Electrical - where to begin

[Moosemoon]

If you want to, take a look in your scanner for the short- and long-term fuel trims (STFT, LTFT) for both banks. Post up all 4 values at warm idle, then also at 1500-2000 rpm.

I got values for the 02 sensors but it was during a scan after I tried resetting the Ksenors and seeing if the light came back on. No Light but code pending ….
O2B1S1
1: Rich to LN Threshold = 0.540 (V)
2: LN To Rich Threshold = 0.540 (V)
3: Low V for Switch = 0.250 (V)
4: High V for Switch = 0.625 (V)
5: Rich to LN Time Value = 0.040 (S)
Min = 0.000 (S)
Max = 0.132 (S)
6: LN to Rich Time Value = 0.036 (S)
Min = 0.000 (S)
Max = 0.140 (S)
O2B2S1
1: 0.555 (V)
2: 0.555 (V)
3: 0.250 (V)
4: 0.625 (V)
5: 0.040 (S)
0.000 (S)
0.125 (S)
6: 0.028 (S)
0.000 (S)
0.136 (S)

Hope this is sorta what you were asking for. I don’t think I understand what I’m looking at other than volts and seconds. Thanks

 

[Moosemoon]

I got values for the 02 sensors but it was during a scan after I tried resetting the Ksenors and seeing if the light came back on. No Light but code pending ….
O2B1S1
1: Rich to LN Threshold = 0.540 (V)
2: LN To Rich Threshold = 0.540 (V)
3: Low V for Switch = 0.250 (V)
4: High V for Switch = 0.625 (V)
5: Rich to LN Time Value = 0.040 (S)
Min = 0.000 (S)
Max = 0.132 (S)
6: LN to Rich Time Value = 0.036 (S)
Min = 0.000 (S)
Max = 0.140 (S)
O2B2S1
1: 0.555 (V)
2: 0.555 (V)
3: 0.250 (V)
4: 0.625 (V)
5: 0.040 (S)
0.000 (S)
0.125 (S)
6: 0.028 (S)
0.000 (S)
0.136 (S)

Hope this is sorta what you were asking for. I don’t think I understand what I’m looking at other than volts and seconds. Thanks

Well shoot now that I reread your post - I don’t think this what you asked for at all. Sorry

 

[Fless]

Well shoot now that I reread your post - I don’t think this what you asked for at all. Sorry

The fuel trims will be expressed in percentages; most scanners will read between -25% and +25% and not outside of that range. Good numbers are within +/- 10%, but if you can grab them let's take a look.

 

[Doubeleive]

The harness was replaced with the knock sensors. One set o’reilly; latest AC Delco .Dealer says they are working. There are other codes suggesting some electrical issues and now the radio will not turn on. Instrument panel light is dim - brightened once when I hit just the right bump.

HOWEVER, I’ve read that 50% of ac delco sensors are also bad out of the box. Have no idea if mechanic(s) tested ks before closing up and hoping for the best.

no radio and cluster dim could reflect a poor connection somewhere, where exactly is the tricky part. most commonly it's the ground to the battery.
I would ohm check the ground cable as a place to begin. from "negative battery post to ground point on engine block/head" it should read 0.00
you may have a smaller cable that also splits from the main ground cable and goes to the frame check that as well.
on the back of the engine I think drivers side there is a ground strap there as well it can be difficult to reach you may want a stool or something to give you a lift up.
I know you said you checked the grounds before but a ohm test will confirm they are good

 

[Moosemoon]

no radio and cluster dim could reflect a poor connection somewhere, where exactly is the tricky part. most commonly it's the ground to the battery.
I would ohm check the ground cable as a place to begin. from "negative battery post to ground point on engine block/head" it should read 0.00
you may have a smaller cable that also splits from the main ground cable and goes to the frame check that as well.
on the back of the engine I think drivers side there is a ground strap there as well it can be difficult to reach you may want a stool or something to give you a lift up.
I know you said you checked the grounds before but a ohm test will confirm they are good

Thought I did that but will do again. Yes, the trick is where did slow guy connect things and how badly did it mess up everythin.

 

[Moosemoon]

The fuel trims will be expressed in percentages; most scanners will read between -25% and +25% and not outside of that range. Good numbers are within +/- 10%, but if you can grab them let's take a look.

Think I have some of that from a freeze frame. Will chk

 

[Moosemoon]

Think I have some of that from a freeze frame. Will chk

This is FF from when the engine light came on when on the way home from ksensors & harness being replaced along with O2 sensor. Supposedly all ac delco
STFT B1 = -3.1%
LTFT B1 = 7.8%
STFT B2 = -3.1%
LTFT B2 = 9.4%

veh speed 68mph
engine temp 183F
RPMs 2401

 

[Fless]

This is FF from when the engine light came on when on the way home from ksensors & harness being replaced along with O2 sensor. Supposedly all ac delco
STFT B1 = -3.1%
LTFT B1 = 7.8%
STFT B2 = -3.1%
LTFT B2 = 9.4%

veh speed 68mph
engine temp 183F
RPMs 2401

So those are good at speed, very acceptable. Typically one would add the ST and LT FTs together for each bank. Bank 1 is -3.1 + 7.8 = 4.7%. Bank 2 is -3.1 + 9.4 = 6.3%. Anything under 10% is good, the closer to zero the sums are, the better. But nothing wrong with those.

Positive fuel trims mean that the engine computer is adding fuel since the O2 sensors are reading the mixture as lean. That's what it does, within reason.

They could be different percentages at idle, but I doubt that has anything to do with your knock sensor issue.

