Limp mode: what it is and what to do

In limp mode, the engine computer limits the power, or the gearbox holds one gear, to protect the car after it has found a fault. It’s meant to get you to safety, not to drive on as normal.

Updated 16 October 2026

What limp mode is

When the engine or gearbox computer finds a fault that could cause damage, or that leaves it unsure what’s happening, it switches to a safe fallback. You may notice:

• Much less power, and the engine won’t rev beyond a certain speed.
• Little or no turbo boost, on turbocharged engines.
• An automatic gearbox that stays in one gear.
• The check engine light or another warning on the dashboard.

Some makes call it emergency mode or reduced power. What exactly is limited depends on the car and the fault.

Common causes

Turbo and boost pressure

Too little boost (P0299) or too much (P0234). On turbocharged engines, a common cause.

Throttle and accelerator pedal

On many cars with an electronic throttle, the engine computer limits power when the throttle and pedal sensors disagree (P2135).

Particulate filter

A diesel particulate filter clogged with soot (P2463).

Gearbox

A gearbox fault, such as slipping (P0730). Generic OBD often only shows the summary code P0700.

Sensors and wiring

A sensor that gives implausible readings, or a damaged wire or connector.

Low voltage

Less often, a weak battery or a charging fault makes control units misbehave (P0562).

What to do

1. Drive gently. Avoid overtaking and fast roads, and use the hazard lights if you’re much slower than the traffic around you.
2. Get to a safe place. If a red warning comes on, such as oil pressure or engine temperature, or the check engine light flashes, stop when it’s safe to do so and switch the engine off.
3. Read the fault codes. Read My Car works with the engine off and the ignition on, and says how urgent each code is.
4. If the car still drives safely, drive gently to a garage. If it doesn’t, or an automatic gearbox slips badly or won’t drive, don’t force it: have it recovered.

Does a restart fix it?

On some cars, switching off and restarting clears limp mode for a while, because the computer checks again from scratch. That doesn’t repair anything: if the fault is still there, limp mode comes back, sometimes straight away. The code usually stays stored.

Don’t keep restarting on the road to get the power back. Clearing the codes doesn’t fix it either.

Finding the cause

The fault code points to the system. The freeze frame shows the conditions it happened in, and live data can show, for example, the intake manifold pressure against the barometric pressure on a turbo engine, on cars that report them.

• P0299: turbo underboost
• P0234: turbo overboost
• P2135: throttle and pedal position sensors disagree
• P2463: particulate filter clogged with soot
• P0700: gearbox control system
• P0730: incorrect gear ratio

Gearbox faults often need a tool for the make: generic OBD shows P0700, and the gearbox module stores the actual fault.

• Freeze frame explained
• Diesel particulate filter (DPF) explained

Questions