Lawman86

So as my previous threads have stated, I bought the truck from a dealership who’s basically after I threatened to get my lawyer involved they said they couldn’t have any further communications with me all because they refused to fix the mistakes they made. I go in today to look into the wiring under the dash and noticed a red wire, and a blue one going under the carpet, well got to looking and it’s running to the fuel pump. I found a receipt where they replaced the fuel pump and instead of wiring it the right way they spliced into what looks like the plug in for one of the air bag plug ins. They skinned the wire back and soldered it onto a known key on/hot. Well then I seen these wires dangling from a loom right under the dash, it’s a factory loom and even had the wires labeled under the dash but didn’t say to what. So what are these wires for? I used the multimeter and didn’t get any power from them, so not sure what they would go to. All I know is I’m more than pissed at the poor workmanship these people did. I’m taking it to the dealer soon to get the speedometer fixed because it’s +/- 10 over, and the service air bag light is on, but it also has the recall on the air bag. So what gives, what are these wires to, and where would the fuel pump hot wire originate from anyways. I think what happened is one of the block grounds broke off, the main one on the back of the block and that’s why they hooked it up to the hot the water they did, why I say this is because I found the hood to body ground laying in the engine compartment. Anyways, y’all got ideas on these wires, and where the hot for the fuel pump would actually go so that I can fix their mess?

Here’s what puzzling to me, when the truck is in gear, with the foot on the brake the needle is above zero. My Denali you can put it in gear and it won’t move anywhere above zero unless you’re going 2-3 mph, and is steady all the way. This one here shoots us like a rocket on the interstate. Here’s a pic of it on the interstate today (this is after I put in a VSS in the trans), and going 75. It’s showing 85 on speedo so it’s + or - 10 off depending on road conditions, and the needle goes above zero before you even move. When it’s in park it’s well below zero.

This is how annoying it is. I went ahead out of my better judgement and put a VSS in the tail shaft on the trans, and also a passenger airbag sensor, I am having to reschedule my appt for the dealer. I’ve got a sick 3 year old, but I did notice when the truck is in gear and foot on brake the needle is above the 0 mark, not normal cause my last one heck you put it in gear and it stayed below zero as if it was set to give it a mile or two slower before the needle would move. It was so accurate that I had it set like clockwork everyday for all the speed traps. I’m sending a few pics. One is at rest with foot on brake with it in gear, the other one is on the interstate with cruise set at 75 and it shows 85. I got my multimeter and ohmmeter earlier to work on some other stuff. I noticed even though my truck came with the RPO package for electric start they put a aftermarket antenna inside the vehicle but of course didn’t have that key.

I don’t necessarily have any good shops around me, dealers anyways. I’m an ASE Master Mechanic but when you don’t have a scanner like the ones you had at a dealership it makes it real hard to do what I was used to doing. I was a shop foreman at the time, but I helped a lot when I was bored or wasn’t doing warranty tickets. If I had the extra few grand to get a good OBD2 scanner where I could do most of the calibrations it would be nice. The one I have does some ABS stuff but not airbag stuff or some other important stuff. I’m going to take it down there and have them replace the passenger module because I looked it up by the VIN and it’s never been changed, and that may be what my issue is, plus they can delete the light for me, also I am pretty sure if they’ll put the stock setting on the tires it’ll likely fix it. It’s about + or - 10mph, depending on if the road is flat

Yeah I’m from Arkansas, the land of where they never salt the roads unless there’s a 100 wrecks I’ve checked all fuses, plug ins under the seats, and everything I can think of and even replaced that nasty looking front module. I did notice when I first got the truck that the code c-0899 was on. I’ve read that under current or even an alternator can cause this. Which mine hasn’t been an alternator issue but did have that one code stored. I used my scanner and deleted it but I think I’m going to contact the dealer and tell them about it. I know my speedo is also off by about 5-8 mph. Which is super annoying especially when you’re on the highway and going 5-10 above posted speed and you look down and it makes you think you’re actually going 20 over. I’m not sure if the original owner had larger tires or not because the ones that are on it are stock size, but doesn’t mean they didn’t change them out. I am going to the dealer on Thursday and will mention the airbag issue. I was taking it in for the speedo issue. I thought the needle was sitting a little higher above zero while sitting still but it’s not. I was just going to adjust the needle, but I’ll have them look at it and try to readjust, because even with my scan tool doing live data it’ll show the speed of the speedometer instead of actual speed, so the computer evens thinks it’s going that fast. Yeah I worked in law enforcement for almost 12 years. I am medically retired now, but remember all the storm vehicles because I have my meteorology degree, that the sheriffs dept paid for when they decided to be generous to pay for continuing your education, so I got tasked with working Emergency Management, and also disaster relief and search and rescue for Hurricane Katrina, Moore, Joplin tornadoes, Hurricane Harvey, and several smaller tornadoes. I did the Carfax on it but it showed it was bought from the southern states and shipped up north to a dealer and they never sold it, instead it was labeled as “dealer” vehicle, then the place I got it from had bought it from an auction that the dealership up north had. It’s so aggravating to have these little issues, but it’s not the end of the world. If I could just get the speedo issue fixed I’d be happy with that at the moment. I have a decent sized personal injury settlement coming so paying this off should be easy and I can get these issues fixed and use this as the hunting rig or whatever

So I got the truck with the service airbag light on. I did some looking around and no codes are showing up on my scanner, but I don’t believe mine will show the parameters for the Air Bag system. I looked at both the frontal air bag sensors on the bottom of the core support area, and the passenger side one was cracked almost completely ONLY where it screws in at. The actual portion to the front wasn’t broken but both sensors look horrible. Truck came from the North, and so they are corroded as can be. I replaced the passenger side one. Hooked battery back up and it’s still on. I also looked under passenger seat, and drivers seat and the plastic cover that goes over the wiring to conceal them the one on the passenger side was missing, as well as the yellow plug in little plastic rivet that holds it onto the metal plate. So to me it looks like someone has messed with the passenger side wiring under the seat, whether intentional or not, but I guess I’ll have to take it into the dealer to get them to hook it up to the OBD2 port to see if they can erase it. Anyone else ever have this issue? I also noticed my chime doesn’t come on when my seatbelt is off, I’m assuming because my service airbag light is illuminated the entire time.

Somethings up too. I just realized this had the 6 speed. After looking at the RPO codes. I guess I’ll take it to the dealer to have them calibrate it back to the original tire size. It’s either that or the VSS on the trans is off.

So I bought the truck. Didn’t notice the speed was off by 10 until I got onto the interstate, and people passing me. I checked tire sizes, all factory sizes, hooked up my scanner and oddly enough the speed on OBD2 scanner read the same as the speedo. So after checking and verifying tire size was correct, and checking seeing that it was being sent via OBD false as well I am stumped. At 60 I’m going 48-50+/-, and at 85 it’s really going 75 +/-. What’s your observations? It’s on a 2011 GMC Sierra Cree Cab 4wd, all auto. In the photos I was going what was supposed to be 40 and it shows 50 on speedo, and on GPS it shows 45. So it’s + or - 5-10 at low speeds and at 75 it will show 85. What do y’all think. I’m retired ASE Master engine tech and can work on these but I was in the diesel industry. So while working on vehicles are nothing new. This speed has me stumped. I don’t want to take it to dealer if it’s the VSS on the rear of tail housing near transfer case, and I’ve also heard of a VSS Buffer? Someone elaborate a little on whether it could be related to that. There’s a ABS light flashing on OBD scanner but no active codes.