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Discussion Starter #1
I have read and done almost all the posts on this problem that I can do. Does anyone have any other suggestions? I have replaced all the stepper motors in dash. All 3 speed sensors have been replaced with brand new one and the ecm was replaced with remanufactured one? Two brand new batteries and still the same problem. Speedo says 85 and the truck will be lucky if it does 40? I have thrown money at this thing left and right and still cannot get it to work any ideas or suggestions would greatly be appreciated. Thanks Eric
 

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Thread moved to Medium Duty Trucks forum.
 

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We need more info on your truck dude.
Is this a new problem?
C4500/5500 have 4 speed sensors, not 3, or at least all 3 of my c5500 have 4.
The more info the better...any abs lights?
 

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Discussion Starter #4
Just bought the truck a few months ago sorry. The guy i bought it from said it ran fine? You all know how that goes. 2003 c4500 6.6 diesel automatic transimission. And if there are four speed sensors I cannot find the fourth? One by bell housing one in middle of tranny and one at tail? That i can see? Just bought the truck to pull back hoe around the farm and haul quads to west virginia four wheeling. And yes I have the abs light on. Do you think that has anything to do with it? Thanks for any help. The spouse is pissed i bought the truck to begin with and now that it does not run she has kicked it into a whole another gear. Thanks for your help.
 

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Speed Calibration

You need to find someone with a Tech2 to reprogram the speed calibration---tire size and differential gears
 

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Discussion Starter #6
When I ordered the ecm for it they ask for the serial number on ecm and the one off the truck that way they could program it for the truck before shipping it they said? When you master say take it to for reprogram is that what they call reflashed? And to put the ecm on I have to turn truck to on wait until security light turns off which is supposed to take about ten minutes and do that three times before even trying to start? Could not find security light on dash or in manual. And now after all that the radio says loc? Which is at this point the least of my worries I think?
 

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Ok, your speed sensors are located at each wheel. There are sensors on the transmission, but from what I recall they monitor transmission input shaft speed and output speed to determine slip and so forth.

Now whats this about new ecm? Why did you figure out on replacement of ecm?

Here is what you need to check. You need to use a scan tool, tech 2, snapon, genesis to monitor wheel speed as you drive. If a speed sensor is out it will show, you should have them all read same data.

Does your chime go off when abs lights come on? Does your speedo eventually drop to zero? I bet your problem lies with your electronic brake control module. See if it is communicating with ecm. Try reading abs codes with scan tool, if it wont read it will throw com error.
I can only speak from personal experience, I had speedo error like yours when I was building my truck and doing 4x4 conversion. Now not sure if 2003 model year was as complex as my 08 but I failed to recalibrate/swap my ebcm. Its the module right by driverside front tire. Somehow the calibration was off between parts truck and mine. Both rear speed sensors were reading different values than front. Front was reading twice as fast as rear and truck had a fit and after few minutes of driving all bells and dingers went off and speedo quit.
Dealer said replace cluster. Swaped one in from other truck, still read way fast. Tried reprograming speedo calibration on efi live to no avail. Swapped ecm and still no fix. Changed speed sensors and nada. Swaped ebcm and voila. Truck been running smooth ever since with accurate speedo. I think it has something to do with reluctor wheel (tone ring inside hub) or speed sensors differences between both trucks. ( there are different styles of sensors available for c4500/5500)
Now, I know radio is vin locked to ecm for theft deterent on my 08. Dealer can reprogram with tech 2 to unlock radio.
Has anybody changed rear end of truck? Or replaced rear/ front rotors when doing brakes inadvertently putting on wrong rotors with missmatched reluctor wheel? (would show up when checking speed sensors so do that first).Or touched ebcm?
Swap in your old ecm and radio should work again. If you somehow have access to another ebcm, truck needs to have same axle gear ratio and drive line (2wd or 4x4) swap and see if it works. It easily unbolts with 4 small bolts on top and lifts off. No brake abs lines to undo.

Sorry for long post. I chased my tail for two months trying to solve my speedo issue. Read hundreds of post with no worky. No one had any answers!

O one more thought....I imagine you checked wiring harness around ebcm for chaffing? Made sure grounding of ebcm was good?...so to recap, start with scan tool first to make sure all speed sensor inputs match, then gomfrom there
 

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Was a solution to this problem ever found?. I have what sounds like the exact same problem. I also have a 2003 Kodiak. Two things were done to the truck when the problem started. I pulled both batteries off the truck and took to town to replace. After I put the batteries back on, I uploaded the EFI tune I had just received. When I tested the truck the speedo reads about 45mph when the truck is doing 20mph, and so on. It won't run over 60 because it is hitting what I think is the speed limiter. Short of taking to dealer, I'm not sure what to do.
 

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I switched the abs computer (exact term escapes me at the moment) from 2wd to 4x4 and that cured my problem. With 4x4 conversion that part was overlooked. Must be different tone rings or programming that caused issue for me. Its the module attached to the abs pump in driver side fender.
 

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Reread older postscafter I replied. Have you tried to load older efi live tune? Does problem remain? Could be rear gear ratio or speedo calibration ( tire size/revolutions) not set correct in tune.
 

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im interested in if anyone ever figured this out my 2004 c4500 2wd has all 3 speed sensors on trans replaced all 4 abs sensors replaced dicks speedo tested cluster found no problems in the instrament cluster i have no codes through but an old freeze fram of u1064 but nothing seems to have bad connections traced back all grounds took dremal and stripped the pain to be 100% on great ground has new fuel filter and trans fluid level is good it still drives goin a max of 41 mph according to the wheel speed sensors read on a tech 2 scan tool but the trans speed shows 81 mph and only shifts through first through 3rd gear unless you let off the gas at 40 mph it wont shift to 4th and cant ever shift to 5th gear at all
 

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Mine had those problems when one of the batteries was bad. Low voltage tried to do the cycle of gauges when key is first turned on. Check both of your batteries.
 

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Both battery are new as well replaced them about a month ago and just did recheck both 900+cca so not battery issue I took to chapman medium duty shop in AZ AS we shall see at to that old post wheel speed sensors or bas sensors read wheel speed the Allison trans has 3 sensors also telling the ecm/Tcm it's speed in order to adjust my trouble is trans is shifting but topping out with gov and the wheel speed sensors are reading correctly at the 40ish mph I'm traveling I'll post once I get results from chapman in order to aid more at another time but thanx for the response
 

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Hey there, i was curious what the end result was to your exact problem im having with my same year and make truck. it all started after the batteries died and it was jump started. now 40ish max with speedo at 85. please any info would be greatly appreciated. big thanks in advance!!!
-J.T. Henry
 
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