Ok, I am kinda split between here and "wheels and tires" I figure this belongs here because it has to do with the electronics. I am about to order an LBZ. I want to trash the stock tires the instant I get it. However, I would like to correct the speedo. I know the dealer can correct the tire size for ABS.

Does anyone know or has anyone tried the following...

Can you use a LLY programmer to go into the LBZ computer just to change tire size. I am not worried about the performance upgrades yet. Those will come soon enough. Just want to correct the tire size. Has anyone tried this?

:help:

More than likely, no. The 06 trucks use a different data line than the older trucks. To use a Tech 2 on them we must use an interface between the Tech2 and the dash connector to communicate with the PCM. It is called a CANdi module. Also, tuners search your PCM for calibrations that they can modify. If the calibration is newer than the tuner, the tuner won't know what to do with it. You will probably have to wait for an 06 specific tuner.

I wonder how a programmer will work with no CANdi module? I guess they may build something into the tuner.

That was the first thing I thought when I found out the CANdi module was neccessary.. "How the heck are the tuners going to work" LOL

I ran my 03 with 265's since stock till about 30k or so with no recal and I never noticed anything wierd.

Yeah, I am not worried. I just want it all to be calibrated. I guess I am wierd like that.

Bigger tire=slower moving odometer;) not that it really makes a big difference but look on the bright side while you wait for programers to come out:)

Hopefully Edge will be out soon. LBZ runs well, but I need more :horsey:

Max Payne-- Are you positive the 2006's need the CANdi module? You know worlds more about these trucks than I do...but the BCM and everything on the 2006 trucks still runs Class II im pretty sure. A friend just got an 06 LLY and I plugged my Tech 2 in and it worked fine. Read all engine data, trans data, etc... I didnt need a CANdi box. Dont all the Duramax's use some form of CAN for ECM-to-TCM communication? Looking at the pinouts for 2006 and 2005 ECM's and TCM's, it says the 2005 ECMs use a J-1578 CAN data line (I think thats what it was...just off the top of my head) and the 2006's use the new GMLAN. Since GMLAN is a form/variation of the CAN-bus, are they compatible? This was kinda an unanswered question in the problem of getting a 32-bit Gen IV Allison TCM to work with our older pea-brain 16 bit Delphi ECM's. Doing some research, it seems the 2006 Vortec 8100 ECM is UNCHANGED...so wouldnt that mean that older ECM's can still communicate with the newer "GMLAN speaking" Allison TCM's? As I understand it, the two data protocols are compatible, and therefore, should talk to the Tech 2 with no CANdi box. However, the new Caddy's that use GMLAN for everything (no Class II) need the CANdi box because there is no CAN-to-Class II "converter" onboard the truck like it seems there is on the GMT-800 trucks. Our trucks have some kinda converter right? Becuase how would the BCM talk to the CAN-speaking ECM and TCM? Sorry for all the questions!

---Ben

I know that the 06 LLY truck I just had in the shop the other week, I had to use the CANdi to check for codes in the PCM. Would not communicate without it. I will try my truck tomorrow (even though LBZ, should be the same) to verify I wasnt sniffing to many exhaust fumes since the doors of the shop are closed these days :D

thats wierd...cause my Tech 2 worked fine with my friends '06 LLY. Its the latest Tech 2 software and even has the option for selecting "6.6 Liter Diesel --- LBZ" in the "engine selection" screen. Its an OTC Tech 2, not a Vetronix Tech 2 if that makes any difference, with 25.009 updates (latest).

---Ben

we were playing with my lbz back in the shop the other day and we had to use the candi module.without it it the tech2 would not work.

hmm maybe im totally off and seeing things (VERY posible :) )...ill try it again when I go home for thanksgiving.

Yup, CANdi module is neccessary. Trust me, if it wasn't totally neccessary, I wouldn't touch it with a ten foot pole. Piece of garbage rarely works. In fact, it won't allow me to succesfully program the door modules on an 06 for 05 DPF mirrors, so I have to plug the door modules into an 03-05 truck just to program them... CANdi-:t

It must just be for reading engine info...cause im definetly positive I was able to read all BCM/body/chassis outputs and data on my friend's 2006 LLY. Ill take a picture of it when I go home on the 18th.

