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Thread: Which vehicle / OS to use for instrument cluster

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    Default Which vehicle / OS to use for instrument cluster

    Odd request, but I was wondering which if any of the vehicles have the PCM driving the instrument cluster directly. Specifically, if I did a swap with say a 5.3 out of an 2001 truck (Silverado), does the PCM send the signals directly to the dash? I believe that on many of the vehicles, the PCM signal goes to the BCM ... then to the instrument cluster. I was hoping that certain years / vehicles had a direct path to the dash without having to go through the BCM. The reason for asking is I saw a BMW that had swapped in an LS and he used a Silverado instrument cluster in the Beem'er. I "think" that he might have also used the BCM too. It wasn't listed in his posts. Didn't know of certain setups were a more direct swap than others.

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    I guess a better way to ask is which instrument clusters get their engine data from the Class 2 data? I did a quick look at an 2001 Camaro, and a couple of the gauges gets info from PCM. I also had wiring diagrams for a 2004 Silverado, and it appears as though the gauges on that instrument cluster get their data from Class 2 data. Not sure if the signal comes straight from the PCM into the instrument cluster or if the BCM was involved. Or if stock, it went through the BCM, but in reality for a swap, you could run a wire straight from the PCM into the instrument cluster and have it work.

    One other question would be if I needed a 2003+ setup, did all the LS engines have DBW? I would rather keep a DBC setup, but I don't think there were any DBC's on the 1 MB PCM's. Maybe the van's kept the DBC????

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    On 03+ Your pcm needs an IAC driver in it, and all you have to do is change it in the tune from DBW to DBC. LT1 swap lists what PCMs you can use.

    As for how the info is sent to the dash on what PCMs I don't know the answer to that.

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    Quote Originally Posted by turbo_bu View Post
    I guess a better way to ask is which instrument clusters get their engine data from the Class 2 data? I did a quick look at an 2001 Camaro, and a couple of the gauges gets info from PCM. I also had wiring diagrams for a 2004 Silverado, and it appears as though the gauges on that instrument cluster get their data from Class 2 data. Not sure if the signal comes straight from the PCM into the instrument cluster or if the BCM was involved. Or if stock, it went through the BCM, but in reality for a swap, you could run a wire straight from the PCM into the instrument cluster and have it work.

    One other question would be if I needed a 2003+ setup, did all the LS engines have DBW? I would rather keep a DBC setup, but I don't think there were any DBC's on the 1 MB PCM's. Maybe the van's kept the DBC????
    On GM trucks and SUV's, the tach and speedometer are the only signals that go to the 2003+ clusters over discrete wires from the PCM. Everything else is over Class 2 data. On 99-02 GMT-800 clusters, oil pressure was also a discrete signal wire directly from the sensor, but in 03 oil reading started going over data.

    You dont need the BCM. Class 2 data busses in general (on all GM vehicles that use class 2) dont utilize a central node or gateway. Modules communicate directly with one another as needed; they dont have to first send the message to a master/host.

    IE, the PCM will send everything it needs right to the cluster directly over Class 2.
    2005 Silverado, CC/SB, 4x4, LT, LILLY/Allison
    12.9s @ 108 mph

    many thanks to Ross and Paul

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    Actually, there are a few rare instances where the BCM is needed, and thats on "crossover/transitional" vehicles that still used older Class 2 comms for the body systems, but used newer engine/trans controllers that were GMLAN only. So on those vehicles (the C6 corvette is the only vehicle I can think of that is configured this way), the BCM does act as the gateway/translator between the ECM (which only speaks GMLAN) and the rest of the body (cluster, doors, radio, etc) that only speaks Class 2.
    2005 Silverado, CC/SB, 4x4, LT, LILLY/Allison
    12.9s @ 108 mph

    many thanks to Ross and Paul

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    I believe the TrailBlazer/GMT360 platform was this way as well, 02-05 ones were all Class 2 but 06-09s have CAN/GMLAN for all of the PCM/ECM/TCMs (depending on engine selection). P12 and E67/T42 to communicate on both Class 2 and CAN/GMLAN, everything in the vehicle is Class 2 but ECM<->TCM and to OBDII is CAN.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, starting the mods
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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    Quote Originally Posted by ScarabEpic22 View Post
    I believe the TrailBlazer/GMT360 platform was this way as well, 02-05 ones were all Class 2 but 06-09s have CAN/GMLAN for all of the PCM/ECM/TCMs (depending on engine selection). P12 and E67/T42 to communicate on both Class 2 and CAN/GMLAN, everything in the vehicle is Class 2 but ECM<->TCM and to OBDII is CAN.
    Sort of, but no, the Vette and TB are different scenarios. Yes, you are right, 06+ TB used GMLAN for ECM <--> TCM comms, and for OBD-2 scan tool use. BUT the ECM (E67) communicates directly with the cluster and rest of the body because the E67 has Class 2 DLC chips in it.

    The C6 Vette used an E38, which cant do Class 2. So the Vette relied on the BCM to be the "third party" gateway between GMLAN (ECM) and Class 2 (cluster). Then, once the ECM messages were translated to Class 2 by the BCM, the BCM would forward those messages to the cluster over Class 2.

    TB, the ECM just spoke with the cluster directly, as I said.

    A better comparison would be comparing the 2006-09 TB to the 06-07 LBZ Duramax's....ECM <--> TCM comms is GMLAN, and they communicate with scan tool via GMLAN, but the ECM and TCM are also capable of speaking Class 2, which they did to send data to the body, cluster, BCM, etc.

    Another thing, was that on the Vette, the entire drivetrain was GMLAN...ABS, suspension, etc. So the BCM really did a LOT of GMLAN <---> Class 2 translation. Not so on the TB and LBZ Dmax.
    2005 Silverado, CC/SB, 4x4, LT, LILLY/Allison
    12.9s @ 108 mph

    many thanks to Ross and Paul

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    E67 can do CanBus (GMLAN), Serial Data, or Analog outputs to gauges / IPC ...

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    Guys, thanks so much for sharing all this great information. One thing to follow up on in case anybody else is thinking about this option, the vans did keep the DBC up to 2005. From LT1swap.com

    "What makes things nice, is GM still used a Cable throttle body in the Express Vans with the 4.8/5.3/6.0L engines until 2005 and the GTO in 2004."
    http://www.lt1swap.com/cable_conversion.htm

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    Full-size vans built with a Gen III engine could have been equipped with a cable activated throttle body (DBC) from 2003 to 2006. Only in the final year for the Gen III engine in full-size vans (2007) was the DBC option no longer available.

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