Offroad Trailblazers and Envoys

Possible Speedometer and Abs fix for gear change

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by bspellman » Wed Jun 25, 2014 12:14 pm

I was browsing though summit racing's website and spotted this http://m.summitracing.com/parts/jet-50108

Curious if anybody has tried this or if I discovered a possible fix.
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by Eredin » Wed Jun 25, 2014 2:39 pm

Interesting. I just have my Scanguage II adjusted 7% for mine since my stepper gauge on the speedo is broke anyway. You get more information displayed to your preference for about the same money.

http://www.amazon.com/ScanGauge-Automotive-Computer-Customizable-Real-Time/dp/B000AAMY86/ref=sr_1_1?s=automotive&ie=UTF8&qid=1403721506&sr=1-1&keywords=scangauge+ii

Just throwing it out there as an option.
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by Gordinho80 » Wed Jun 25, 2014 6:34 pm

Scanguage doesn't correct what the vehicle's computer is seeing, as this claims to do. It is definitely interesting
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by Eredin » Wed Jun 25, 2014 10:28 pm

Gordinho80 wrote:Scanguage doesn't correct what the vehicle's computer is seeing, as this claims to do. It is definitely interesting


Right. The ScanGuage does this on the back end, within the item itself, taking the PCM reading and adjusting it based on the percentage you input.
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by Trail X » Wed Jun 25, 2014 11:11 pm

Depends on what gears you are switching from/to. It doesn't seem to have enough turns to handle the change from 3.42 to 4.56, but it can handle 3.42 to 4.11.

A possibly better option was posted by Dirty Anton a couple years ago. I have been lookint into it as an option for me.
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by ErikSS » Thu Jun 26, 2014 8:27 am

Which years can't be adjusted with the PCM? Barton told me once but I'm not 100% sure. PCM of NC adjusted my (2008) speedometer without additional charge when they did my Tune.
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by Cable810 » Thu Jun 26, 2014 9:14 am

Wasn't it 06 and up we can correct and any years under we can't. BTW I had to set my scanguage at -13%
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by v7guy » Thu Jun 26, 2014 10:45 am

if you're primarily concerned with the speedo then Anton's method works fine. You can find it here

But if we're having issues with ABS cause the computer doesn't see the right signal, then I would think Antons method wouldn't work as he mentioned when it was hooked up pre PCM he kept getting error codes.
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by Trail X » Thu Jun 26, 2014 2:06 pm

I hadn't remembered reading that, but I trust you. Thats disappointing. I didn't see any warnings against it on their website. I have seen a few things that seem like they would do it, but I guess the ABS system is a bit touchier than the speedometer gauge. I need to read into it more I guess.

I beleive the programming cutoff for speedometer settings is the implementation of the CAN protocols. I think that was 2006+. I don't know if 2006+ can adjust gear ratios.
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by Shdwdrgn » Tue Jul 08, 2014 5:12 pm

2006+ is the cutoff. 2002-2005 used the P10 PCM, which has no aftermarket support for changing the gears (but we do have files available to update to different factory gears). The newer models use the P12 PCM, which does have support in aftermarket programmers to adjust both the gears and tire size.

@Gordinho80 -- I thought you was going to use the HPT file I sent to you to reprogram yours. Whatever happened with that? It seems like programming the PCM with the correct information would be far better than using an aftermarket solution that only mucks with the signals.
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by TBYODA » Tue Jul 08, 2014 7:55 pm

Shdwdrgn wrote:2006+ is the cutoff. 2002-2005 used the P10 PCM, which has no aftermarket support for changing the gears (but we do have files available to update to different factory gears). The newer models use the P12 PCM, which does have support in aftermarket programmers to adjust both the gears and tire size.

@Gordinho80 -- I thought you was going to use the HPT file I sent to you to reprogram yours. Whatever happened with that? It seems like programming the PCM with the correct information would be far better than using an aftermarket solution that only mucks with the signals.

