Lost power in traffic? Get out of the way first
Indicate, ease over and leave the road as soon as it's safe. The car can't accelerate out of trouble in this state. If a red light is on, the temperature gauge is high, or there's steam or a burning smell, switch off and leave it off. Hazard lights on, stand as far from the road as you can, and call roadside assistance if you have it. If anyone is hurt or in danger, call 000.
What is limp mode actually doing?
It's a built-in safety net. RAC says limp mode is triggered when vehicle sensors detect a serious issue, such as excessive temperatures or loads, and it limits engine output to take strain off the engine and transmission. The car gives up its speed so that a fault doesn't become major damage.
You'll usually see a warning light, though not always the same one. NRMA says certain red lights can coincide with limp mode in some modern cars, and an orange engine light means the system has found a fault. In a hybrid or EV, look for a turtle symbol, which RACV says means limited power to protect the battery or drivetrain.
What to do right now
Get somewhere safe
Use what speed you've got to reach a side street, a servo or a car park.
Read the dash
Take a photo of every light that's on. Anything red, or a high temperature gauge, means stay stopped.
Switch off and wait
With the car parked and nothing red showing, RAC says to switch off the ignition, wait for around 30 seconds and start it again. If a faulty sensor set it off, that may clear it.
Give a hot car time
If it happened on a long climb, while towing or on a hot day, RAC says letting it cool with the engine off for approximately 20 minutes may bring it out of limp mode.
Check the oil once it's cool
RAC lists dangerously low engine fluids as a trigger. Use the dipstick the way the owner's manual says, and never open a hot radiator cap.
Make the call
Still in limp mode: stay put and call roadside assistance, or ask for a mobile mechanic. Back to normal: drive gently and go straight to a mechanic.
What usually sets it off
| What you might notice | What's going on | |
|---|---|---|
| Sensor fault | It comes and goes, and often clears on a restart | RAC says a faulty sensor alone can activate it |
| Gearbox fault | Stuck in one gear, harsh changes or slipping | The computer holds a gear to protect the transmission |
| Too hot or too much load | A long climb, towing or a rising temperature gauge | Sensors have seen excessive temperatures or loads |
| Turbo or boost trouble | Power drops under load, sometimes with a whistle | The computer trims power if boost isn't what it expects |
| Blocked diesel filter | Lots of low-speed, stop-start driving and a DPF light | RACQ says without regeneration a diesel can enter a limp home mode |
| Wrong fuel | A car that needs 98 filled with lower octane | RACV says this can trigger warning lights or limp-home modes |
| Battery or electrical issue | A hybrid or EV, sometimes with a turtle symbol | RAC says limp mode in these cars may respond to a battery fault |
Why isn't a restart the fix?
Restarting clears limp mode, not the fault. The computer runs its checks again, and if the problem isn't showing at that moment it lets the car run normally. RAC still recommends having the car professionally checked to find out what triggered it.
Please don't disconnect the battery or clear the codes to make it go away. Those stored codes are the quickest route to an answer.
What will the mechanic do?
They'll read the stored codes from every control unit, not just the engine, because the gearbox, turbo or throttle can each set it off. Then they'll watch live data on a road test to see what the computer was reacting to, and test the part before replacing it.
The job can be as small as a sensor or a split boost hose, or as big as a gearbox repair, so ask what the code was and what they tested. Tell them when it happened: speed, gear, load, weather and anything on the dash. For a diesel, a European car or a hybrid, look for a mechanic who works on those regularly, because the faults and scan tools are more specific.
What you can do, and what's the mechanic's job
You can
- Pull over and photograph the dash.
- Try the restart once, if nothing red is showing.
- Check the oil on a cool engine.
Leave to the mechanic
- Reading codes from the engine, gearbox and other control units.
- Watching live data to find the real cause.
- Repairing gearbox, turbo or diesel filter faults.
If it were our car
If it cleared on a restart and drives normally, we'd send the job today and go straight to the mechanic with that dash photo. If it came straight back, or anything red is on, we wouldn't try to get home. We'd stay parked and ask for roadside assistance or a mobile mechanic. Limp mode is the car looking after itself, so it's worth listening to.