Electrical - where to begin

[Moosemoon]

Hi All,

I am a septuagenarian lady with a 2001 Yukon XL 2500 4WD SLT 6.0l.
In Feb 2021 I took my Yukon to a guy to have it refurbished and painted. I did not get it back until Feb 2023. TWO full years. It is a mess!

So I am left with a persistent P0332 (knock sensor), airbag codes, and other codes that come up on my scanner but the dealer now can’t replicate.

Knock sensors have been replaced both by original guy and another shop. Still have service light on and code.

Dealer mechanic says it’s all electrical. I tend to agree. Says he looked at the harness under fuse box and it appears good, i.e. not a rodent nest. Says they can’t troubleshoot the airbag stuff because it is a historical code that was cleared by the shop who replaced the O’Reilly sensors with the AC Delco ones. Is that true? All the other ‘historical’ codes I get were cleared by the second shop but are unresolved on my scanner and, as mentioned, do not even show up for the dealer.

SO - if this is an electrical mess - can anyone advise me as to how to begin troubleshooting it?

Dealer says ‘many hours‘ to diagnose @ $131/hour. AND they can’t even begin to look into it until May!

If you all can at least point me in the right direction ???

I’m not the best at electrical stuff but am willing to give it a go. In the last few weeks I’ve learned more about my beloved Yukon than I knew there was to know.

Many Thanks!

 

[Donal]

A lot of imagination required here, so resort to basic operation. Check engine oil, coolant levels, adjust if needed, belt tension.
Insert ignition key and rotate to ON position. Note 7 flashes of air bag icon, air bag icon stays on or not. Start engine, noting oil pressure, coolant indicated, fuel level indicated. Check under vehicle for drips/ leaks, etc. All good sofar. Note CEL on or off or flashing. CEL not flashing, operate normally. Note oil pressure, coolant temperture, fluctions on any gauge, etc. Take the vehicle through several short trips to cycle through ignition on/off, engine run, engine off. If the CEL light is on, use your scanner to identify and RECORD error codes on paper.
Apparently you are in a area where dianogistic services are in very high demand and no one has time to assist you. Most all of the members on this forum are willing and able to assist, if your location was known, some near you may be able to do hands-on assist.
Note that the vehicle was neglicted for almost 2 years and sufferes neglected vehicle anxiety. All ground connections tend to corrode and develop resistance. Each connection may have to be cleaned. The computer modules resists reactivation and need several operation cycles to relearn and commuicate with each other.
If the air bags have NOT been deployed, the system is responding to a high resistance test result. The seven flashes are the tests being performed. This april fools day. So, I am responding just in case you dont have a calender.

 

[OR VietVet]

Like @Donal said about 3/4 way thru the recommendations. Got to start somewhere and my money is on checking EVERY ground point connection for tight, corrosion and even if is connected at all. I personally would not advance far in to this till that "must know" item is done. That rig was somewhere else for 2 years and almost anything could have happened with the rig while in the hands of MR. SLOW MO! Diagnosing electrical problems, especially if intermittent, can be a nightmare and expensive. Hopefully someone here can supply a diagram of all ground points. If not, you can always pay $60 at ALLDATAdiy.com and get vehicle specific info and diagrams. Good luck.

Post where you are at and maybe a member can help personally or recommend a quality shop in your area. For instance, I know a great guy and shop in my area in the Willamette Valley of Oregon.

 

[MassHoe04]

Main grounds should be easy enough to locate, even without a diagram.

Negative wires from the battery... Follow to the far ends.

Grounds on the back side of the engine block and ones that bolt directly to the fender or firewall.

Grounds for inside stuff are on the driver's side, inline with the door hinges.
Look underneath, where the body mount sticks out from the frame rail.
There are two locations on there that have black wires bolted to that body mount.

Disconnect the battery, remove the bolts on these main ground points, clean all points of contact and the terminal connectors, replace bolts, tighten and spray the area with paint/primer or something to slow development of corrosion.

(I am on break at work... I don't have access to diagrams...)

 

[Onlyone]

First things first. Check the battery. Then, meticulously check grounds.

 

[MassHoe04]

First things first. Check the battery. Then, meticulously check grounds.

Oh yeah... The obvious. Do that^^^. I may have skipped ahead one step!

 

[Doubeleive]

Hi All,

I am a septuagenarian lady with a 2001 Yukon XL 2500 4WD SLT 6.0l.
In Feb 2021 I took my Yukon to a guy to have it refurbished and painted. I did not get it back until Feb 2023. TWO full years. It is a mess!

So I am left with a persistent P0332 (knock sensor), airbag codes, and other codes that come up on my scanner but the dealer now can’t replicate.

Knock sensors have been replaced both by original guy and another shop. Still have service light on and code.

Dealer mechanic says it’s all electrical. I tend to agree. Says he looked at the harness under fuse box and it appears good, i.e. not a rodent nest. Says they can’t troubleshoot the airbag stuff because it is a historical code that was cleared by the shop who replaced the O’Reilly sensors with the AC Delco ones. Is that true? All the other ‘historical’ codes I get were cleared by the second shop but are unresolved on my scanner and, as mentioned, do not even show up for the dealer.

SO - if this is an electrical mess - can anyone advise me as to how to begin troubleshooting it?

Dealer says ‘many hours‘ to diagnose @ $131/hour. AND they can’t even begin to look into it until May!

If you all can at least point me in the right direction ???

I’m not the best at electrical stuff but am willing to give it a go. In the last few weeks I’ve learned more about my beloved Yukon than I knew there was to know.

Many Thanks!

Can you please clarify if these are active codes with check engine light on and airbag light on. Or are they simply historical codes? You can disregard about 3/4 of the nonsense that has been posted thus far

 

[Moosemoon]

Thank you all for your input.
All the most basic stuff - oil, fluids, etc is in order. No drips or leaks.
The CEL (service engine soon in this rig) IS on. Code P0332
Restraint System light does NOT stay on. Airbag codes have registered every time I scan, starting a couple days after I picked up the rig. Those codes are B0029, B0041.
Other codes - which all say - test not passed since DTC cleared and that the dealer could not replicate are:
P0719: Brake switch control low voltage
P1172: Fuel Transfer Pump Flow Insufficient (this would be the pump from the small tank to the big tank)
P1431: Fuel Level Sensor 2 Circuit Performance (which I believe is the small tank)
And, of course, the aforementioned P0332 Knock Sensor 2 Low Voltage Bank 2 code.

The Yukon is guzzling gas. Never was thrifty but now ridiculous.

I had noticed that my dash lights seemed dim and didn’t change much regardless of headlights on or off. Small bump in the road this morning and now the lights are functioning normally.

Have the Alldata subscription. Will get the diagrams. In the meantime - will begin with the basic battery and ground checks. As soon as the wind and snow stops from our latest winter storm.

I live in the Idaho Falls, ID area.

The Willamette Valley isn’t all that far. I might take you up on the referral. Got 1 other guy to try here.

Thanks again for the input. Any and all thoughts about this are certainly welcome!

 

[Moosemoon]

Oh, I should note that while MR SLO-MO had the Yukon, the transmission was rebuilt and the engine was gone through.
Basically, if there was a part he could take off, he did so. Lots of bolts in little plastic containers. Which is why I sorta had to wait for him to get it back together and didn’t just haul it away from him.

The Yukon and I are both suffering from ‘neglected vehicle anxiety’!

 

[Doubeleive]

It's possible if the steering wheel was removed maybe the airbag is not connected properly the other code is a impact sensor those are known to go bad from age