Troubleshooting: The automatic transmission remains in 1st gear while driving, unable to shift to 2nd or higher gears; the automatic transmission can shift to 2nd gear while driving, but cannot shift to 3rd or overdrive.
Troubleshooting:
① Improper adjustment of the throttle cable or throttle position sensor;
② Faulty vehicle speed sensor;
③ Faulty corresponding brake or clutch;
④ Sticking shift valve;
⑤ Faulty gear position switch.