Check Engine Light and 4WD Service light on 2018 Denali 1500 after install of Air Lift 5000 bags for my RV towing.

kbren · January 5, 2019

Long story short after installing my Air Lift 5000 bags I went to turn the car on to calibrate the Smart Air system for the air bags with manual air before hooking the on board air compressor relays up to ann Ignition source and I was getting limp mode via Check Engine and Service 4 wheel Drive Soon lights while the engine was low on power and shifting abnormally (had to drive it to the air compressor).

I can't imagine the airbags did anything to the tune (they just mount to the axles) and regarding the Smart Air II system, I merely hooked their relays up to the negative battery post and the positive battery blocked right above the pos battery post. Again, I never even finished the power by hooking up an Ignition source before these codes triped.

When it happened I disconnected the negative battery terminal and reconnected it and the lights were gone for half of a day and then everything came back on.

At this point, I took it to the dealer because I do not have a scan tool to check the codes in whatnot. The dealer is telling me that they had one of their "best electrician" on the it and he cannot figure out the problem they thought maybe I pinched an ABS brake line but they are now saying thats not the problem and they can't even reset the codea now because every time they do they come right back on. Service guy thinks there I might of done something to TCM by hooking up the fused positive wires for the relays to battery block on the positive side because he said that is a temperamental block post that directly goes to the TCM (head scratcher). I have a hard time believing that because it's just a large fuse aperture coming right off the positive battery terminal so I don't understand how that would have anything due to TCM.

Any help is appriciated!

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silveradosid · January 6, 2019

did the dealer tell you what the codes were

kbren · January 6, 2019

Not yet. I'll get them on Monday and share... What a pain.

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Nitrousbird · January 6, 2019

#1 mistake (too late now, but don't do it again) is taking a vehicle anywhere, even for warranty work, without knowing the codes first. Knowing the codes gives you a leg up on anything they try to feed you.

This is what I use. Reasonable price and the best priced unit out there that will give you more than just basic OBD codes (will do BCM and other modules - very useful stuff). It paid for itself a couple times over with my last truck. https://www.amazon.com/dp/B00652G4TS/ref=sxts_kp_bs_1?pf_rd_p=8778bc68-27e7-403f-8460-de48b6e788fb&pd_rd_wg=csHgV&pf_rd_r=ZRD3GYJRA9P76HJSZ99Z&pd_rd_i=B00652G4TS&pd_rd_w=zOHsk&pd_rd_r=0623044b-95c3-4256-863f-21c5005e3857&ie=UTF8&qid=1546799631&sr=1

#2: If their best guy is throwing out ABS causing a limp mode issues, I'd be HIGHLY suspect of anything they told me. You could have cut every ABS wire in the truck and it won't throw the motor into limp mode (it will light up the dash for sure).

kbren · January 6, 2019

#1 mistake (too late now, but don't do it again) is taking a vehicle anywhere, even for warranty work, without knowing the codes first. Knowing the codes gives you a leg up on anything they try to feed you.

This is what I use. Reasonable price and the best priced unit out there that will give you more than just basic OBD codes (will do BCM and other modules - very useful stuff). It paid for itself a couple times over with my last truck. https://www.amazon.com/dp/B00652G4TS/ref=sxts_kp_bs_1?pf_rd_p=8778bc68-27e7-403f-8460-de48b6e788fb&pd_rd_wg=csHgV&pf_rd_r=ZRD3GYJRA9P76HJSZ99Z&pd_rd_i=B00652G4TS&pd_rd_w=zOHsk&pd_rd_r=0623044b-95c3-4256-863f-21c5005e3857&ie=UTF8&qid=1546799631&sr=1

#2: If their best guy is throwing out ABS causing a limp mode issues, I'd be HIGHLY suspect of anything they told me. You could have cut every ABS wire in the truck and it won't throw the motor into limp mode (it will light up the dash for sure).

Very well stated. I am getting the truck from them tomorrow no matter what they tell me.

I have that code reader on order. I'll get this figured out. After reading codes and doing self diagnosis I'll update but bottom line, if I take it to another dealer it will be the one further away from my house. The one it is at now is by far the worst I have had the pleasure of dealing with...

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