2001 XK8, 65K

Had an oil change yesterday and needed to replace a headlamp bulb. At my advanced age, I don't do that sort of work myself anymore. I have a good mechanic, but he sometimes hands off simpler jobs to junior staffers.

After driving about a mile from the shop, the failsafe mode & check rear lights indicators started alternating. But, there wasn't any loss of engine power and the rear lights seemed to be working fine.

I've read the threads regarding the "fail safe mode and check rear lights" alert. Some of you say break switch; others says possible dirty throttle body. But let me ask this: Is it possible to mess up either one of those during the course of an oil change and headlamp bulb replacement?

Is this just a strange coincidence or a heavy-handed mechanic?

 

Probably not . . . unless they played the radio through the oil drain period and lowered the battery voltage.

If these go away forget it. If they remain there could be a bulb issue even though it was a headlight bulb.

If they remain I would suggest a reboot of systems by removing the negative battery cable from the battery post and touching the CABLE to the positive post of the battery. That kills all all the low voltage gremlins.

These cars are famous for doing strange things at marginal battery voltage.

 

Thanks. I was ready to do that, but today everything was fine & dandy after driving nearly 10 miles. I'll monitor the situation and check out the battery. Plenty of crank left in it, but the battery is over five years old. Or, the cat might just be acting premenstrual. After all, she is a teenager now.

 

You recharged the battery and temporarily drove the gremlins out of it but they're still in the boot and will be back.
The Soothsayer Sayeth 'New Battery Time'

 

Been away. Sorry for responding so late. Here's the latest. I DID reboot, as suggested. Everything was normal after that -- for about a week's worth of short trips. Then the nonsense began again during a short drive today. Took another short drive later in the day, and all was well again.

As noted, the battery has a lot of crank. I'm not convinced it is weakened by age, even though it is over five years old. However, I've kept the battery on a trickle-charge for 3-4 months each winter for the past five years while I was snow-birding. Might this have had an effect? I have not had the battery evaluated. Should I?

If this anaomaly results from a low voltage situation, what else besides battery and a need to reboot could cause it? If, as several have suggested, this is an indication of a dying brake microswitch, why doesn't it make a difference whether I'm braking or not?

As an aside, I love this forum. I'm learning so much. And I love my Cat. She's so complex. My neighbor owns a cat (the four-legged kind) that craps on her rug whenever she leaves it alone for a few days. Maybe my Cat is merely angry because I don't give her enough attention. Ya think?

 

Anything is possible, I have seen oil cap left off and ruining a couple sensors (you ever try cleaning oil out of an engine compartment), also they could have put their hands on a plastic hose and cracked or broken one or more of them or more likely, they spilled oil on the belt and it was slipping for a while, causing the low voltage problem. Knocked a electrical connector loose and now it is not getting a good connection.
I could go on and on, but I keep getting threats about my ramblings.

 

Just go to one of the parts stors and have the battery load tested. Until you do that everything is just speculation and wasted time.