Why is my bonnet open light on when the bonnet is shut?

Nearly always a corroded or sticking switch in the bonnet catch. It is the most exposed switch on the car, sitting directly behind the grille where it takes road spray and salt all winter. Before blaming it, lift the front edge of the bonnet with your hand — it should not move at all. If it is genuinely latched, clean the catch out and work some light penetrating lubricant into the switch plunger, which frees most of them.

Does a bonnet or boot open warning fail an MOT?

No. There is no MOT defect for the ajar warning lamp or the switch that operates it. The catches themselves are tested: a bonnet that cannot be safely secured in the closed position is a defect, as is a bonnet retaining device that is excessively deteriorated, ineffective or insecure, and a bootlid or tailgate that cannot be secured shut. The tester assesses those by trying the catch by hand, not by reading the dashboard.

Is it safe to drive with the bonnet warning light on?

Check the bonnet before you decide. Lift its front edge — if there is any movement at all, the primary catch has not engaged and the only thing holding it down is the safety catch, which is not designed to take airflow at speed. A bonnet that lifts on a dual carriageway covers the windscreen instantly and you will be driving blind. If the bonnet is solidly latched and the lamp is still on, it is a switch fault and safe to drive.

Why won't my boot open light go out?

The latch switch or the wiring to it. On hatchbacks and estates the loom runs through the flexible section at the tailgate hinge and the wires break there from years of opening and closing, which typically takes the rear wiper, the heated rear screen or the number plate lights out at the same time — a useful clue. On saloons it is more often the switch in the latch itself, which fills with water. Either way it will keep the interior lights on and stop the alarm arming until it is fixed.

Dashboard warning light

Bonnet or boot open light

Last updated 27 July 2026

Quick answer

The car thinks the bonnet or the boot is not properly closed. It is worth taking seriously for a moment even though it is usually a switch fault, because a bonnet that lifts at speed will destroy the windscreen and blind the driver.

What to do: No action needed
Can you drive?: Briefly, gently

Why it is red

Reserved for hazards and for faults where continuing could injure somebody or destroy something expensive. Most red lamps mean stop, though a few mean the opposite, so read the lamp rather than the colour.

What turns it on

A plunger or microswitch in the bonnet catch and the boot latch reports whether each is closed. On the bonnet the switch doubles as part of the alarm's bonnet protection on many cars, which is why a faulty one can also stop the alarm setting.

What to do about it

Stop and check the bonnet physically before assuming it is a switch. Lift the front edge with your hand: it should not move at all. If it lifts even slightly, the primary catch has not engaged and you should not drive.
Reopen and reclose the bonnet properly. Drop it from a few inches rather than pressing it down, so the catch has the momentum to engage fully.
Check the boot and tailgate too, since many cars use one lamp for both and simply show a different part of the car symbol.
If everything is definitely shut, clean and lubricate the catch and its switch. Bonnet catches sit right behind the grille and collect road salt, water and grit all winter.
Have the safety catch checked while you are there. It is the secondary hook that stops a bonnet flying up if the primary catch releases, and a seized or corroded one is a real safety issue that nobody notices until it matters.

Can you keep driving?

Briefly, gently

Only once you have physically checked that the bonnet is properly latched — this is the one dashboard lamp where a thirty-second check at the roadside is genuinely worth doing, because a bonnet that opens at speed covers the windscreen instantly. With the bonnet confirmed shut and the boot closed, a persistent warning is a switch fault and harmless, beyond keeping the interior lights on and stopping the alarm from arming.

What causes it

A bonnet or boot that has not been closed hard enough to latch fully
A corroded or sticking switch in the bonnet catch, the most exposed switch on the car
A worn boot or tailgate latch that no longer reaches its fully closed position
A misaligned striker after bodywork or a minor knock
Water in the switch, which is common on tailgates where the loom passes through the hinge area
A broken wire in the tailgate loom, which usually takes the rear wiper or heated screen with it

Does it fail an MOT?

No.

There is no MOT defect for the bonnet or boot ajar lamp, and none for the switch behind it, so a car will not fail on this warning. The catches are a separate question: a bonnet that cannot be safely secured in the closed position is a defect, so is a bonnet primary retaining device that is excessively deteriorated, ineffective or insecure, and so is a bootlid or tailgate that cannot be secured shut. The tester judges those by hand, by trying the catch, rather than by looking at the dashboard.

Common questions

Why is my bonnet open light on when the bonnet is shut?: Nearly always a corroded or sticking switch in the bonnet catch. It is the most exposed switch on the car, sitting directly behind the grille where it takes road spray and salt all winter. Before blaming it, lift the front edge of the bonnet with your hand — it should not move at all. If it is genuinely latched, clean the catch out and work some light penetrating lubricant into the switch plunger, which frees most of them.
Does a bonnet or boot open warning fail an MOT?: No. There is no MOT defect for the ajar warning lamp or the switch that operates it. The catches themselves are tested: a bonnet that cannot be safely secured in the closed position is a defect, as is a bonnet retaining device that is excessively deteriorated, ineffective or insecure, and a bootlid or tailgate that cannot be secured shut. The tester assesses those by trying the catch by hand, not by reading the dashboard.
Is it safe to drive with the bonnet warning light on?: Check the bonnet before you decide. Lift its front edge — if there is any movement at all, the primary catch has not engaged and the only thing holding it down is the safety catch, which is not designed to take airflow at speed. A bonnet that lifts on a dual carriageway covers the windscreen instantly and you will be driving blind. If the bonnet is solidly latched and the lamp is still on, it is a switch fault and safe to drive.
Why won't my boot open light go out?: The latch switch or the wiring to it. On hatchbacks and estates the loom runs through the flexible section at the tailgate hinge and the wires break there from years of opening and closing, which typically takes the rear wiper, the heated rear screen or the number plate lights out at the same time — a useful clue. On saloons it is more often the switch in the latch itself, which fills with water. Either way it will keep the interior lights on and stop the alarm arming until it is fixed.

This is general guidance, not a diagnosis. Manufacturers draw the same system differently and reuse symbols for more than one function, so check the handbook for your own car before acting on anything here.

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