One last shot... Breaking up!

BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

WyoSyclone said:
Well, let's see.... if the O2 is disconnected and the problem persists, it could be that the purple wire is still shorting directly to ground, presenting the ECM with a false signal.

Did the bypass capacitors get installed on the wideband wiring between B9 and E14?
Click to expand...

Yes, there were 2 bypass capacitors but I only used one. Either way this problem started prior to the WBO2 install.

Now as far as the O2 being disconnected... I watch the O2 Parameter on the DM last night with O2 disconnected and the O2mV bounced back and forth 453 and 457. They did not move when breaking up occured and the truck stayed in 'Open Loop'. I'm not sure what the mV should read with O2 not connected?
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

BoostedSUV said:
Yes, there were 2 bypass capacitors but I only used one. Either way this problem started prior to the WBO2 install.

Now as far as the O2 being disconnected... I watch the O2 Parameter on the DM last night with O2 disconnected and the O2mV bounced back and forth 453 and 457. They did not move when breaking up occured and the truck stayed in 'Open Loop'. I'm not sure what the mV should read with O2 not connected?
Click to expand...

Well, we are getting it narrowed down!

With the engine at operating temp, turn engine off, disconnect O2 sensor.
Jumper the purple wire (ECM side) to ground. Restart engine. O2 voltage should be below 200 millivolts.

If not, turn engine off and remove jumper.
Turn key to on, engine off.
Check voltage of purple wire (ECM side). If 300-600mV, the ECM is bad.

If over 600mV then a faulty connection (intermittent, or bad ground on Black/white), or a bad ECM.

If less than 300mV, faulty ECM connection, or faulty ECM.

This is just straight out of the service manual.

So, according to the test you did, this factory info would say the ECM is bad (but do it with the engine off as they state to verify). You should ground that purple wire with the O2 connector disconnected and see what the voltage is (it's supposed to go down below 200mv).
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

I will have to read that more thoroughly when I get home and when I'm in front of the truck. I just straight up disconnected the O2 and started the truck, let it warm up and watched O2 mV on DM. I also didn't have the purple wire grounded so my numbers are meaningless. I will try that way tomorrow night.
 
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BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

TYTILIDIE said:
Sounds normal to me if wire was connected. You said it did this before your MSD dist?
Click to expand...

Yes I remember going to Auto Zone and picking up an ign module and changing it on my stock dizzy when I chased the same issue a few years back.
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

So are you going to change the ECM and EEPROM again?? ;)

If it ends up being the solution again I'd wonder why it failed a second time.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

Follow me on this one...

Take ECM down to put in Ultimate chip back in 06, problem starts, change bunch of crap with no results. Put in new ECM truck is "fixed"

Take ECM back down to put in Moates adapter for custom chip when I do vortec swap and problem is back (not discussed on here since I was working with Nolan and assumed it was tune) go back and forth changing eproms and problem is "gone" so I think it was tuned away

Working around back of ECM to remove wire for A/F gauge (first post in this thread) problem is back worse than ever. My first move, thinking back to 2006, change ECM. Does nothing this time.

Read back in 06 and now, code 42 pops up occasionally.

Now for my theory: I'm going to be looking for a needle in a hay stack. I've got a broken wire in the ECM harness and moving ECM around upsets it, or makes it make connection thus "fixing" the problem. Based on wacky O2 reading I would say purple O2 wire as Wyo suggest, or a wire to ign module which explain random code 42 and ignition misfire? Any thoughts? Follow all that theory?
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

That's exactly what I would look for.... start with the obvious wires first. It's a real rat's nest up where the ECM sits. When pulling the ECM in and out it's really easy to nick a wire on the edge of the dash bracing if you're not careful.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

How hard would it be to pull the whole ECM/engine bay harness out of the truck so I can spread ir our on the floor and follow wires easier? Couple plugs, couple grounds, drop the inner fender well? That way I can go over it with a fine toothed comb instead of what I can just see which isn't much!
 
leadfoot

leadfoot

Member
Re: One last shot... Breaking up!

Before you do that -get a good magnifying glass and a bright light and check the connectors and pins and as much of the exposed wire as you can.
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

leadfoot said:
Before you do that -get a good magnifying glass and a bright light and check the connectors and pins and as much of the exposed wire as you can.
Click to expand...

x2..... if it's a bad terminal end (wire broken at edge of terminal) it should be pretty easy to see. If it's an open on the insulation of a wire that should be easy to see as well (just a hole in the insulation).

Did you use factory terminals to connect the PLX to the ECM?
 
thunderace31

thunderace31

New member
Re: One last shot... Breaking up!

WOW At least you have a good place to look and man it makes total sconce to me that that would be the issue! Thats a tight space in there Id say pull the harness but after looking at mine a little bit ago I think that you would have to pull the dash to get the whole thing out but maybe someone else will know better :)
Great work and I cant wait to hear its fixed!
:tup:
 
S

Syclone #1721

I LOVE 4UM SUPERSTARS
Re: One last shot... Breaking up!

You said you did a continuity test on every wire from the ECM didnt you...maybe I misread it but I thought you did......that should eliminate it unless like you said, its going open when you put the ECM back in its mount.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

Yes I did to a coninuity test on every wire off of the ECM, I also used a small drill bit and made sure every terminal was tight on the pins on the ECM. This is the only thing I can seem to make sense at this point and after going back old threads of mine. Right now the ECM is on the floor so most of the wires are visible. I know I looked through them all but I feel like maybe I missed something. Its a long shot but I will try again! I real need someone here to watch the VOM while I jiggle wires but its hard to get good help when I need it!

Rob I used factory termals from and old harness I had to connect the WBO2. I just plugged them into open sockets as per Digs instructions on his website.
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

One trick when doing it by yourself is to set the DVM to beep upon sensing continuity. Just clip the black lead to a good ground and then you can probe each wire, shake the bejeesus out of it, and just listen for the beep.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

I would think I'm looking more for a broken wire rather than one shorting to a ground. Maybe not? I will certainly try that too
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

BoostedSUV said:
I would think I'm looking more for a broken wire rather than one shorting to a ground. Maybe not? I will certainly try that too
Click to expand...

Well, one or the other... You can do the same trick when checking for a broken one... clip to each end, beep will be constant, listen for it to stop... Wish I could come out and help look for it.... :D
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

Thanks Rob, just thought about that after I posted reply. I went back to edit it but you beat me to it. typing before I'm thinking! Lol that's a good thought, just have to look at the VOM and make it beep. Thanks again! Its going to be cold and rainy for the next 4 days so I'm really going to test my determination!
 
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