Brake lights / Brake switch problem?

[hergest]

I recently found that none of my brake lights were working.

I checked the bulbs and the fuse, all seemed okay. I then noticed that I had fault code 423B (16955), which is "Cruise / Brake Switch (A) Circ Malfunction". I reset the faults to clear the engine management warning dashboard light.

After reading some threads in this forum, I realised I probably had a broken Brake Switch. I got this replaced (Halfords Autocentre did it), and now the brake lights are working fine.

However, the engine management light has come back on, and checking the fault codes again I am still getting 423B.

Could it be that something else is incorrect and this caused the fault in the brake switch?

Some other information. A couple of weeks ago I did a long journey, stopped the car and returned 5 mins later. The car wouldn't start, and I called the AA. The battery was flat. The AA checked the Alternator, and the battery recharged quick. They concluded that the battery was in good condition, and there was no problem with the alternator.

Could it be that there is some short, earthing problem, something to do with brake lights/brake switch that cause the flat battery? Maybe the lights had stuck on and drained the battery? I had Air Con on during the journey (and the cooling fans turn on full speed when air con is on).

Everything currently seems fine now, but I'm a bit worried as the fault code has come back.

Note also that I have had a broken secondary air intake for several years, but it doesn't seem necessary to fix (expensive). I get fault code 419B (16795) - "Sec.Air Inj Sys", so the engine management dash light is permanently on (I check for other codes every so often).

 

[hergest]

However, the engine management light has come back on, and checking the fault codes again I am still getting 423B.

Thinking about this further, perhaps the fault was detected again after I cleared the fault codes, before the brake switch was replaced, but the engine management warning light only comes back on to show recorded faults after a period of time/number of miles? i.e. maybe if I reset the fault codes again, it won't come back again and I'm worrying about nothing.

I'm still confused how I got a flat battery though. Faulty brake switch could cause a flat battery?

 

[mty12345]

Unlikely that it was the brake light switch IMO. A weird one though.

I think you are right about the fault code.... delete it and see if it returns.

 

[hergest]

Done 200 miles, and the warning light hasn't come back on yet. I'm expecting it, as I know I have a fault with my secondary air intake. How long does it take for warning light to come back on after fault codes are reset? I've got MOT on tuesday, and I want the warning to come up so I can reset it before I take it in (any warning light is a failure).