pem Posted August 29, 2020 Report Share Posted August 29, 2020 My 2011 Lincoln MKX will not start. The battery is fully charged. Engine does not crank. Starter solenoid does not engage. No dash lights, no turn signals, but headlights are stuck on and cannot be turned off. If ignition button pressed without foot on brake and key FOB present, the cabin fan will run. Power door locks function. Had to be towed home. Had to disconnect negative battery ground cable to turn off headlights. Here is what I've tested: Battery is fully charged: 12.76 V at terminals after overnight charge. Battery was replaced in August 2019; battery analyzer confirms it is good. Battery problem ruled out. There is no voltage drop between battery terminals and connectors. Battery terminal connections ruled out. 12.76 V measured at starter terminals. Connections to starter and chassis ground ruled out. When start button pressed with foot on brake and key FOB present, NO POWER is delivered to starter solenoid terminal. Bad starter ruled out. Checked all relevant fuses including these engine compartment fuses: starter motor fuse (#19), VPWR fuses (#67, #68, #69), PCM (#86), run/start relay (#87), PCM (#90). Also checked these passenger compartment fuses: run/accessory relay (#10), PATS/PCM (#18), and ignition switch fuse (#28). No blown fuses. Fuses ruled out. Bench tested starter relay (#13), powertrain control module relay (#66), and run/start relay (#88). All checked out fine. Relays ruled out. Tried to read ODB2 code. ODB2 reader powers up when connected, but communications error received because I cannot turn on ignition. Any suggestions for next steps? Thanks! Quote Link to comment Share on other sites More sharing options...
enigma-2 Posted August 29, 2020 Report Share Posted August 29, 2020 About the only thing I can think of that would have a common denominator between having the lights on all the time and no start condition would be the smart Junction Box. Ever have a cabin leak where the SJB may have been exposed to water causing corrosion? Quote Link to comment Share on other sites More sharing options...
pem Posted August 29, 2020 Author Report Share Posted August 29, 2020 No leaks that I am aware of. If I understand correctly, the smart junction box is the same thing as the body control module (BCM)? Is that correct? This does seem to be either a BCM or perhaps powertrain control module (PCM) issue. Is there any way to narrow it down before replacing one of these? If I replace the BCM, does it need to be programmed (like the PCM), or can I simply swap in a new one? Quote Link to comment Share on other sites More sharing options...
enigma-2 Posted August 30, 2020 Report Share Posted August 30, 2020 (edited) The two faults that you describe may have several interconnections, but the there is a definite commonly in the Smart Junction Box. The SJB is the fuse box located in the cabin. (It's actually a small computer besides being a fuse panel). I wouldn't try replacing modules willy-nilly mainly because of the costs. And would strongly rule out simultaneous failures in both the body control module and power control module at the same time. There is no prescient for this combination of faults in the service manual that I could find. (That was the reason for assuming a common point where the faults converge.) Wish I had something more to offer, but with so many possibilities I'd recommend having a professional mechanic troubleshoot the system failures. Its possible that Ford has something in their "lessons learned" library that goes beyond the service manual. Edited August 30, 2020 by enigma-2 Quote Link to comment Share on other sites More sharing options...
pem Posted September 29, 2020 Author Report Share Posted September 29, 2020 (edited) So I ended up taking the vehicle to the dealership. They discovered that wires located under the passenger seat had been damaged over time by the repeated motion of the electric seat. Problem solved by $3 in tape and $500 in labour for diagnostics and installation. :-/ Edited September 29, 2020 by pem Quote Link to comment Share on other sites More sharing options...
enigma-2 Posted September 29, 2020 Report Share Posted September 29, 2020 (edited) Wires under the passenger seat causes no start, headlights stuck on, etc. Incredible! Glad your problem was solved. I imagine a good part of the cost was labor cost for removing and replacing the seat. Edited September 29, 2020 by enigma-2 Quote Link to comment Share on other sites More sharing options...
NOTMY911 Posted September 29, 2020 Report Share Posted September 29, 2020 21 hours ago, pem said: So I ended up taking the vehicle to the dealership. They discovered that wires located under the passenger seat had been damaged over time by the repeated motion of the electric seat. Problem solved by $3 in tape and $500 in labour for diagnostics and installation. ? Different problem but same defect: Recall # 20S37 – Wire Abrasion to Seat Frame. https://ford.oemdtc.com/6582/safety-recall-20s37-wire-abrasion-to-seat-frame-2016-2018-lincoln-mkx-2019-2020-nautilus Quote Link to comment Share on other sites More sharing options...
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