JohnTN

I don't know if this has been happening for some time, but I replaced my battery two days ago, and last night someone pointed out my backup lights were on while stopped at a red light with the shifter in neutral.

Testing at home, I shifted through the gears sitting still and backup lights only came on in reverse. Thought everything was okay, but pulled into the garage and my wife said they came on when I applied the brakes. And they stayed on as I shifted through the gears in the garage, until I went into reverse and then back to neutral. At that point they went off and then worked as they should as I shifted through the gears again.

Any ideas? Are the BU lights controlled by a simple switch or through the computer?

John

pascal

Two things that comes to mind is your back up light switch might be going bad.
Or.......... More likely, the computer might need to re-learn the circuitry upon having the battery going dead.

You can try to disconnect the battery for 30 seconds and reconnect to clear the glitches.
Put the car in neutral before doing that (and windows up all the way), just because...
Those modern computer cars can be fickle at times.

157dB

There is no 'relearning' PasCal.
Once the SJB is programmed, its programmed.
Ford Workshop Manual
The back-up lights are controlled by a low voltage board in the SJB.

The shifter (or the tranny in a manual) tells the PCM its in reverse.
The PCM tells the Insturment Cluster over the HS CAN BUSS and
the Insturment Cluster relays this info to the SJB over the MS CAN BUSS.
I would start at the SJB and check it for water damage.
Its a known TSB that tyhe S197s leak water into the passenger
cabin and on top of the SJB causing corrosion and problems like you describe.
Otherwise, check the shift switch (you dont mention manual or AUTO tranny )

JohnTN

Manual tranny. Car has seen very little rain or water since I purchased it used 1.5 years ago. It is garaged and rarely goes out in the rain. I will look for signs of leaks but doubt that is the problem. Will try a battery disconnect.

Thanks
John

pascal

Well, reset was more like the term.
I still would play with the battery, for giggles.


And yes OP, the water issue can make a real mess on those electronics.
Take a look at it and make sure it's dry.

JohnTN

I disconnected the positive battery cable for 25 seconds. Now seems to work correctly: went through all gears in the garage with them lighting only in reverse, then backed out and turned lights on like the situation was last night, pulled into garage and stopped without backup lights coming on, then shifted through all gears again and they only lit up in reverse. Maybe they are "reprogrammed" now.

Thanks