Changing tire size using Forscan

[holyford86]

I've been attempting to change the tire size and abs reluctor wheel tooth count using forscan and it keeps coming up with an error saying it's an invalid configuration and won't go any further with it. I've tried this with both a J2534 and ELM327 adapters and get the same result. Am I missing something or not doing something right? Truck is a 1998 2.5, manual trans, RABS The speedo was off before I swapped to a 8.8 and that made it even worse, its about 8 mph off at 70. Not sure where to ask this, so here seemed appropriate.

 

[lil_Blue_Ford]

I haven’t tried to mess with that stuff yet, but I’ll probably have to when I get the 00 back up with the 5.0

 

[fastpakr]

I don't think Forscan can make those changes until much newer vehicles.

 

[RonD]

1998 to 2000 Ranger speed calibration is done in the GEM module, not the computer as with 2001-2011 Rangers
1997 and earlier calibration was done with Driven gear in trans/transfercase

Not sure if Forscan can "talk" with GEM module, but that's the module you need to change the Rotations per mile(tire size) number in
There is no ratio calibration needed as the raw speed signal comes from rear ABS sensor, the GEM then converts that 25,000(PPM) signal to the 8,000 pulse per mile(PPM) the Ford speedo, computer and cruise need

Ford used the GEM in Rangers from 1995 thru 2003, but only for Speed calibration 1998-2000

 

[holyford86]

1998 to 2000 Ranger speed calibration is done in the GEM module, not the computer as with 2001-2011 Rangers
1997 and earlier calibration was done with Driven gear in trans/transfercase

Not sure if Forscan can "talk" with GEM module, but that's the module you need to change the Rotations per mile(tire size) number in
There is no ratio calibration needed as the raw speed signal comes from rear ABS sensor, the GEM then converts that 25,000(PPM) signal to the 8,000 pulse per mile(PPM) the Ford speedo, computer and cruise need

Ford used the GEM in Rangers from 1995 thru 2003, but only for Speed calibration 1998-2000

I can access the GEM, it gives me tire size options and tone ring options but errors out when I try to program the changes, not sure why, this is my issue.

 

[RonD]

Have you tried the magic word

I would ask over at the Forscan forum, but it may be unique to just those 3 years for Ranger, Explorers of the same years used the 4WABS module for speed calibration, not sure if any other Fords used the GEM for speed calibration

Key off, pull cab fuse 25 count to 10 and plug it back in, that should reboot the GEM

 

[holyford86]

Have you tried the magic word

I would ask over at the Forscan forum, but it may be unique to just those 3 years for Ranger, Explorers of the same years used the 4WABS module for speed calibration, not sure if any other Fords used the GEM for speed calibration

Key off, pull cab fuse 25 count to 10 and plug it back in, that should reboot the GEM

I will try that and see if I can get any further, if I can't off to the forscan forum I go. Thank you.

 

[holyford86]

Well, it's been a while and I've gotten no where with this, I've tried resetting the gem, I've tried using forscan, I've also tried using the high end scan tool I recently acquired (launch X431pad2) and they both tell me that they're unable to do this. Is there somewhere else I need to go to allow this to be changed? Truck only has RABS so the gem controls speedo. I'm putting in 00108 (8.8) and 00736 (225/70R15) and it just tells me no. Going to see if the old mt2500 brick will do it but I don't have high hopes.

 

[superj]

So that forscan app let's you change the speedo for tire size changes? Wow

 

[holyford86]

So that forscan app let's you change the speedo for tire size changes? Wow

Yes, if you spend the extra few bucks it will allow you to do things like that, my truck just hates me, apparently

 

[fastpakr]

I really don't think Forscan supports doing this until much newer vehicles.

 

[superj]

I wonder what year it starts.

 

[holyford86]

I really don't think Forscan supports doing this until much newer vehicles.

I've researched this, 98 is the first year one was able to do this, this way. By all accounts the process seems to at least very closely mirror the process on the actual ford tool used prior to 2005 (those in the know, please correct me if I'm wrong)

 

[lil_Blue_Ford]

Wonder if the GEM itself might be the problem?

 

[holyford86]

Wonder if the GEM itself might be the problem?

It does all of the things it's supposed to without issue and there are no trouble codes present. It's quite strange