But why dont we need it for our trucks? They use CAN for ECM and TCM communication...thats what im confused about

Data Link Communications Description and Operation
Circuit Description
The serial data communication among the control modules is performed through multiple serial data communication links. The class 2 serial data line is always present. The high speed GMLAN or controller area network (CAN) may be present for different vehicle options. The data link connector (DLC) allows a scan tool to communicate with the modules on class 2 or high speed GMLAN serial data lines. In order for the scan tool to communicate with the modules on high speed GMLAN link, a CANdi module is needed. The CANdi module behaves as an interface between the scan tool and the high speed GMLAN data link. The CAN is used for functional communication only, among the modules connected to it.

Data Link Connector (DLC)
The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:

Scan tool power battery positive voltage at terminal 16
Scan tool power ground at terminal 4
Common signal ground at terminal 5
Class 2 signal at terminal 2
High speed GMLAN serial data bus (+) at terminal 6
High speed GMLAN serial data bus (-) at terminal 14
Class 2 Serial Data Line
Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. This value is an average, class 2 uses a variable pulse width modulation to carry data and depending on the message it may operate faster or slower. The bus will float at a nominal 7 volts during normal operation. Each module can pull this lower during the transmission. The bus is not at battery positive voltage or ground potential during normal operation. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

The class 2 serial data line on this vehicle is a star configuration. The powertrain control module (PCM) has an additional class 2 serial data circuit to body control module (BCM). If one of the class 2 serial data circuits to the PCM opens, communication will not be interrupted. The following modules communicate on the class 2 serial data line:

The audio amplifier (AMP), w/UQ7 and Y91
The body control module (BCM)
The communication interface module (OnStar®), w/UE1
The digital radio receiver (DRR), w/U2K
The driver door module (DDM)
The electronic brake control module (EBCM)
The generator battery control module (GBCM)
The HVAC control module
The hybrid control module (HCM), w/HP2
The inflatable restraint sensing and diagnostic module (SDM)
The instrument panel cluster (IPC)
The memory seat module (MSM), w/AN3
The passenger door module (PDM)
The powertrain/engine control module (PCM/ECM)
The radio
The rear seat audio (RSA) controller, w/UK6
The rear seat entertainment (RSE) assembly w/U42
The rear wheel steering control module (RWSCM), w/NYS
The remote playback device - CD player (CDX), w/U1S
The transfer case shift control module (TCSCM), w/NP1/NP8
The transmission control module (TCM), w/M74
The class 2 serial data line allows a scan tool to communicate with these modules for testing purposes, checking for DTCs, and to activate/enable/disable functions. These class 2 serial data circuits are bussed together via 2 splice packs:

SP205--Located behind the instrument panel (I/P) near the headlamp switch connector.
SP207--Located in the I/P harness.
Refer to Computer/Integrating Systems Component Views .

Controller Area Network (CAN) Serial Data Line w/6.6L Engine
The controller area network (CAN) serial data line does not communicate with the scan tool via the data link connector (DLC). CAN serial data information is interpreted by the modules that are on the class 2 also, and transmitted to the scan tool. The following modules communicate on the CAN serial data line:

The engine control module (ECM)
The transmission control module (TCM)
The fuel injection control module (FICM)
The glow plug control module (GPCM)
The CAN serial data line, based on J1939 SAE standard, is high speed serial data bus used to communicate information among the modules. Typical data-transmission speeds must be high enough to ensure that the required real-time response is maintained.

The addressing scheme employed with CAN assigns a label to every message, with each message receiving a unique identifier. The identifier classifies the content of the message. Each module processes only those messages whose identifiers are stored in the module's acceptance list. This is CAN's form of message filtering.

The identifier labels both the data content and the priority of the message being sent. Each module can begin transmitting its most important data as soon as the bus is unoccupied. When more than one module starts to transmit simultaneously, the message with the highest priority is assigned first access. A module responds to failure to gain access by automatically switching to receive mode, the module then repeats the transmission attempt as soon as the bus is free again.

