it properly.

However, both banks are running rich.

Assuming that your fuel pressure is still around 50psi:
You previously mentioned replacing your injectors with higher flow injectors. Maybe try putting the original injectors back in and see if that solves your rich problem.
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END EDIT

This part still applies:
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I'd also do an EGR bypass just to simplify things. I recently found out how much a leaking EGR valve can seriously mess with your fuel trims.
If it's the flange type, just unbolt it, cut a gasket for it that has no hole and bolt it back down ( for diagnostic purposed only ). DON'T leave it like that.

Fixing exhaust leaks never hurts either. The easiest way I know of to find those is the start it up and let it idle while reasonably plugging the tail pipe with some cloth ( or something like that ).

If you have no leak, pressure will build in the exhaust until it either blows the cloth out, or the engine stalls.
If you do have a leak, it will be super easy to find because of the pressure. Just crawl under there and look for the exhaust shooting out of the pipe sideways.

Thanks hakachukai… I have to check the EGR valve as you mentioned... plus what kind of ass designed the pcv valve as part of the valve cover?

Well, we can rule out the EGR valve because that engine that year didn't come with one. It's like deciphering it's history... lol