06, 5.3, Was running bad

[SpareParts]

Was over at a guys house today because his truck was running VERY bad!!!! He had changed the fuel pump and throttle body with new.
He was trying to use a cheap scanner that would not read any codes and would not clear any either.
Hooked my scanner to it and i could not get any codes. I assume he had already cleared them so none had set yet again.
Looking at live data i could not see any reading from the O2 sensors. Zero activity from all 4. Ok good place to start looking.
Checked all the fuses, all good. Wiring looked fine.
So i was kinda thinking something was wrong with the ECU but wanted to do a little research before digging into wiring diagrams, test lights and multimeters.

For what ever reason i clicked clear all codes on my scanner when it was running even though it had no codes.
The truck went nuts for about 5 seconds. After about 10 seconds the truck was running perfect. Checked and O2 sensors were reading like they should.
After about 20 minutes running, it was still all good. Fixed (i think) and now he owes me lunch.

Anyway i have never had clearing codes fix anything but on this truck it fixed everything.
Anyone else had this happen or have i never been this lucky?

 

[strutaeng]

Self-healing automotive technology! Hell yeah! Lol

No idea what could have been going on there, but if it's fixed, it's fixed.

When faced with a situation on O2 waveform and stuff seems pegged out high or low, you can always induce an opposite lean or rich condition while engine is running:

1. Temporary unhook a vacuum hose and see if the waveform changes any. Should obviously shift to lean.

2. Spray some carb cleaner into the intake. Waveform should become rich.

You can easily determine dead O2 sensors vs correctly reporting O2 sensors that are simply pegged from a really lean or really rich running conditions.

On the O2 waveform, what's lean vs rich on the low voltage vs high voltage on the graph? I think I read this: Low voltage is Lean...

 

[SpareParts]

Self-healing automotive technology! Hell yeah! Lol

No idea what could have been going on there, but if it's fixed, it's fixed.

When faced with a situation on O2 waveform and stuff seems pegged out high or low, you can always induce an opposite lean or rich condition while engine is running:

1. Temporary unhook a vacuum hose and see if the waveform changes any. Should obviously shift to lean.

2. Spray some carb cleaner into the intake. Waveform should become rich.

You can easily determine dead O2 sensors vs correctly reporting O2 sensors that are simply pegged from a really lean or really rich running conditions.

On the O2 waveform, what's lean vs rich on the low voltage vs high voltage on the graph? I think I read this: Low voltage is Lean...

Yeah, i know all that. All 4 of these were reading 0

 

[Fless]

Wonder what the fuel trims looked like before? Is there a chance that your code clear also cleared the long term fuel trims?

Is it a Flex Fuel engine? Just a SWAG but maybe it was thinking it was running E85 but is really just gas.

 

[SpareParts]

its a 06. Flex fuel i don't think so. Fuel trims were all 0 and O2 sensors all read 0.
After clearing the nonexistent codes O2 sensors were normal and STFTs were 0/-3 LTFTs were -10 and -14
I told him if anything pops up to let me know.

 

[Fless]

Good to know, and a strange situation. If he has further troubles, please update us.

 

[Doubeleive]

couple things just to note
if equipment was replaced, depending on what it was, the computer may not recognize it being any different until either the battery is disconnected or the computer is reset (in-particularly 02 sensors, even though in this case they were not replaced, it is noted in the service manual to do a reset when replacing them) .
there also could have been a bad handshake between modules (communication error) and clearing the computer resets that very much like disconnecting the battery.
same situation can happen if you do disconnect the battery but when reconnecting it you inadvertently touch the terminal but it is loose and looses a brief connection, wiggle the connectors, etc. this also can cause a bad handshake between modules.

 

[swathdiver]

I reckon that useless scan tool screwed up the engine computer until you "fixed" it!

 

[SpareParts]

Well he started it up and went to drive it and it started running bad again.
Got to be an electrical problem either connection's or ECU.

 

[Fless]

Check those PCM connectors for water migration while you're at it.

 

[SpareParts]

I do not know if i'll see it again. I did tell him to look at the connections at the ECU when he txt me.
I also told him we know it is capable of running right as it was running fine when i left.

 

[LsHart]

its a 06. Flex fuel i don't think so. Fuel trims were all 0 and O2 sensors all read 0.
After clearing the nonexistent codes O2 sensors were normal and STFTs were 0/-3 LTFTs were -10 and -14
I told him if anything pops up to let me know.

On a cold start up, the 02 sensors are not active. After about 15 minutes or so the computer starts asking the 02 sensors for readings. It's for start up and warm up time.

 

[SpareParts]

Yes. I'm aware of that.
It goes by temp, not time.

 

[LsHart]

When u cleared the codes, were u able to reset the fuel trim? Some scanners will not.

 

[LsHart]

Just asking.

 

[LsHart]

not to vier but, my Solus Snapon scanner will only let me reset certain vehicles.

 

[SpareParts]

There were no codes showing to clear. I can reset fuel trims but did not.
My new scanner will do a lot more than the Solus Pro i had.

 

[LsHart]

Any updates on this issue? Really interested in the fix.

 

[SpareParts]

None really. The fallowing weekend he was moving it around the yard and it started doing it again. All i know.