S4 not starting and anti-theft lights are blinking

[LAfranius06]

My girlfriend had a tip-over with her 2002 Monster S4 in a parking lot last week. Nothing dramatic, just one of those slow-motion drops. Since then, the anti-theft light blinks three times and the bike won’t start. She used the red key once and it fired up, but now it’s back to ignoring both keys. I’m wondering if the immobilizer might’ve gotten bumped or shifted near the ignition. Anyone had an issue like this before?

 

[1000spaghetti]

I’m wondering if the immobilizer might’ve gotten bumped or shifted near the ignition.

yeah, that sounds like an immobilizer issue, and the tip over definitely triggered it. The immobilizer antenna is the ring right under the black plastic cover around the ignition barrel. A slow drop often shifts or unseats it just enough to lose the key chip's signal
the easiest fix is to gently remove the ignition cover and check the antenna ring. Make sure it is securely clipped in place and flush against the barrel. Check the wiring harness connection to the dash for any looseness or corrosion. If it's loose, you can sometimes carefully use a tiny drop of silicone or glue to secure it once it's correctly seated

 

[negativeION]

I am also suspecting an immobilizer issue like what @1000spaghetti said.

You might want to try reseating or replacing the antenna ring before moving on to more expensive fixes like ECU work. Good luck!

 

[g0alkeeper]

It possibly started once because the tip over may have put strain on the wiring or moved the antenna a bit. I've read from other posts that in the early S4 models the antenna ring around the ignition is known to be sensitive to bumps or loose connections. a small misalignment can cause the ECU to ignore the key.