abs/speedo issue on 6.0 cam swap 2007 tahoe

[Jjona5]

So my 2007 5.3 tahoe 4wd has an issue but no codes. When I come to a slow stop I feel the abs kick in sometimes. I've replaced the speed sensors. This started when I swapped in a rebuilt 6.0 with tsp stage 1 truck cam. When I'm on the freeway the speedometer gets off. When I'm running up to about 40 its pretty much spot on, as I get faster it gets off. When my actual speed is 75 it reads about 55 on the speedometer. The tires are new and match. The tuner said he didn't modify the tire size/ratio. I didn't have these problems at all before the swap and like I said, no codes. I did have the service 4wd light come on once on the freeway. I got under the truck and the connector on the diff is good. I don't see any damaged wires. I don't have one of the high end code readers to spin the tires and check the speed at the computer. I just have a bluetooth and torque. I do have a nice multimeter though. I might try getting a wiring diagram and probing at its furthest point sensor by sensor to see what I get.


Any ideas?

 

[Fless]

Not sure about Torque Lite but Torque Pro ($5) has PIDs for all four ABS wheel sensors, as well as transmission in and out speed sensors. Have the vehicle-specific GM PIDs been added to your Torque app? If so, and if they report, you should be able to graph and monitor them.

 

[Jjona5]

Not sure about Torque Lite but Torque Pro ($5) has PIDs for all four ABS wheel sensors, as well as transmission in and out speed sensors. Have the vehicle-specific GM PIDs been added to your Torque app? If so, and if they report, you should be able to graph and monitor them.

I do have torque pro. I'll need to figure out how to add the GM PIDS. Thank for the tip!

 

[Jjona5]

Sweet. Added. I'll go drive her around tomorrow and see what it says.

 

[Jjona5]

So the 4 speed sensors arent reading...neither is the transmission output speed.

 

[j91z28d1]

if none of them are reading it's probably just not the correct pids for your truck. I wish I knew how to find pids, but I don't. there's. a super long thread about it on the trail blazer board. they might have some in there.

but it definitely seems off. that's why your abs is kicking in when it shouldn't. if it's worth 375$ scanner to you to fix it. one of the clone tech 2's will read all that and tons more. they are pretty invaluable if you work on your own stuff with odd problems like that.

I'm pretty sure your turner's software will also do it. hptuners has a pretty decent diagnostic tool to it. you could take it back and ask him to go for a ride with you and find out why your speed is wrong. he might not have touched it, but something happened and unless it's a sensors going bad, which does happen but usually they work or don't. it's probably something he's going to need to adjust to fix anyways.

check the steering angle sensor too. see if it looks normal. if they hand the shift off to swap motors something might be missed up, and the truck thinks you're turning while stopping so it uses the abs to keep you from spinning out. I've seen that on my own car with a steering ratio quickener. trips the body control module out.

tires are factory size front and back?

 

[Jjona5]

Yup tires are factory size front and back and brand new(less than 200 miles on them). The ABS issue seems to have stopped(happened one time after the new sensors) but the speedo issue remains. I also watched my torque pro this time and verified that the computer vs gps speed is way off at freeway speeds. To take the speedometer out of the picture.

 

[j91z28d1]

since you've used a tuner, I'd swing back by. hptuners makes it super easy to adjust speeds. wouldn't surprise me if he started with a base 6.0 tune for your truck that he had already done and was copying over stuff. he changed something to do with mph and didn't realize it.

that's how most tuners do it, once they have a good tune on a combo close to yours, they start with that base each time and then make little tweeks, rather than start from scratch each time.

 

[Jjona5]

Yeah I actually asked that specific question and he said he just modified my tune. I thought the same. I will be taking it back...final tune was supposed to come after I put 500 miles on it.

 

[j91z28d1]

tuners can be kinda odd people. if you get one that's high strung you gotta treat them with kid gloves.. it's annoying sometimes. but if he's dead set he didn't do it. just agree and ask him to cal the speedo in the tune and go from there. that data from tq app that shows GPS speed and speed sensor speed should be all he needs. there's a box on hp to plug those 2 numbers in, hit calculate and it spit out a number and asks if you wanna flash it.

mine was only 2mph off but I adjusted it anyways haha cause it's there and I used the credits already to disable the afm.