GoBucks62

I saw several threads related to code P1780/neutral safety switch malfunction, but none with quite the same symptoms I’m seeing with my 1998 ES300. I’ve gotten the P1780 code as the only registered fault, cleared it a couple of times just to see what happens, and it does come back, so there’s that to address. But, in addition, the backup lights do not function at all, and the backup lights, license plate lights, and rear side marker lights do not function if the headlights are on. All other lights seem to be OK with headlights on or off. In addition, with headlights on, the reverse gear indicator shows on the dash if the ignition is off, and reverse and park both illuminate if ignition is on (with the transmission in Park in both cases). The car still runs perfectly, and I’m certainly not going to get rid of it over a $200 switch I can easily install myself if that will solve my problem, but I don’t think it would be worth investing in a bunch of exploratory surgery for a 20 year old car with 215,000 miles if this is a symptom of a larger problem.

Other possible factors: about 3 months ago, the #2 upstream O2 sensor went out, which I replaced myself without issue. The car also has an aftermarket stereo and backup camera that I installed several years ago without issue. The backup camera taps the reverse lights, and the same +12 V tap sends a trigger to the head unit for the camera display to pop up. As this is the only thing not stock on the car, I did disconnect the camera and trigger connections on the chance that I had a short or bad ground in that setup, but symptoms were unaffected.

Any ideas out there? Anyone else seen this when the neutral safety switch fails?