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The failsafe light can come on for a few reasons. It may be an electronic throttle or brake switch issue. I recommend that you go to your local autozone or parts store to have the stored codes read from the ECM as they will usually do this at no charge. Once you have the code numbers let me know what they are. Since you just had work done check to make sure that the air tube is still connected properly and the air flow meter is connected.
Here are the codes the mechanic ran last week on my XJ8 (the check engine light was on and it was running rough, especially while idling)
P0308, P0316, P111 and P1643
The complete list of work done is:
Replace 8 spark plugs
Replace 2 ignition coils ( #6 and #8 cylinders)
Replace valve cover gasket (2)
Replace park plug grommet (2)
BTW, the fail safe mode light didn't come on when I drove to the grocery store yesterday afternoon. We'll see what happens today.
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