XK8 / XKR ( X100 ) 1996 - 2006

another Failsafe mystery

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Old May 8, 2018 | 10:35 PM
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Default another Failsafe mystery

new battery, always on the battery tender nightly. Charging system typically puts out between 13.5 and 14.1 volts. I have a voltmeter plugged in to the cigarette lighter receptacle and obsessively check the voltage. Car runs great, 120,500 miles.

every 7-14 days, more or less, the car decides not to start in the morning. Failsafe message displayed. No faults shown on my Carsoft LR 1.0

I can run the hard reset procedure, and then the car starts up fine and runs like a champ.

Since the reset is so easy to do, and I can't get any faults to display on the code reader, I'm not really complaining, just curious what's going on.


Z
 
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Old May 10, 2018 | 10:35 AM
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200+ views, and no commentary ??? Not even a "that's weird, too bad, man.... ???


Z
 
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Old May 10, 2018 | 01:48 PM
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It's so unusual no-one may know.

Possibly the CKP.

On some cars as you crank you see low RPM but if CKP fails you see 0 RPM and that's the proof. Don't know if yours does this.
 
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Old May 10, 2018 | 02:39 PM
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Thank you for the input.

So if the tach shows 0 rpm when cranking, check the crankshaft position sensor, right ? I'm guessing this little devil is visible from under the car ?

z
 
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Old May 10, 2018 | 04:21 PM
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Attach your OBDII reader and check your codes if no codes then take your car for a run with your reader connected. Drive that way until you get the Failsafe then pull over and check your reader. My guess is that one of your knock sensors is throwing a temporary code that is not a hard fault.
 
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Old May 10, 2018 | 05:07 PM
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Originally Posted by Gus
Attach your OBDII reader and check your codes if no codes then take your car for a run with your reader connected. Drive that way until you get the Failsafe then pull over and check your reader. My guess is that one of your knock sensors is throwing a temporary code that is not a hard fault.
so far, I've only gotten the FailSafe message after the car has been sitting over night, never while driving, (knock on wood). And then only once every couple of weeks.

As mentioned above, on those occasions when the message pops up, the car won't start until I run the hard reset procedure. After which, all seems normal.

Will report back the next time it happens and any new observations.

thank you.

Z
 
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Old May 11, 2018 | 01:16 AM
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Normally that would be a battery. Maybe your tender has ruined it?
 
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Old May 11, 2018 | 03:32 AM
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Originally Posted by JagV8
Normally that would be a battery. Maybe your tender has ruined it?
so far no evidence the the battery tender + is at fault. After a normal day of driving, the tender takes about 5 minutes low charging to arrive at the "float" or "maintain" function. Battery has been load tested and passed at 100%. Charging system appears to be completely normal.

I might quit using the tender for a month or two to see if that impacts the anomaly .

Z
 
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Old May 11, 2018 | 04:52 AM
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Sometimes places incorrectly load test, checking merely for current.

The car also need the voltage not to sag.

What you describe would be consistent with sagging I think.
 
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Old May 11, 2018 | 02:02 PM
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Originally Posted by JagV8
Sometimes places incorrectly load test, checking merely for current.

The car also need the voltage not to sag.

What you describe would be consistent with sagging I think.

I wish I could put the blame on the 3 month old battery and be done with this perplexing issue. But the battery, a top of the line NAPA battery, is showing no faults, none with load testing of current and not with voltage either. My 50 yrs experience in repair and restoration of classic motorcycles and classic cars may not translate to much in regards to modern vehicles, but battery testing is pretty much thee same as it's been for several decades. I'm confident the fault is lurking in some unknown sensor.

Even when the battery is somewhat depleted by numerous short trips / restarting over and over in one day, I'm having no problems. Only when the car has sat overnight, both on the tender, and off of the tender, then and only then do I get a FaulSafe warning and the subsequent no start, that is, no starting until a hard reset has been performed.

This anomaly is only happening once every 10-14 days, more or less. As mentioned, as long as I have a procedure to get the car going that's laughably easy, I'm not too concerned. Just curious, at this stage.

Z
 
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Old May 11, 2018 | 02:03 PM
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Originally Posted by JagV8
Sometimes places incorrectly load test, checking merely for current.

The car also need the voltage not to sag.

What you describe would be consistent with sagging I think.

I wish I could put the blame on the 3 month old battery and be done with this perplexing issue. But the battery, a top of the line NAPA battery, is showing no faults, none with load testing of current and not with voltage either. My 50 yrs experience in repair and restoration of classic motorcycles and classic cars may not translate to much in regards to modern vehicles, but battery testing is pretty much thee same as it's been for several decades. I'm confident the fault is lurking in some unknown sensor.

Even when the battery is somewhat depleted by numerous short trips / restarting over and over in one day, I'm having no problems. Only when the car has sat overnight, both on the tender, and off of the tender, then and only then do I get a FaulSafe warning and the subsequent no start, that is, no starting until a hard reset has been performed.

This anomaly is only happening once every 10-14 days, more or less. As mentioned, as long as I have a procedure to get the car going that's laughably easy, I'm not too concerned. Just curious, at this stage.

Z
 
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Old May 11, 2018 | 02:35 PM
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I'm out of ideas unless you happen across more data at some future point.
 
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Old May 11, 2018 | 03:19 PM
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sorry for the double posting, don't know what happened ??


Originally Posted by JagV8
I'm out of ideas unless you happen across more data at some future point.

I really appreciate your thinking on this, and you taking the time to post.

I'll keep the code reader in the glove box and hope to catch a fault showing up next time this gremlin surfaces.

Z
 
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Old May 11, 2018 | 07:48 PM
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Then have the OBDII attached to the car before you start it and see if it captures the code.

Originally Posted by zray
so far, I've only gotten the FailSafe message after the car has been sitting over night, never while driving, (knock on wood). And then only once every couple of weeks.

As mentioned above, on those occasions when the message pops up, the car won't start until I run the hard reset procedure. After which, all seems normal.

Will report back the next time it happens and any new observations.

thank you.

Z
 
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Old May 11, 2018 | 08:54 PM
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Thanks for the tip. Will do.

Z
 
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