Are the newer 06 & 07 P12's backwards comparable to the older vehicles or could they be adapted? I know the 08+ have also have a TCM which would make it more of a challenge. ;)
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by Shdwdrgn » Tue Jul 08, 2014 9:35 pm

TBYODA wrote:Are the newer 06 & 07 P12's backwards comparable to the older vehicles or could they be adapted? I know the 08+ have also have a TCM which would make it more of a challenge. ;)

Totally different connectors and pinout... although there's been discussion on the other site where a couple people actually rewired a P12 into their older models. If I remember right, one person rewiring new connectors from scratch, and the other person was adapting the whole engine wiring harness (which I believe was the easier route?). I seem to recall there were issues with talking to the BCM, but otherwise I think they were successful? That's just another one of those things where you have to be damn motivated to make it worth the effort.
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by DirtyBacon04 » Thu Jul 10, 2014 10:34 am

Well back to the origin of this thread...
Assuming no one has experience with the item linked in the OP? Is there any reason it wouldn't work for us?
Would it only correct our speedo and not ABS due to the location of our sensors? I have next to nothing knowledge wise about PCM programming.
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by Trail X » Thu Jul 10, 2014 12:34 pm

As I said before, it should be ok for 4.11 gears, but it doesn't seem to have enough adjustment range to adjust for 4.56 gears.

The question is which VSS controls the abs. If someone had a working system, they could try unplugging one of the two and then letting us know which lights come on. Not sure if the speedo uses the VSS as the abs either.
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by TBYODA » Thu Jul 10, 2014 1:42 pm

Trail X wrote:As I said before, it should be ok for 4.11 gears, but it doesn't seem to have enough adjustment range to adjust for 4.56 gears.

Could you use a second one some how, first one adjusts say to 4.11 then second one to 4.56?
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by Trail X » Thu Jul 10, 2014 2:35 pm

You'd have to talk to the manufacturer to answer that one.
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by TBYODA » Thu Jul 10, 2014 2:54 pm

Trail X wrote:You'd have to talk to the manufacturer to answer that one.

:Iagree: Not that I need to use one of these with my 08 :mrgreen: just offering up ideas to others, maybe worthless. :pale:
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by larryk » Thu Jun 09, 2016 9:33 am

Hi guys.... Well, I made the switch (FINALLY) from Trailvoy over to here. Im getting my weinerdog turned into more of a real truck..... I know, not ideal for offroad, but I do want it more capable than what it was.

Soo.....has this issue on a 2004 ever been resolved? I just swapped out the rear axle for a 4.10 (from 3.42) and have the front driveshaft off while Im building up my courage to tackle that front one! I had the PCM reprogrammed, as the original programming was, obviously, way off and it threw the ABS/Brake lights. Got the PCM back, and the trans shifts better, but a)my speedo is still off, and b) after a few miles...damn ABS/Brake light threw down again.

I realize with the 3 channel ABS that the rear input to the ABS comes from the PCM, which is then compared to the front ABS sensor wheel speed. Since the wheel speed is independent of gear/tire size, Im 99% sure the issue is coming from the PCM translating transfer case output shaft speed to wheel speed.....and boom, christmas tree lights on the dash :(

Any help/advice on this is much appreciated

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by tarsh » Thu Jun 09, 2016 9:53 am

I have the swb 4.2 and i as well swapped for a 8.6 rear end with 4.10. In my experience the abs light came from a front hubs Because the wire got pulled on the driver side. My pcm was tuned and i have the 04. So I'm willing to bet it's the hubs abs wire.
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by larryk » Thu Jun 09, 2016 11:06 am

tarsh wrote:I have the swb 4.2 and i as well swapped for a 8.6 rear end with 4.10. In my experience the abs light came from a front hubs Because the wire got pulled on the driver side. My pcm was tuned and i have the 04. So I'm willing to bet it's the hubs abs wire.


Hmmm..... I did absolutely nothing with the front (yet), so Im not sure why this code (and the crazy dash light show) went down when I changed the rear axle ratio. Do you really think that it would be the front hubs?
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