Boot or tailgate will not open: latch, switch or module

A boot that will not open is more than an inconvenience if the spare wheel is inside it. The causes are mostly mechanical or wiring, and several are fixable without parts.

Related: rear wiper and tailgate electrics.

First: is it locked, or is it stuck?

Two different problems.

Locked — the latch is holding because the central locking has not released it. Everything mechanical is fine.

Stuck — the latch has released and the tailgate will not move, or the release is not reaching the latch.

Listen when you press the release. A click from the latch means the electrical side worked and the problem is mechanical. Silence means the release signal is not arriving.

The tailgate wiring loom

The most common electrical cause on a hatchback or estate, and it is worth knowing before spending anything.

Every wire serving the tailgate — latch, rear wiper, heated screen, lights, camera, number plate lamps — passes through a flexible conduit at the hinge. That loom bends every single time the tailgate is opened.

Wires inside it fatigue and break, usually inside the rubber gaiter where nothing is visible.

The signature is multiple tailgate functions failing together or intermittently:

• Boot release stops working.
• Rear wiper stops.
• Heated rear screen fails.
• Number plate lights out.
• Reversing camera lost.

Any two of those together points at the loom, not at two separate components.

The repair is a wiring repair, and it is much cheaper than the parts people replace first.

Other causes

The external release switch

Usually a microswitch behind the handle or in the number plate trim, in the direct path of road spray. Corrosion is normal after several years.

Often replaceable on its own.

The latch actuator

The motor inside the latch that releases it. Wears out, and can also freeze in winter.

Central locking not releasing

If the whole car is misbehaving with locking, the tailgate is one symptom of a wider problem: central locking and key fob faults.

The body control module

Commands the release. Faults here usually affect other functions too: BCM body control module diagnostics.

Low system voltage

Comfort functions are shed first when the battery is low. A boot release that works sometimes is often a battery symptom: P0560 to P0563 system voltage faults.

Ice

The latch mechanism freezes, or the seal freezes to the body. Force in that state tears the seal: de-icing and frozen locks.

Struts, on a hatchback

Gas struts weaken and eventually will not hold the tailgate up. That is not a “will not open” fault, but it is the related one you will meet next, and a tailgate falling on someone is a genuine risk.

Getting in when it will not open

Most vehicles have an emergency release accessible from inside the boot — a lever or a keyhole behind a trim cap in the tailgate.

Find out where yours is before you need it. Fold the rear seats, climb in, and locate it now rather than in a car park with shopping.

Where a key barrel exists, the mechanical key in the fob usually operates it.

Water, and why it makes this worse

Tailgates leak. Perished seals, blocked drains and failed light gaskets let water into the boot area, and that water reaches connectors and modules.

Check the spare wheel well. Standing water there explains a great many rear electrical faults.

Water in the spare wheel well and damp carpet and electrical faults.

In what order

1. Listen for the latch click when pressing the release.
2. Try the key fob, the interior button and the external switch — which work narrows it.
3. Check whether other tailgate functions also failed.
4. Flex the hinge loom gently while someone operates the release.
5. Check system voltage.
6. Locate the emergency release for now, and for future reference.
7. Check the boot for water.

This check needs no workshop — an ELM327 adapter and the free tier of the app cover it. Check system voltage before assuming a module fault. Comfort functions failing intermittently are often the battery reporting itself.