what cause an o/d light to start flashing on a 03 Ford Focus se ? on 2003 Ford Focus

I just got my 03 Ford Focus few wks agao. It was running fine ! But then I drove for a 3hr drive on highway and out of no wheres the o/d light starts to flash. I couldnt stop because I was on the highway, but when I press the od button it stop. But now the car runs strange not as smooth. All the shiftin gear is fine.

Asked by for the 2003 Ford Focus
I have an '04 that's had the same problem except it was shifting hard from 1st to 2nd gear, also the electrical system would cut out and cause what I can describe as a stall. Voltage on alternator checked and found to be within range however the resistance was WAY too high for a low-voltage power system. Replaced entire negative battery wire/clamp and the battery itself. Ran a second ground from the negative battery terminal to the car's frame. Drove the car @ 45mph for 3 min without stopping (may be hard depending on where you live) to let it reset the oxygen sensors and whatnot. ALL problems have ceased. Good luck!
Yes that was my same problem. I brought it to the dealer. They couldnt figure out what was wrong ! Then finally they realize it was ground
2 more answers
ther are trans codes,scan and post so we can adv or seek freee insp from aamco then post findings
One of the first places to start would be with the transmission fluid. Its level, primarily. If the level is ok (test when fluid is hot; usually a 20 minute drive) then further diagnosis or changing the fluid yourself would be the next step.
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