After reading through dozens (hundreds?) of posts about the Terrain Management System fault, I can now add another potential fix to the problem. Here's the quote from my service invoice: "Multiple codes found. Engine idles rough with terrain management faults. Can hear a vacuum leak. Inspected and found right bank PCV hose disconnected from intake manifold causing faults stored in modules. Reconnected PCV hose. Cleared all faults, performed test drive, codes did not return. Vehicle operates normally at this time."
So here's the definitely not complete list of fixes and attempted fixes for this fault in approximate order of difficulty from least to greatest occurring in Ford Explorer Gen 5 (model years 2011-2019) gathered from threads on this forum:
1. Key cycling.
2. Turned the car off and on again and it was gone.
3. For about 50 to 60 consecutive starts, I have turned the ignition switch to the on position, waited for a couple of seconds, and the Terrain Management System boots up correctly. Then I start the vehicle and it continues to operate correctly.
4. Found Positive Crankcase Ventilation (PCV) valve hose disconnected from intake manifold; reconnected PCV hose, problem solved.
5. Ford Dealership tech was able to review the error codes and actually found a piece of metal/rust in the sensor unit that was causing the fault. All fixed! Took 10 minutes.
6. The terrain management system is dependent on sensors in the wheels that tell the system which are sticking and slipping. When anything (rain, dust, mud, lint, snow, grass, etc...) gets into these sensors it causes the fault. If you have mud or something more permanent in the sensor it will not go away until you take to a hoist and lift up vehicle so that you can pressure wash the back of the tires which is the only way to get at these sensors.
7. The connector to the dial came unplugged and that caused the warning.
8. Went in for an oil change, they reprogramed the abs module and it has yet to return.
9. Dealer replaced the Terrain Management knob twice, and the problem was still not resolved. Software patch had been completed and tested. The patch was to the ABS system apparently to fix the "wake up" order of the various systems. It only took about 20 minutes, and have not had a TMS fault since.
10. Applied the latest sync software and so far no more TMS errors.
11. Apparently the front left ABS wire has been rubbing on something causing it to wear through. Never caught the wear before because the damage was on the backside of the wire. $30 part.
12. Cleared up when the dealer replaced the battery.
13. Dealer found the issue, it was a faulty module in the steering column that was a part of the processing unit for all the traction control systems. They replaced the whole unit, and that has fixed the issue.
14. After what they told me was a lot of back and forth with specialist/engineers at Ford, the dealer decided it to be attributable to a Smart Data Link Module. Since picking it up, I've only driven it a short distance and no light has appeared.
15. My dealer resolved this by replacing a steering angle sensor. The dealer needed several days to diagnose, but once they fixed it, it hasn't reoccurred.
16. This has been a reoccurring problem. I took it back to the dealer and they replaced the steering angle sensor but problem hasn't stopped.
17. An engineer at Ford instructed the service tech to "overlay the harness from PCM connector 175E to ETC connector C204D R, R ETC and PCM cut old wires install new harness on LE134 and RE134 BU/OG, clear all codes and retest." This finally resolved my problems. Thought is that there is some voltage irregularity which is causing a bogus code to be sensed.
18. My Ford Explorer Terrain Management System FAULT was fixed by the dealer after they replaced the ABS Module. It’s been several months, so far so good.
19. It is the throttle body and they replaced it. So easy to malfunction/stuck and it was only around 540 miles on the odometer.
20. Dealer reprogrammed the PSCM (recall) and replaced the throttle body. Of course it is too early to tell if my vehicle is fixed but I initially surmised that these two issues were related, i.e. sometimes the throttle body is stuck just long enough to throw the TMS fault but resumes normal operation before an issue can be perceived.
21. Steering rack has to be replaced.
22. Had a new battery and a brand new power steering rack installed. The new battery fixed the issue for about 3 hours.
23. It appeared that the rear axle had a lazy solenoid and Ford replaced the whole axle. Then the TMS light illuminated again and disabled the knob as it has done in the past.