High Speed GMLAN Serial Data Line (PHT)
The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data circuit through the CANdi module. The serial data is transmitted on two twisted wires that allow speed up to 500 Kbps. The twisted pair is terminated with two 120-ohm resistors, one is internal to the engine control module (ECM) and the other is internal to the energy storage control module (ESCM). The resistors are used to reduce noise on the high speed GMLAN bus during normal vehicle operation. The high speed GMLAN is a differential bus. The high speed GMLAN serial data bus (+) and high speed GMLAN serial data (-) are driven to opposite extremes from a rest or idle level. The idle level which is approximately 2.5 volts is considered a recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes adds 1 volt to high speed GMLAN serial data bus (+) and subtracts 1 volt from high speed GMLAN serial data bus (-) wire. This dominant state is interpreted as a logic 0. GMLAN network management supports selective start up and is based on virtual networks. A virtual network is a collection of signals started in response to a vehicle event. The starting of a virtual network signifies that a particular aspect of the vehicles's functionality has been requested. A virtual network is supported by virtual devices which represents a collection of signals owned by a single physical device. So, any physical device can have one or more virtual devices. The signal supervision is the process of determining whether an expected signal is being received or not. Failsofting is the ability to substitute a signal with a default value or a default algorithm, in the absence of a valid signal. Some messages are also interpreted as a "heartbeat" of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual device. This code is mapped as a code against the physical device. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

The powertrain control module (PCM) and hybrid control module (HCM) are functionally communicating on both class 2 and high speed GMLAN data links. However the diagnostic communication of the above modules with the scan tool is performed on class 2 data link only. All DTCs set by the high speed GMLAN modules, including HCM, are reported by the PCM on class 2. Data displaying, output controls and programming of the control modules connected to high speed GMLAN only, is performed through high speed GMLAN link.

The GMLAN serial data communications circuit is in a linear topology. The following modules are connected to the link, in order from DLC to the end of the linear configuration:

The energy storage control module (ESCM)
The starter/generator control module (SGCM)
The electro-hydraulic power steering (EHPS)
The hybrid control module (HCM)
The powertrain control module (PCM)

ahhhh ok thanks for that... I understand now...

But I still have one question.

Is the GMLAN of the LBZ/06 LLY ECM/TCM compatible with our older CAN-speaking ECM's? I cant really figure out if GMLAN and J1939 CAN busses are compatible.

I think this discussion got way off topic. Original question involved trying to make the SPEEDO work correctly with different sized tires. I was definitely under the impression that reprogramming had NO EFFECT on the spedometer. It only modifies what the computer sees and the electronic readouts. I know that is the way it worked on my 2003 LB7. Is there a change in 2004,5,6??
Dave

Reprogramming with an aftermarket programmer such as Hypertech of Pred. You can recal the odometer to the proper size on the 2001-2005 trucks.

Nothing out there yet for reprogramming the 06's that I have seen.

So, if I'm understanding this right, the dealer can't correct my speedo for my new tire size?

Alright...I found out for sure...I went out to my truck and instead of selecting "2005" for the modle year with the Tech 2, I selected 2006 and then selected "LBZ diesel". Sure enough, it asked me to connect the CANdi module. Sorry about that guys...I was completely wrong, and I appologize for having a doubt about the need for a CANdi module. What I was thinking of was you dont need the CANdi module to diagnose/read/clear/view data on the BODY or CHASSIS of the new 2006 trucks. However you DO need the CANdi module to look at the engine or transmission.

---ben

What does all of this mean? Can a GM dealership fix the tire size so my 37" wheel combo will be calibrated properly? Or will I need to get a bully dog or something like that?

I will ask the dealership tomorrow when i go for my first free oil change if they can do the tire recalibration, my spedo is like 6mph off at 70mph with my 305 buckshots. i need it fixed asap

No, a GM dealership cannot calibrate for oversize tires. Do a search and you will find all the info you need.

nope, it dont work, guy pluged in his tech 2 but no workie:(

GM has not released codes for larger than a 265, so dealers cannot update. I immediately lobbed a complaint into GM Customer Care -- "an H3 has larger tires", "Ford and Dodge seem to run large tires", . . . My understanding is they are not releasing codes due to Allison issues with oversized tires -- don't know how "oversized" is a 285 or a 35". I've read claims in some boards that dealer went ahead and updated, but I don't see how.

:chevy: Back when I used to work for gm back in 1999 had a truck with a set of tires that was not in the list in the Tech 2. Called gm tech support and they wrote me a special line of code to download for the proper rollout of the tires.
I realize things have changed but I would bet there is someone in tech support that still has this capability.