Electrical / HS-CAN issues

Discussion in '3rd Gen - 2007 - 2017' started by Hans Schroeder, Sep 15, 2019.

  1. Hans Schroeder

    Hans Schroeder New Member

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    Dec 31, 2016
    Edmond, OK
    2010 Expedition XLT with 286k miles. It's been a workhorse.
    Driving it about 2 weeks ago on the interstate, not too far from home. Hot day (around 100F), all of a sudden I hear warning beeps and dings from the dash. It flashes something about AdvanceTrac, the wrench icon, etc. The speedometer drops to 0. In a slight panic, I put it in neutral and assess as I coast down the highway. I thought it had died, but realized the RPMs were at idle. Put it back in drive, press the gas petal, no power. Limp off the next exit (about 1/4 mile) and park it at a gas station. I turn it off, let it sit a minute, and start it back up. Same warnings, but it runs. Still no power. I limp it home on the backroads (about 8 miles). Speedometer works intermittently. Once at home, I hook up my old trusty actron scan tool. It shows an error reading (I've used this tool before on it).
    I also notice that when I hook up the scan tool and turn the key on, the dash now shows warning graphics (where the mileage lcd display is) for oil, battery, among others. Those warnings go away if I disconnect the scan tool.
    After some research, I realize a faulty module, sensor, or shorted wire could be causing the issue reading off the DLC.
    As an FYI, the dash was once removed when I flushed the A/C system and replaced the Evaporator and condensor (blown compressor).
    After blindly looking around for a while, I decided to do some voltage leak testing. All relevant grounds and power came back fine.
    I purchased the manual from All Data for the wiring schematics. From there, I started disconnecting modules from the PCM. One of the first, the BCM (or smart junction box) allowed me to connect to the PCM. I plugged that back in and unplugged downstream connections from the BCM. Unplugging one connection with a majority of the wires going down the passenger side running board area allowed me to connect the scanner again. Traced that back to the RCM (Restraint Control Module) under the center console. Unplugging either of the connectors to that allows me to connect to the scanner (one connector has the main power for the RCM, among other connections, the other connector has the HS-CAN connections on it).
    I also purchased an ODBII USB adapter that works with FORScan and has a HS-CAN / MS-CAN switch, as well as FORScan with an extended license.
    I now know more about HS-CAN and MS-CAN than I ever thought I would. It seems that plugging in the RCM disrupts the HS-CAN network. With the RCM unplugged and all DTCs cleared, the Expedition runs normally (without airbags functional of course).
    So am I right in thinking that I just need to buy a pre-owned RCM? I'd buy one from Ford, but they retail for a little over $400. Mine is a AL14-14B321-GB. Some sites I've read seem to indicate that any 14B321 will work, but I can't see that being the case since that model ranges from Mustang to Focus to Explorer to Expedition, etc. Those car models all have different air bags in different locations. I can't find an available RCM with my exact model number, but I would think it wouldn't be too hard to find a 2010 Expedition salvage, even if I have to have it reset if it was in a crash (looking to see if FORScan can do that).
    Are there any services that can test a RCM on a bench? - I'm debating asking a service that will reset the RCM if they can test it.
    Thanks all!
  2. stamp11127

    stamp11127 Super Moderator Staff Member

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    Mar 10, 2012
    Temple, Georgia
    Companies that repair ECMs would be your best bet to repair the one you have.

    I'd go the used version first.
    Hans Schroeder likes this.

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