Failsafe mode

An issue popped up this week on our 2000 XK8, the weather turned cold (but not freezing) and on both cold mornings so far the failsafe mode came on (with no ODB codes set) after two miles of slow stop and go driving. The failsafe mode dosen't come back on when the car is restarted later in the day. Don't know if it matters but cruise control & fog lights were switched on when this happened.
 
Ideas? suggestions?

next time try not to shut key off when restricted performance light on. Scan it for code while its running, it won't hurt it.
look for a possible p0121 code. Also left side of throttle, unplug tps and see if pins in connector are tin or gold. There is a TSB for that.
if you pm your email address, I will forward the bulletin to you.

Yes cruise control matters. This happened to me a few months back... scared the CRAP out me. After a lot of looking I discovered there is a switch or relay on the break pedal that wears out of spec in some way and when the cruise is left on the cruise and the relay miscommunicate and cause the engine to go into safe mode. I just leave the cruise off unless I am using it and this never happens now.


hope it helps,

ray

Fair point but without knowing his codes, shouldnt be too presumptive with the problem. Many things can cause that light, some more detrimental than others.

Yes, you are right about the codes. Shouldn't assume and I can't swear thats the issue posted. In my case, it seems to be reproducible at will by switching on the cruise but not setting it. Failsafe pops on within five minutes. No codes are thrown thrown though. Funny... I can take a long trip and it never happens with the cruise actually set but drive around with it on and not set and with no exception... failsafe.

If you can scan it while the restricted light is on, there will be a code. If you cycle the key it will clear it. Sounds like a throttle fault.

The intermittent failsafe mode light is coming on again. Posted on this during winter when it was intermittent. It has returned now that it''s summer, and seems to come on consistently.
Symtoms:
after cold start...drive 10 miles or less... stop & go driving with some highway...
Failsafe activates.... leave engine running and connect ODB scan tool... codes are P1111 only... system pass...
Cruise control switch is on, but cruise not activated...
 
Any Ideas where to go/look next??? 

had today intemittent restricted performance .. only on for 15 seconds a day.. then shuts off. lol found kock sensor melted..

LOL Genius,

Remo....unfortunately, a generic hand held scanner may not help you. Dealer may have to scan it with light on. Factory tool accesses alot more than a handheld. At least you can find out what problem is then decide where you want to go with it.

OK, it''s definately related to the cruise control. Left it switched off... and no failsafe mode over three days straight. Is there a separate brake switch for the cruise control? or a related TSB? As for the handheld scanner, mine has record capability and laptop interface, need to study up on it''s capabilities, but I expected the onboard computer to at least set a dynamic performance trouble code with the failsafe light on... but I''m still learning these newer systems, I was trained on the old systems of the 70s, 80s & 90s (before the ODB standard). No doubt you dealer techs have top of the line laptop scanners well beyond what the public can get (drool, drool). Don''t mind getting a dealer to scan it, but that''s a four hour round trip drive... not to mention my wife will question why I keep wanting to buy more cool tools... Any advice will be apreciated.

BTW, checked the throttle body pins, all gold...
 
2nd week now, cruise control switch off, no failsafe.
 
Is there a TSB on this?

15 weeks straight and no failsafe if we leave the cruise control button off until cruise is needed. It has to be related to the cruise button being on during startup...