XJ XJ8 / XJR ( X308 ) 1997 - 2003

Trans too Hot/Failsafe Mode

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Old 08-29-2016, 09:55 AM
XJDanny's Avatar
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Default Trans too Hot/Failsafe Mode

Hello Friends,

I have had my 2002 XJR give me this message three times in two years. It has 71,000 miles. After the first time, I replaced the trans fluid and thought the problem went away. But looking back, I now realize it's only a problem when it's hot outside.

Here are the specifics:

*It happens only when it's hot outside, like over 90 degrees.
*It has been parked for between 20 minutes to three hours after driving and is sitting in the hot sun.
*The car won't start. It just cranks and I get the "Trans too Hot" message.
*When I put it in neutral, it starts easily. The amber light comes on and the message on the dash rotates between "Trans too Hot" and "Failsafe."
*When I put it in drive, the messages stay on until I begin driving away. They immediately go away and never come back. The car drives normally.

Any advice would be appreciated. Thank you!
 
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Old 08-29-2016, 10:01 AM
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Is the tranny properly filled?

I've had it happen twice. Both times in the rain.
Turn it off, start again message is gone.

In my case I figure it is the connector at the right front
corner of the transmission near the starter that is known
to fail. Easily replaced and cheap from a Mercedes dealer
with the upgraded revised part.
 
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Old 08-29-2016, 08:38 PM
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Originally Posted by plums
Is the tranny properly filled?

I've had it happen twice. Both times in the rain.
Turn it off, start again message is gone.

In my case I figure it is the connector at the right front
corner of the transmission near the starter that is known
to fail. Easily replaced and cheap from a Mercedes dealer
with the upgraded revised part.
Happened to me once, @ 62k, after it had been parked ALL day.

I replaced the connector with a new one. When I took the old one out it was full of trans fluid along with the plug - cleaned the plug out real good, not a problem since.

XJDanny - if your connector is original, that's the problem.
 
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Old 08-29-2016, 09:54 PM
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Thank you both for the advice on the connector. Does the connector have a specific name or number? I've never replaced mine and if it's inexpensive, I'll order one from a Mercedes dealer. I would guess mine is original.
 
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Old 08-29-2016, 10:20 PM
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Don't really know the name but most Merc parts guys are
familiar with the part.

To them, the tranny is a 722.6. Chrysler dealers will also have it
and call the tranny a NAG-1.

Should be $30?

You do need to replace it because a leaking bush lets tranny fluid
climb the wiring harness and soak the TCM. Then you are in for
much more money.

So how come I still have mine? Dunno
 
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