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Video | Here’s Everything That’s Currently Broken on My Cheap McLaren MP4-12C

Not. Even. 48. Hours. That’s all the time I had to enjoy my newly repaired McLaren MP4-12C before I was greeted with the friendly amber glow of the check engine light. I knew this car would be needy, and since it’s a technological wonder with a full warranty still in place, I thought the ownership experience would be worth it — but only 48 hours? Really, McLaren??? Mercifully, though, it turns out I was freaking out over nothing.

I actually have California to thank for not freaking out about my check engine light anymore, since they were the ones to initially mandate a universal onboard diagnostic system across all makes and models sold in California. The U.S. government joined California in making a standardized diagnostic plug a nationwide mandate in 1996 — and ever since, any shop with a hand held scan tool can grab basic engine fault codes on everything from a Firebird to a Ferrari.

Even more than 20 years later, the plug’s dimensions remained unchanged, which is why I’m able to plug in the same scanner I bought for $100 on Amazon to nearly every car in my fleet. Being able to read the codes is sometimes even more frustrating, since sometimes the solution to whatever fault the car is having isn’t obvious from the codes — which, unfortunately, is the case with my McLaren.

Mercifully, my 12C only has one active fault code, and it’s an emissions related code that won’t ever leave me stranded on the side of the road. It says specifically "catalyst system efficiency below threshold bank 1," which basically means the exhaust system on one side isn’t clean enough. If I lived in a state with vehicle inspections, like Texas or California, this fault would prevent me from registering the car — but I’m lucky that Kansas does not require this.

For a used car dealer, which I was in a previous life, this code is a very annoying common occurrence. Catalytic converters, one of the most common culprits for this code, are one of the few parts that are illegal to buy used, and the rare metals used inside of them to convert exhaust gases into less harmful pollution can be very expensive — even on normal cars. On European imports, many of them cost over $1,000, which completely wipes out any hope of profit — but it’s a repair that has to be done, since you can’t expect a retail customer to buy a car with a check engine light.

As for what is causing the fault on my McLaren, it could be a number of things. A catalytic converter can fail due to age, or a poorly running engine can hasten its demise. Since high oil consumption was an issue with my McLaren before the engine is replaced, it could have gummed up the exhaust — but since it’s been nearly 2 years since the engine was replaced, I would imagine if this were the cause, it would have happened much sooner.

Another possible cause, which the McLaren service advisor agreed with me as a good possibility, is the exhaust was loaded up with carbon from being moved around a parking lot for months during the winter in limp mode, a default setting that doesn’t have the car running optimally when something major fails — like the transmission, in my case. If that really is the case, then all I need to do is reset the code and do some spirited driving — which I’m happy to oblige.

It’s also possible that some portion of the exhaust was damaged or not installed properly during the transmission replacement job — but if did have an exhaust leak, I would be hearing it, and any other failing components, like an oxygen sensor, would throw a fault code as well. Still, I wanted to have my mechanic, the Car Wizard, take a peek on the lift just out of curiosity — and I also really wanted to see what this advanced electronically controlled suspension looks like, along with the carbon fiber underbody.

Other than a few other minor cosmetic issues, there’s nothing else to really complain about. The best case scenario is the engine light doesn’t come back as I drive it more — but even if it does, this would all be covered under that sweet, sweet McLaren certified warranty. There are some drawbacks to this warranty, sadly — but I’ll cover that in the next installment to my supercar saga.

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