Symptoms
- Check engine light on
- Car accelerates very slowly or won't go past a certain speed
- May feel like the transmission is stuck in one gear
- Sometimes a 'reduced power' or 'check powertrain' message appears
Likely causes
- CommonThrottle body or accelerator pedal sensor faultThe computer limits power when it can't trust the throttle signal.
- PossibleTurbocharger boost or sensor issueCommon on turbocharged engines when boost pressure is out of range.
- PossibleTransmission overheating or faultSome transmissions trigger limp mode to protect themselves from further wear.
- PossibleWiring or connector problemA loose connector can mimic a sensor failure.
- Less commonSerious engine mechanical issueLow compression or major component failure can also trigger this.
What to do
- Pull over safely as soon as possible; do not force acceleration.
- Turn the car off, wait about a minute, then restart it to see if the mode clears.
- Check the dash for any additional warning messages besides the check engine light.
- Avoid highway driving or merging into fast traffic until power returns to normal.
- Have the code read as soon as possible; limp mode codes point directly to the failed system.
- If restarting doesn't help, have the car towed rather than driving it long distances underpowered.
- Get the underlying sensor, wiring, or mechanical issue repaired rather than just clearing the code.
- Avoid repeated hard driving until the fix is confirmed, since limp mode is protecting a real problem.
When to call a pro
See a mechanic promptly; limp mode is the car protecting itself and shouldn't be ignored or driven through for long.
Safety
Use caution
Reduced power at highway speed can be dangerous in traffic; move to the shoulder carefully and use hazard lights.