I bought my 720S thinking the worst I would deal with was expensive gas. Wrong.
Three years and several thousand miles later, I have opinions about what breaks, what does not, and what McLaren should have gotten right from the factory. This page is where those opinions live. Not the sanitized known-issues list from a press release — the stuff that actually shows up on owner forums at 2am when someone has a warning light they cannot identify.
Every problem below includes how I diagnosed it, what the SIS says to do about it, and where I disagreed with the factory procedure. Links go straight to the relevant service manual pages in the SIS browser.
This is the number one reason 720S owners call their dealer. The message appears, your heart stops, and suddenly you are Googling whether your car is about to explode.
It almost never is.
The Service Brake System message is a catch-all. It fires for anything from your front pads being worn (normal maintenance) to an ABS sensor sending garbage data. The problem is that McLaren does not tell you which one. You just get the vague warning and a bill if you do not know how to read codes.
What I do when it comes on:
Plug in MDS. Read the DTCs in the Chassis module. The code tells you exactly which subsystem is complaining. Front pad wear sensor? Fine, schedule a pad change. Wheel speed sensor fault at rear right? Probably dirt or moisture on the sensor tip — clean it and clear the code. Brake fluid level low? Top it off with DOT 4 LFV-spec fluid and figure out why it dropped.
The one time this message actually meant something serious was when a brake pressure sensor developed calibration drift. Took me two days to track down because the DTC was intermittent. Lesson learned: if the code comes back after clearing it three times, stop guessing and pull the SIS procedure for that specific sensor.
Related SIS procedures: See the Brake System section in the service manual for pad replacement, sensor testing, and fluid exchange.
The 720S electrical architecture is aggressive. Telematics, keyless entry, parking sensors, infotainment — all of it stays alive when the car is off. McLaren says the parasitic draw is fine. In practice, leave the car for three weeks without a maintainer and you are pushing your luck.
I learned this the hard way. Left for a conference, came back to a dead battery. The replacement had to be AGM (part number MLB-100 or equivalent) — putting in a regular flooded battery will not work with the start-stop system and regenerative charging profile.
What actually works:
If there is one thing every 720S owner agrees on, it is that the infotainment system is a chore. Screen freezes. Bluetooth drops in loops. Apple CarPlay disconnects at random. The whole unit goes black and you feel like you are driving a very expensive brick.
The fix is usually embarrassingly simple: restart the unit by holding the power button for 10 seconds. If that does not work, check the firmware version in Settings then System Info. McLaren has pushed several updates that address specific glitch patterns, and if you are running anything older than the 2024 releases, update first before tearing into wiring.
I had a persistent Bluetooth disconnection issue that turned out to be a software conflict between the phone book sync and the telematics module. Factory procedure said replace the head unit. I updated the firmware instead. Saved $3,000.
The Proactive Chassis Control system uses four individual damper sensors. When one fails, you get a warning that ranges from mildly annoying to deeply concerning depending on which light comes on.
Most PCC warnings I have seen trace back to moisture getting into a damper sensor connector — especially if your car gets washed with high-pressure water regularly. The fix is often as simple as drying out the connector and applying dielectric grease. But you need MDS to confirm which corner is complaining before you start disconnecting things.
Do not ignore this one. A failed damper sensor can put the suspension in a fallback mode that is safe but miserable to drive. Fix it promptly.
The M840T V6 is generally reliable, but some owners report burning more oil than McLaren admits to. The factory spec is up to 0.5L per 1,000 km which is generous language for you need to check your level regularly.
I check my oil every other fuel stop. Not because I am paranoid — because the M840T runs hot under hard driving and the consumption rate increases with temperature. If you track the car or drive it aggressively, check weekly.
If consumption jumps suddenly (more than a quart between normal checks), the first thing to investigate is the PCV system. A stuck PCV valve causes crankcase pressure buildup that pushes oil past the piston rings. Cheaper to replace a PCV valve than to pull a turbo.
Rear differential noise: Some 720S cars develop a whine from the rear LSD under acceleration. Usually means the differential oil is past its change interval. The SIS specifies 75W-90 GL-5. Change it every 30,000 miles regardless of what the maintenance schedule says.
Clutch shudder on cold starts: The 7-speed SSG dual-clutch transmission can shudder briefly when cold. If it goes away after a few minutes of driving, it is normal. If it persists, the clutch modules may need adaptation via MDS.
Water in the footwell: Check the sunroof drain tubes. They clog surprisingly easily and water finds its way into the rear package tray area. Not a dramatic failure, but mold in your carpet is worse than any warning light.
Most of these problems are not catastrophic. The 720S is a well-engineered car that breaks in predictable ways if you pay attention to it. The factory SIS tells you how to fix everything — the problem is knowing which procedure to look up when a warning light comes on at 6pm on a Friday.
That is what this page is for. Cross-reference the symptom, follow the link to the SIS procedure, and you can usually handle it yourself or at least have an informed conversation with whoever is fixing it for you.
More targeted guides: reading DTCs, maintenance schedule, fluid specifications.