Another dang ABS Issue

[zfuller123]

Hello Guys....

Got a question hoping someone might have the magical answer too.

I've been fighting this LBZ and the ABS light since day 1 of working on the truck, and still not making any progress on eliminating it.

The guy used a BullyDog on the truck for quite a while, and since he's had the truck and done all his modifications (ie: 4.56 gears, 37" tires, etc.) he used the BullyDog to change the tire size to get his Speedo dialed in, and it worked great for him.

Since he returned the truck to stock with the BullyDog, the ABS light has kept coming on - even before any EFILive tuning on it. I figured with EFI i'd be able to get the light off by just kinda flirting with different values for the pulse. I have left the gear ratio alone, i have set it to 4.56, i've used the calculator... just about everything i can think of and still the ABS stays on.

I've read posts on here about the issue in the past, as well as some other forums looking for the answer - and nothing seems to be working.

To that end, what i'm thinking is that the BullyDog didn't return everything 'to stock'. Per my understanding, from posts here and elsewhere - the BullyDog changes the BCM as well as the ECM values when adjusting tire size. I'm thinking that the changed value from the BullyDog might still be in the BCM, but it is purely a hunch.

Anyone else combatted this issue and won? I'm not sure whether i need to just try value after value in the truck and see if i can find the magical range or if there is a 'better way' that someone might be able to point out for me.

Thanks in advance!

 

[JoshH]

Are you sure it isn't another problem making the ABS light come on?

 

[TeaBagger2006]

After I put my tires on (37's also) I recalibrated my speedo with my ppe with out any problems. Then my damn abs light came on and I couldn't figure out why,and it was coming on thn going away, checked my wheel speed sensor wire that's on the spindle, the cable had been rubbing on the tire . As soon as I patched it up my abs light turned off....... Don't know why I wrote my whole story :roflmao: hope it helps

 

[zfuller123]

Are you sure it isn't another problem making the ABS light come on?

Not 100% sure, but the light came on and has basically stayed on since the day the BullyDog was removed from the truck.

Going to have him put the BullyDog back on and see if it goes away after he sets it back up how he had it, and if so - the i'll try to get him to set the tire sizes back to stock while BulyDog is still in, and then start up with EFI again and see if we can't figure it out.

If the light stays on, then we'll know for sure something else is up - but he is confident there are no mechanical issues.

If anyone has other ideas please feel free to send them my way! Thanks!

Zach

 

[DAVe3283]

If you've got EFILive, can't you just pull the codes and see what's there? That should tell you if it is another issue.

 

[Chevy1925]

Not 100% sure, but the light came on and has basically stayed on since the day the BullyDog was removed from the truck.

Going to have him put the BullyDog back on and see if it goes away after he sets it back up how he had it, and if so - the i'll try to get him to set the tire sizes back to stock while BulyDog is still in, and then start up with EFI again and see if we can't figure it out.

If the light stays on, then we'll know for sure something else is up - but he is confident there are no mechanical issues.

If anyone has other ideas please feel free to send them my way! Thanks!

Zach

you need to pull the code with EFI live and go from there. it can be a mulituded of things. running 37s and 4.56 gears will almost automatically throw a ABS code and kill it causing all the lights to come on and ABS to be inoperative. even on a stock tune it will throw a abs code. EFI Live cant fix that issue as it can not flash the new 4.56 gear ratio into the ABS modual so it still thinks you are runnin 3.73 gears when your not. also, adjsuting the speed calculator for anything over 34.5" tires will throw a ABS code for the same reason as i stated for the gears. your goin to need a tech 2 to do the job you need IF this is your problem. But your goin to need to pull the code its throwing to verify what the issue is.

As for the bully dog, i dont know if they can flash into the ABS modual to make things correct and keep the light off

read this thread as well. http://www.duramaxdiesels.com/forum/showthread.php?t=944

AGAIN, BEFORE YOU TAKE MY ADVICE, PULL THE CODE TO VERFY THE ISSUE.

 

[zfuller123]

Thank you for the advice. The code has been something along the lines of the wheel speed sensor code... same one i've seen in other trucks when we start honing in the bigger tires. I will have him pull it again as it is usually 2 or 3 codes on all the trucks i've seen it happen on, but - let me start that again. I dismissed it as the 'norm' that usually crops up when starting to mess with tire sizes in EFI....

From my reading on here, i have tried tire sizes from about 30" to 34". I should have stated that originally. I'll try to get the codes and report back on that first, and if they're actually out of the norm that could be a good indicator. I think we're still going to try putting the bullydog back on, setting tire size, and seeing if the light goes away too. Since the truck is about 4 states away - it's a process

Also, i have left gearing alone at 3.73.

 

[Chevy1925]

Thank you for the advice. The code has been something along the lines of the wheel speed sensor code... same one i've seen in other trucks when we start honing in the bigger tires. I will have him pull it again as it is usually 2 or 3 codes on all the trucks i've seen it happen on, but - let me start that again. I dismissed it as the 'norm' that usually crops up when starting to mess with tire sizes in EFI....

