2012 Ford Fusion no start anti theft flashing & OBD II port not working

Series of events:

  1. Replaced radio. Someone had put coins in the CD player and the circuit board was smoking. Maybe devices on the digital bus got damaged? That was 6 weeks ago.
  2. Car will not restart. Theft light is flashing, as if a non chip key were used.
  3. Cluster shows failures of blinds spot system, cross traffic system, and T.P.M. system.
  4. Locksmith comes. His fancy scan tool shows several faults. One is ECU cannot communicate with key security interface thing in the iginiton.
  5. Half a day is spent with youtube and turn the key on and off 8 times in 10 seconds and it will start crap.
  6. battry near dead.
  7. Pan handler comes buy who knows how to “F__k with cars”. Insists on using screw driver to force starter to operate. Says it worked on his Cadillac. I try to tell him that it won’t work on any modern car. You can crank it all night it won’t start. Ok saved me a couple minutes finding out that the battery is dead. Couple $ for effort ok goodbye.
  8. Battery disconnected for a minute to see if that will reset anything and put on charger.
  9. No change in the problem.
  10. My scan tool no longer connects to this car.

I don’t have a wiring diagram yet. I don’t know what modules are connected in parallel with the non operating OBD II port.

Any thoughts?

My thoughts? A tow truck. If the locksmith couldn’t fix it, it needs a mechanic with knowledge of the electrical system for your vehicle. BTW, did you disconnect the CD player?

All of them are connected. That is the definition of a network.

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Start off with a fully charged, healthy battery.

Check all the fuses. You should have constant voltage and ground at the DLC. Does your code reader power up but not communicate, or does it not recognize that it’s plugged in at all?

Obviously one of the CAN networks is down, what were the exact fault codes/definitions as read by the locksmith? If you don’t have that info you’ll need to start at the beginning.

I suspect you have a code reader, not an actual scan tool. If you don’t have a device that’s able to access all the CAN modules on the car you’re not going to get anywhere.

No. MY thought is that the old radio caused damaged to one or more devices on the bus.

I thought some cars had two busses, or some kind of active repeater or retimer between the busses even if they carry the same data. I need a diagram still.

Have you ever tried to access the inside fuse box on a 2012 Fusion? I hope there is some trick to it. I was upside down in pain and could only reach one hand in at attime.

My scan tool only does ENgine and some transmission. No ABS and such.

I’m 6 feet tall and 265lbs and I have yet to run into a fusebox that I’m not able to access and check. There’s no secret, it’s just uncomfortable sometimes.

But ultimately I believe you’re gonna need more equipment and information resources than you currently have access to.


ForScan is a Ford-centric app available for Android phones as well as a more comprehensive software for Windows laptops that connects to all of the networked modules. Allows changes as well. Plus there is a large forum of users.


And it is free. The connection cable or Bluetooth dongle is the only cost… if you have one, no cost.

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First priority is to get all components of the OBD II system working and talking w/each other. This is more of a computer-network problem than a car problem, so will take the sort of electronic tools used to solve computer-network problems. Unless there’s something obvious, like a loose or broken connector, I expect you’ll either need the Ford scan tool. or hire another shop that has that tool to diagnose & fix the car’s OBD II network. .

Note: Hiring another shop to help in this sort of situation doesn’t imply anything negative about your shop. It means you are being smart. Sort of like a bookie who accepts a long-odds bet, then makes the same bet with another bookies to reduce the amount of money he’ll have to pay in the unlikely event the better wins.

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The shop reached 4.5 hours on their $165 flat rate diagnostic fee and they won’t work on it anymore without more payment. They want to trace each wire to the ECM as the next step. Looking for an electronics specialist or to work on it myself even if it is winter at this point.

Seems like pulling an ECM from the junk yard just to see if it connects with the scan tool would be easier. The junk yard has free returns here. I think my scan tool only connects to the ECM. Even if the other modules work it probably won’t connect to them. I don’t know. It doesn’t try to talk to ABS or anything else. Maybe the shop’s scan tool is the same.

The Ford dealer has an opening for an appointment that is weeks away!

This is the problem with modern computer operated cars. If computer fails, and replacement part no longer available from manufacturer, could be no fix is even feasible. This problem isn’t unique to cars, home appliances are the same. If you have a 10+ years old computer operated appliance and computer fails, metals-recycler will likely be hauling appliance away. Even though all the other parts of the appliance remain in working condition.

Tracing the continuity of the wires between the ECM and wherever they go might work, but if unlucky and don’t find problem right away, a heck of a lot of effort. IMO your best bet is to have this assessed at a Ford dealership, or a shop with a lot of Ford expertise that has the Ford Tech 2 scan tool.

Years ago I had a computer memory circuit board that failed, and had to trace out the memory pcb’s wiring. Had to probe each point to point for continuity and that it wasn’t shorting to adjacent wires. Hundreds of them. Getting tired just thinking about it … lol … Eventually I figured out a way to get the computer itself to help me do the test, and then found the problem.

Apparently none of the modules are reachable through the OBD II port. Something must be corrupting or shorting out the bus.

I wonder how many modules will have to be unplugged to stop the issue, or if pulling the associated fuse will work.

The shop said there is a lot of corrosion.