 

[Baja_Bob]

I am no engine expert but did this "technician" replace your spark plugs and wires for you? Newer engines with high-energy ignitions need resistor spark plugs, electrical noise/interference may affect surrounding sensors. (like knock sensors). Just a thought.

Check your schematic, the radio and instrument panel might share a common ground inside the dash somewhere, it may be loose, corroded or broken.

 

[Moosemoon]

So those are good at speed, very acceptable. Typically one would add the ST and LT FTs together for each bank. Bank 1 is -3.1 + 7.8 = 4.7%. Bank 2 is -3.1 + 9.4 = 6.3%. Anything under 10% is good, the closer to zero the sums are, the better. But nothing wrong with those.

Positive fuel trims mean that the engine computer is adding fuel since the O2 sensors are reading the mixture as lean. That's what it does, within reason.

They could be different percentages at idle, but I doubt that has anything to do with your knock sensor issue.

Thank You. Good to know info whether or not affecting knock sensor.

 

[Moosemoon]

I am no engine expert but did this "technician" replace your spark plugs and wires for you? Newer engines with high-energy ignitions need resistor spark plugs, electrical noise/interference may affect surrounding sensors. (like knock sensors). Just a thought.

Check your schematic, the radio and instrument panel might share a common ground inside the dash somewhere, it may be loose, corroded or broken.

Hmmm - yes I have a receipt from O’Reilly’s for spark plugs (8) and an ignition wire. I do not have a receipt for spark plug wires but was billed for them but not for the ignition wire. Go figure.
I will check to make sure they are appropriate for my Yukon.
Am studying the diagram(s) to find the ground locations for the radio an instrument panel lights.

Thank you.

no radio and cluster dim could reflect a poor connection somewhere, where exactly is the tricky part. most commonly it's the ground to the battery.
I would ohm check the ground cable as a place to begin. from "negative battery post to ground point on engine block/head" it should read 0.00
you may have a smaller cable that also splits from the main ground cable and goes to the frame check that as well.
on the back of the engine I think drivers side there is a ground strap there as well it can be difficult to reach you may want a stool or something to give you a lift up.
I know you said you checked the grounds before but a ohm test will confirm they are good

 

[Moosemoon]

Doubelieve thanks
I have checked both those grounds more than once and both grounds are good.
There is a short under the dash. I am not sure where. The heater blower motor also has intermittent success at operating.

 

[Moosemoon]

UPDATE: the shop that put in the 2nd set of knock sensors in lived up to their warranty and more - replaced bank 2 sensor and mass air flow sensor. Picked it up and had terrible whistling noise, took it back and they fixed it. Yukon running much better. Sounds like it’s old self. No knock sensor codes pending, no service engine light! Yay!

Still have airbag loop codes, brake switch, torque converter clutch, fuel transfer pump, & fuel sensor 2 codes not passed since cleared.

New code today -auxiliary ECU malfunction

There are definitely electrical things going on that the dealer will hopefully figure out starting tomorrow.

Thanks for helping me to be smarter about how to talk to these folks.

Will update as things get fixed.

 

[Moosemoon]

Dealer was a bust. 2 and a half weeks Not One Thing on MY list is fixed. They did manage to convince me that the upper control arms needed replacing and a leak in the transfer case needed sealed. (Should there have been evidence of a leak on the driveway?)
Of course it needed an alignment after installing control arms - and it pulls to the right now - not drifts - pulls.
And so it goes…. Or doesn’t

 

[Doubeleive]

Dealer was a bust. 2 and a half weeks Not One Thing on MY list is fixed. They did manage to convince me that the upper control arms needed replacing and a leak in the transfer case needed sealed. (Should there have been evidence of a leak on the driveway?)
Of course it needed an alignment after installing control arms - and it pulls to the right now - not drifts - pulls.
And so it goes…. Or doesn’t

maybe try another dealership?

 

[Moosemoon]

Went to other gmc dealer and visited with a service writer. He seemed good and gave me a quote for one thing on my list. Parts guy was good - ordered the clips and screws that I need to reattach the master switch control cover and panel under the steering wheel. Have no clue why dealer 1 didn’t do it. I will do that myself now.
There are also 2 Chevy dealers to try ….

 

[Baja_Bob]

Not all dealers have all the answers, that's why they came up with the upper control arm problem, if it were me I'd put the other problems on hold and focus on the electrical problems your having. Just my 2 cents.

 

[Moosemoon]

Not all dealers have all the answers, that's why they came up with the upper control arm problem, if it were me I'd put the other problems on hold and focus on the electrical problems your having. Just my 2 cents.

Thank you. I agree. Was hoping the dealer would work on the elec issues - not like I didn’t ask them to.
Have figured out that this dealer is an installer not a fixer. Their solution is take it out and replace and hope. They appear uninterested in tracking down gremlins and fixing.

 

[Moosemoon]

The dealer did fix the alignment issue.

 

[Doubeleive]

Thank you. I agree. Was hoping the dealer would work on the elec issues - not like I didn’t ask them to.
Have figured out that this dealer is an installer not a fixer. Their solution is take it out and replace and hope. They appear uninterested in tracking down gremlins and fixing.

you might find this to be the case for all dealers, gm in general does not repair unless it is something related to a service bulletin, just how it is they would rather replace it than fix it.
there are exceptions of course.
electrical problems are addressed with a set choice of parameters, like
a=b
b=c
but if a=c then b must be no good so replace b
it's broken down in steps & procedures, bit more complex than my example but that's a general breakdown
it sometimes helps if you are VERY specific of what you want them to do and then make sure the service writer put's those specifics in the service write up.
there is often very generic or poor communication between the counter monkey and the technician actually doing the work based on the service write up.