My Engine Fail Safe Light comes on after less than 2 miles and at about the same time every time. However, the car still runs normally with the exception of some functions like cruise control not working. My theory is a bad connection at the throttle body? Has anyone else ever dealt with this. I thought I would ask before I started taking things apart. Thanks in advance for any advice or past experiences.

 

Welcome to the forum. What make/model car do you have? Taking things apart can be an expensive way to solve problems. Stop at an auto parts store and ask them to read the codes, then report the codes here, or get a code reader, either one that works through a cell phone or a stand alone.

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If you have an earlier car, mine's a 98, the cruise control is managed by vacuum to throttle assembly. If vacuum pipe comes loose, this happens and resets until your ccontrol asks for throttle on next hill. But we need the year please.

John

 

I have a 2000 XK 8 coupe. Codes have been checked twice and there are none. As to the cruise control the light on the on/off switch goes off the instant the Fail Safe light comes on. Again, the Fail Safe Mode light comes on but there is no loss of power or performance. This is why I am thinking it is possibly a faulty connection?

 

Hmm, are these the symptoms of a bad brake switch on the older cars? The brake switch is a pair of actual switches, one Normally Open, the other Normally Closed, both on the same cam. If the switches are not always in opposition (as seen by the ECU), some form of error occurs, and I believe the 4.0 cars give these errors. FWIW, failed brake switches are very common. The switch is engaged by a bar off of the brake pedal stem. Sort of a pain to reach and replace. Repairs are also possible with minor soldering. I do not believe these errors are stored, and can only be rear by a Jaguar/LR tool right after they occur (same trip).

 

Thanks fmertz. I was just reading another much older post from an individual that had the same exact issue and it was diagnosed and repaired at a dealership....faulty brake switch. So I will investigate this as well. You mentioned repair by soldering. Any addition input there would be appreciated, three years ago I repaired my ABS module by re-soldering the power plug connection so that is well within my capabilities.

 

You can look around, there are MANY threads of discussion. Basically, the body comes off the bracket and reveals a smallish circuit board with a couple of switches with 3 legs each and a pigtail. Each switch has a lever for activation by the cam. These switches are standard limit switches with both NO and NC (plus common). All it takes is to de-solder these legs and replace the switches. It looks like conventional electronics, nothing too small or hard to work with. I believe there are many brands that can fit the bill here. Start a search on this forum with "OMRON" and go from there. eBay likely has tons of cheap options, too. If you can spare the time, this is the way to go for minimal expense. If not, get a new switch for now, and then repair the old one because the new switch will likely fail too.

 

Trae, you say this happens same place on your trip. Is that up hill? Do you have cc on? That would point to vacuum leak.

tried 2 upload photo not working now. Look for vacuum hose /port on top of throttle body. Ensure connected no leak.

I'll try photo again later.

John

 

Trey8,

How did you do on this one?

John