From my reading on here, i have tried tire sizes from about 30" to 34". I should have stated that originally. I'll try to get the codes and report back on that first, and if they're actually out of the norm that could be a good indicator. I think we're still going to try putting the bullydog back on, setting tire size, and seeing if the light goes away too. Since the truck is about 4 states away - it's a process

Also, i have left gearing alone at 3.73.

if it has 4.56, it needs to be changed. the computer is seein the rear driveshaft spinning faster than the 3.73s spin and when it compares the front wheel speed vs the rear it sees a prob and kills ABS.Id also try 34.35 for tire size. its the sweet spot for my 37s on my truck and has never thrown a ABS code to date (been over a year now), 34.25 or 34.45 cause the ABS to trip and quit workin on a long road trip

 

[darkness]

if it has 4.56, it needs to be changed. the computer is seein the rear driveshaft spinning faster than the 3.73s spin and when it compares the front wheel speed vs the rear it sees a prob and kills ABS.Id also try 34.35 for tire size. its the sweet spot for my 37s on my truck and has never thrown a ABS code to date (been over a year now), 34.25 or 34.45 cause the ABS to trip and quit workin on a long road trip

you shouldnt have to change the gear size in efi live. i have 4.10's and 35's and left my gear ratio and tire size stock in efi live without any codes and read within 1-2 mph on the highway with gps. i have however had the ABS re-calibrated with a tech ll when i had 3.73's and 33's. 4.56's and 37's are actually closer to stock final drive than the 4.10's and 35's. this is the gear calc i use

 

[Chevy1925]

you shouldnt have to change the gear size in efi live. i have 4.10's and 35's and left my gear ratio and tire size stock in efi live without any codes and read within 1-2 mph on the highway with gps. i have however had the ABS re-calibrated with a tech ll when i had 3.73's and 33's. 4.56's and 37's are actually closer to stock final drive than the 4.10's and 35's. this is the gear calc i use

i know what you mean being the 4.56 w/ 37s are close to stock final drive but the problem lays with the rear speed sensor. It reads off the drive shaft and lower gearing you go, the faster the driveshaft turns regaurdless of tire size. This gives you a different speed than what the front tires read and bam, abs code. You are correct for 4.10 on most trucks as you could get 4.10 factory. But 4.56 is too high for a factory tune, there is no calibration for it in a stock tune so it sees a driveshaft spinning out of range and throws the code.

If you look in efi live at a factory dmax transmission tune with srw and 3.73 gears, the tune actually says you have 4.10 gears in it when really you dont. I need to look back at my stock tune to see if its the same in the ecm but if it is, i think it reads that way for a variable meaning you can go up to a 4.10 and the computer will read it but beyond that, its out of the computers range. This is my theory though lol

 

[darkness]

i know what you mean being the 4.56 w/ 37s are close to stock final drive but the problem lays with the rear speed sensor. It reads off the drive shaft and lower gearing you go, the faster the driveshaft turns regaurdless of tire size.

if you change the gears in proportion to the tires the driveshaft spins the same speed. these numbers are for a 5-speed in overdrive (.75?)
245/75/16 with 3.73 gears = 75 at 2300 rpm <----- stock
315/70/17 with 4.10 gears = 76 at 2300 rpm <------35'' tire
37'' tire with 4.56 gears = 74 at 2300 rpm

the driveline is connected directly to the engine spinning the same rpm +/- 1mph either way. if the driveline was spinning faster the engine would be spinning faster.

 

[Chevy1925]

if you change the gears in proportion to the tires the driveshaft spins the same speed. these numbers are for a 5-speed in overdrive (.75?)
245/75/16 with 3.73 gears = 75 at 2300 rpm <----- stock
315/70/17 with 4.10 gears = 76 at 2300 rpm <------35'' tire
37'' tire with 4.56 gears = 74 at 2300 rpm

the driveline is connected directly to the engine spinning the same rpm +/- 1mph either way. if the driveline was spinning faster the engine would be spinning faster.

I understand that, but you didnt change any gear ratio in the front tires other than tires size. If you make the rear speed sensor see a stock speed but dont make the front ones see a stock speed, its gunna throw the code. Let me put it this way, You essentially slowed the rotation of the front tires but left the rear stock when running 37s and 4.56 gears cause 4.56 gears in the front mean nothing to the abs since the sensor is before any gearing. Only tire size affects the front, not gears and tires. Hope that makes sense.

 

[darkness]

yes that makes sense. so the next question is, how far do you have to drive before you throw an ABS light?

 

[Chevy1925]

yes that makes sense. so the next question is, how far do you have to drive before you throw an ABS light?

with 4.56, not far. 40 miles or less as a rough guess as every truck reacts different it seems. to be honest, Ben (duratothemax) knows a whole heck of alot more on this than me. i know enough for diagnosing an issue but as far as when and how the computer processes it, i couldnt tell ya.

 

[ChevyTruckGuy78]

Thank you for the advice. The code has been something along the lines of the wheel speed sensor code... same one i've seen in other trucks when we start honing in the bigger tires. I will have him pull it again as it is usually 2 or 3 codes on all the trucks i've seen it happen on, but - let me start that again. I dismissed it as the 'norm' that usually crops up when starting to mess with tire sizes in EFI....

From my reading on here, i have tried tire sizes from about 30" to 34". I should have stated that originally. I'll try to get the codes and report back on that first, and if they're actually out of the norm that could be a good indicator. I think we're still going to try putting the bullydog back on, setting tire size, and seeing if the light goes away too. Since the truck is about 4 states away - it's a process

Also, i have left gearing alone at 3.73.

my 02 3500 8.1 had a similar problem and saying wheel speed sensor i tried doing sensors that didnt work i tried one bearing and 2 sensors and nuttin till i replaced both bearings and both sensors the bearings wear just the slightest and it screws with the sensor best way is to get 2 bearings with sensors it would have saved me alot of labor

 

[zfuller123]

Thank you guys all for the input. I'll have the codes posted by morning I hope and then from there it sounds like the solution might simply be we gotta get to a Tech2 for him with EFI. I still would like to see if the Bully Dog can get around the code again... But, the whole process of elimination is under way so - i'll report our progress.