The yellow symbol that looks like a horseshoe or coil spring with an exclamation mark in it is the Tyre Pressure Monitoring System (TPMS) warning — usually a tyre that's low on pressure. If your car has air suspension, an actual coil-spring icon usually means a suspension fault. They look similar but mean very different things.
This one trips people up constantly. Half the cars I see with "this weird light came on" have got a 2psi-low tyre.
The TPMS light explained
By law since 2014, every new car has TPMS. The warning is usually a yellow horseshoe/U-shape with an exclamation mark inside. It comes on when one or more tyres has dropped below about 25% of the recommended pressure. First thing to do: check all four tyre pressures (correct values are on the door pillar or fuel flap) and reset the system per the handbook.
Two types of TPMS
Direct systems use a pressure sensor in each wheel. Indirect systems use the ABS wheel speed sensors and compare how fast each wheel spins (a soft tyre spins faster). Direct systems can have sensor battery failures (5-10 year life) which trigger a fault that won't clear by adjusting pressure — the sensor needs replacing (£40-£90 a corner).
Actual coil-spring (suspension) lights
On cars with air or active suspension (Range Rover, Audi A8, S-Class, some Discovery, big Citroëns), an icon showing a car body with a spring underneath usually means an air suspension fault — leaking airbag, dead compressor, or height-sensor issue. These are not cheap. Get it diagnosed properly before driving long distances; air-sprung cars can drop on one corner unexpectedly.
How to tell them apart
TPMS: usually amber, shape like a horseshoe or tyre cross-section, with an exclamation mark inside. Suspension: usually shows the silhouette of a car body with a spring or arrow under it. If you're not sure, the handbook has every dashboard symbol — or take a photo and most garages can ID it free.
My tyre pressures are fine but the TPMS light is still on — why? — Most likely a dead sensor battery (direct systems) or the system needs resetting after a tyre change. Indirect systems need re-calibrating after any pressure adjustment via the menu in the dash.
Will TPMS light fail my MOT? — Yes, since 2012 — an active TPMS warning on cars first used after January 2012 is an MOT failure.
How long do TPMS sensors last? — 5-10 years typically. The batteries aren't replaceable — the whole sensor is changed. Expect to be replacing them around the time the car is 7-8 years old.
More detail on: What does the yellow coil-spring symbol on my dashboard mean?
The short answer above covers the usual case. Below is the extra detail a UK driver normally needs to act on it — how to narrow the fault down, what it should cost, and when it is worth paying a garage rather than carrying on. This is general guidance from a working mechanic, not a substitute for someone putting your own car on a ramp.
Red, amber or just annoying?
Colour is the fastest triage a driver has. Red means stop somewhere safe and investigate before you drive on — oil pressure, coolant temperature, brake system and charging faults all sit in that group and all of them can turn a cheap repair into a new engine or a crash. Amber means the car has logged a fault and reduced something to protect itself; you can usually drive gently to a garage but not ignore it for a month. A light that flashes rather than glows is almost always more urgent than the same light held steady — a flashing engine light in particular means raw fuel is reaching the catalytic converter and every mile is costing you money.
Get the code before anyone touches it
Any warning light stored in the ECU has a fault code behind it, and that code is the difference between guessing and knowing. A basic reader will pull the engine codes; a full-system tool reaches ABS, airbag, transmission and body modules where a lot of dashboard lights actually come from. Write the codes down before you clear anything, because clearing them wipes the freeze-frame data that shows the conditions when the fault happened.
What Bob would check first
Start with the cheap, common and visible: fluid levels and their condition, tyre pressures and wear pattern, battery voltage and terminal condition, and every connector and vacuum pipe in the area of the fault. A surprising share of electrical gremlins are a corroded earth or a chafed loom, and a surprising share of running faults are an air leak downstream of the sensor doing the complaining. Only after that does anything get unbolted.
When it is worth going to a main dealer
Three situations justify main-dealer money: an open safety recall (free), a live manufacturer warranty or goodwill claim, and coding or programming work that needs manufacturer-level software. Everything else — servicing, brakes, suspension, clutches, cambelts, diagnostics — an experienced independent will do to the same standard for a good deal less, and using an independent does not invalidate your warranty under UK block exemption rules as long as the correct parts and schedule are used.
Safe to keep driving?
Treat anything affecting brakes, steering, tyres, seat belts or visibility as stop-now, no matter how well the car appears to be driving. Overheating and low oil pressure are also stop-now: the damage curve on both is measured in minutes, not miles. Most other faults will let you drive gently to a garage, but if the car is in limp mode, losing fluid, or the fault changes how it steers or stops, get it recovered instead. Recovery is cheaper than a tow plus a new engine.
Get an answer on your own car
If you want this looked at properly for your exact vehicle, send the details and Bob will write back — make, model, engine, mileage, when the fault happens and any codes you have. You get a written reply from a qualified UK mechanic with 32 years on the tools, not a chatbot, and your money back if he cannot help.
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