Why won't my Chevy Cavalier start with the security light on?

Short answer: The Cavalier uses Passlock, GM's anti-theft system. A sensor in the ignition lock cylinder tells the computer the right key turned the switch. If that signal is wrong, the car cranks but won't start, or starts and dies, and the security light stays on. Owners usually get it going with a relearn: key in ON for about 10 minutes until the light goes out, off briefly, then start. If it keeps coming back, the sensor or lock cylinder is failing.

Symptom: You turn the key, the engine cranks (or starts for a second and dies), and the 'Security' light stays on or flashes. It may happen after a battery change, a new lock cylinder, or randomly.

What to check first

1. Watch the security light. Steady or flashing with a no-start points to Passlock rather than fuel or spark.
2. Try the relearn: key to ON (not ACC), engine off, wait about 10 minutes until the security light goes out, turn the key off for about 10 seconds, then start. Owners repeat it up to three times.
3. Check the battery and terminals. Low voltage can upset the system.
4. Note whether it happens over and over. If you need the relearn often, the Passlock sensor in the lock cylinder is likely failing.

Likely causes

1. Passlock sensor in the ignition lock cylinder. The most common cause owners report when the problem keeps coming back.
2. System needs a relearn after a lock cylinder, battery or computer change. The 10-minute key-on wait usually fixes this.
3. Wiring between the column and the computer. Worn wires in the steering column can cause it too.

What it usually costs

The relearn costs nothing. The threads here didn't give shop prices for a Passlock sensor or lock cylinder, so get a written quote.

Is it safe to keep driving?

If it starts after the relearn, it's usually fine to drive, but carry a plan: it can leave you stranded again. A car that starts and then dies in traffic is a safety risk. Verify with a mechanic.

DIY or shop?

DIY for the relearn and battery checks. Replacing the lock cylinder or Passlock sensor is doable for experienced owners but involves the steering column and airbag area, so many people use a shop.

Recalls, bulletins and complaints in plain words

• Related recalls: NHTSA lists these recalls touching this area of the Chevy Cavalier: 04V036000 (2000-2001 model years, electrical system); 08E063000 (2000-2005 model years, steering). Check your VIN at nhtsa.gov/recalls. If your car is part of this recall, the dealer fixes it for free.
• NHTSA complaints: 118 keyword-matched complaints for Chevy Cavalier 2000–2005 (of 2,105 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-23; keywords: security, theft, Passlock, no start, won't start, crank). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Passlock?? 97 Cavalier will not start on ChevroletForum, a 1997 owner had a crank-no-start with the security light on. A member explained the relearn: key in RUN (not ACC) for 10 minutes, off for 10 seconds, and repeat. He said it worked for him after swapping a lock cylinder on a '96.
• In this 2000 Cavalier thread on CR4, an owner's car wouldn't start with the security light on. The advice was to leave the key on for 10–15 minutes until the light goes out, then start it, and members called it a very common Passlock problem.
• In 96 cavalier no start, passlock issues or gauge cluster. please read. on Reddit r/MechanicAdvice, a 1996 Cavalier owner had a no-start and wasn't sure if it was Passlock or the gauge cluster.
• In Chevy Cavalier 2001 - Possible Passlock issue, car will not start. on Reddit r/MechanicAdvice, a 2001 Cavalier owner suspected Passlock when the car wouldn't start.
• In 2002 Chevy Cavalier - Fuel Pump or GM Passlock Preventing Start? on Reddit r/MechanicAdvice, a 2002 Cavalier owner asked whether a fuel pump or Passlock was keeping it from starting.

Quick tip

Try the relearn before you tow it anywhere. If you need it more than once or twice, plan on replacing the Passlock sensor or lock cylinder before it strands you.

Vehicle focus: 1996–2005 Chevrolet Cavalier (and the Pontiac Sunfire) with Passlock. 1995 models and other GM systems may differ.

Safety / mechanic note

A car that starts then stalls can leave you stuck in traffic. Verify with a mechanic.