2008 F450 No Start after Aftermarket Flat Bed Installed
Whenever I go out of town it seems that I come home to a pile of problem vehicles. Among the rif raff from the last two weeks, This one stands out. The truck went in to an upfitter for a flat bed. It drove into the shop just fine. Once on site, it was evident this steed had been rode hard and put away wet. It had had more than one transfer case explosion which damaged a good amount of wiring underneath. I suspected maybe some shorted wires.
The customer told me that they drove in the truck and disconnected batteries because they would be welding on the frame. Once all the welding was done, they tested all their wiring for the lights which worked fine. When they attempted to start the vehicle, there was no start. Then the immo lamp started to flash rapidly. Just in case there was a key issue, I cut a new key and programmed to the vehicle. It programmed fine but still no start.
Once connected with the scan tool I found there was no communication with TCM and PCM. Looking at the communications network, it appeared that if there was a problem with CAN, then it would have effected other modules on the same branch. The customer had already checked fuses. So for the time, I put that on the back burner. I removed the connectors from the PCM and tested the powers and grounds. There was no power coming in several of the required pins. So I knew there was a power issue.
I then went to the PCM relay and jumpered the secondary side. Now I had comms with the TCM but not the PCM. I did more digging and found what I suspect was the original issue. There was an aftermarket security system wired in. I disconnected the system and reconnected the wires that were cut. Still no comms with PCM. I then went back to the fuse box. I found two fuses that were not placed back in the correct sockets. Once placed back where they went, I reinstalled the PCM relay. Now I have comms with PCM and TCM. Immo lamp is off. The vehicle starts and runs. Both keys work.
So here is what I suspect happened. When the battery was removed, it placed the aftermarket system in a theft mode. Without the device to disarm, the vehicle would not start. (the device had long since been lost) My customer (the upfitter) tested the fuses and located them in the wrong spot. Then I came in and removed the alarm system and had to go to the extended effort of correcting the fuse locations. So while diagnosing the problem, the problem itself was compounded. The PCM relay feeds both the PCM and TCM. Without the “hot in run” fuse in place, the relay would not engage. Once restored to stock. It all worked. Happy Motoring!
Based on the headline I was expecting an EGT open causing no crank, but nope you surprised me with owner tampering and aftermarket equipment, two of the most notorious causes of all vehicle issues.
lol at "owner tampering" . Remember that old joke labor rate sign? If you worked on it: + + $$$
Hi Michael, Sounds like you had a bit of a chase. The good part is the customer told you they had been tinkering. Regardless of their good intentions, that always sends up a red flag in my mind. As for aftermarket alarm systems, I have no idea why people still think they actually are any good to have. I have seen experienced people override those things really fast before. It my be a good…
can be?? I'd say "are". 100% :-) We were born to fix things that broke....not things that were sabotaged...LOL
Hi Geoff, Usually the “sabotaged” jobs hit me when I am the 3rd or 4th guy called in to resolve the issue. Sadly, I have had to come in behind many of these situations and put everything back together then start from ground zero. Missing fuses and swapped relays are a very common thing around my area. A customer with a couple of half wit buddies and a six pack (or more) on a weekend can often…
Just another great example when diagnosing any issue to remember to remove aftermarket installed components, then proceed! Thanks for sharing!
Sounds like typical day as a mobile diag guy to me.
Hi Justin, I especially like the ones that start of with the immediate question of “What do think it is, so I can fix it myself"? My answer is a generic, 'I don't know without a diagnostic check over'. All mobile techs have also run into the “lets make a deal” customers after the repairs or diagnostics are done. This can be an interesting sort at times. This usually takes some tactful…
I find at least a couple times a week a job like this comes up. Not always a major diag situation though. Guys that aren’t on the road providing this service don’t seem to understand what we see. Just yesterday I got a call to look at a 2017 Malibu that had an active grill shutter replaced along with the sub harness. it was a damaged part from an impact when a customer hit something. The claim…