The HS CAN+ circuit between the OBD II port and the upper most connector on the PCM (the thing right behind the battery) seems to be severed. It measures 117 ohms. It’s supposed to be 60 ohms due to termination at each end. I assume the PCM is one of the terminators.

Most of the non driving related modules are on the MS CAN bus. The cluster appears to be a bridge between the HS and MS CAN busses.

Apparently the only legitimate way to obtain a full wiring diagram of the vehicle is to be a Ford dealer? The Haynes manual only has a partial schematic. The airbag, passive anti theft system, and ABS systems aren’t even mentioned in the schematics.

There is data at the OBD II port on the HS CAN +/- lines. The signaling seems good and at the correct voltage. None of the scan tool programs will connect. I even used Forscan and it won’t connect. Does Forscan ONLY connect if the ECM is present, and then access the other modules after connecting? Is there some Ford issue where none of the Ford modules will communicate with Forscan or anything else until they have first established communication with the ECM?

If I could just open a console I could see the data being sent over the bus. But none of the programs let you open the console until connected.

The Haynes repair manual says that fueses are very difficult to access due to the location! So it’s not just me! There is a small panel on the left side of the dash that opens though. I can see the right side of the fuses through there. I was able to remove the whole fuse box and lower it somewhat. I did break the plastic things on the top part.

A complete CAN network has 2 120ohm resistors in a parallel circuit. So an intact circuit should be 60ohms. You have either a wiring issue or an open circuit in a module somewhere. Find a wiring diagram and read it as a road map, following the current until you find the fault.

Nonsense. Anyone can purchase a complete wiring diagram from a number of sources. From Ford if you have to, but there are lots of resources like Alldata, ProDemand, etc. My personal opinion of Haynes manuals? I wouldn’t pee on one if it was on fire.


Thanks for the visual :wink:

OP could probably obtain wiring diagram info by short-term subscription to service data provider like All Data or Mitchells. A short term subscription for a single make/model/year isn’t overly expensive.

It seems like the way to approach that problem is the same as you’d approach a dysfunctional home computer ethernet network, say two computers with a 2 printers and a fax machine. Start by testing if computer number one will connect to the printer number 1. Then if it will connect to printer number 2. Eventually you’d find where the problem connection was.

Folks here seem pretty opinionated on aftermarket repair manuals … lol … Both Haynes & Chilton’s did a pretty good job for my 30 year old Corolla and 50 year old truck; The Corolla’s wiring diagram in the FSM is over 100 pages, so quite a bit is left out on the aftermarket manuals. But they publish diagrams for the most likely failure areas. Not to say the aftermarket repair manuals are perfect. One of those manuals claims the rear drum brake self adjuster mechanism is activated by backing up, which isn’t the case. Pulling on the parking brake handle does that. The main problem with aftermarket manuals for current cars, they are like rolling computers. And each model and model year are often quite different. Since a publisher like Haynes must produce repair manuals which cover a range of models and model years to make the publication affordable, it is no wonder a Haynes wiring diagram might prove bogus.

The Mitchells eautorepair.net DIY site seems reasonable! Thanks. Trying to search brings up pages and pages full of spam search results.

After 14 hours of working on this, I have narrowed it down to a connection problem in the HS CAN bus that is routed down to the steering rack where there is a splice that goes to the electric power steering. I assume there is a maximum length requirement for wires that splice off the CAN bus, which is why the whole bus is routed near to the device. It then splices off to the device and the rest of the bus turns around. The wires are the same color so it is impossible to tell which pair is the source and return from the colors.

The OBDII port is supposedly connected to both the HS CAN bus and the MS CAN bus. Using my ELM327 v1.4, it won’t connect to anything even with Forscan with the PCU out of the HS CAN bus circuit. It must not even attempt to connect to the MS CAN bus. There may also be a dedicated diagnostic wire going to the PCU from the OBD II port used to read codes from the PCU in the event of an HS CAN bus failure. This may be how the locksmith was able to read the codes. The full diagrams sure were helpful. The software for the ELM327 must not configure it correctly for these alternate modes, or the hardware doesn’t support it on the right pins.

The Smart Battery Junction (inside fuse box) sure is made so that the plastic mounts break off if you try to remove it, aside from being very difficult to access. I used super glue and JB weld on the back where plastic should have been. It should be stronger now.

Sounds like you’re engaged in a bit of a project there! Suggest to not panic, just take it one step at a time. You always have the option to purchase the needed wiring diagram info. Nothing says you can’t visit a Ford dealership when they aren’t busy, and try to beg the info from them either. Dealership staff folk have a hard timing turning down donuts :wink:

Some years ago I had a similar sort of problem, my otherwise reliable Corolla decided it wouldn’t charge the battery, for no apparent reason. Battery tested good, alternator tested good. Turned out the battery was leaking just a little, and over time the battery acid decanted down the positive cable and right into the wiring harness. Probably took months, even years, but eventually acid got a wire splice and ate it. Charging wire from alternator to battery no longer connected. Took a long time to deconstruct that part of the wiring harness to find the problematic connection. And since it was a high current wire, I had to purchase a special high power soldering iron to re-solder the junction. Just to make things a little more of a challenge, the brake warning light on dashboard was on in addition to to the charging system warning light. Turns out Toyota did that on purpose, so if the charging system warning light bulb is kaput, driver is still alerted service is needed immediately. So when charging system got fixed, brake warning light went out too.