A few days back, I was driving down from Lungro La — a high mountain pass at 14,266 feet above sea level — after visiting the ever-so-gorgeous Sangestar Lake (better known to most as Madhuri Lake). The road down to Tawang was quiet, the air thin, and the scenery nothing short of surreal. And then, right in the middle of all that beauty, my Hyundai Alcazar decided to throw a curveball at me.

The Check Engine Light (CEL) warning came on!

Now, if you’ve ever been on narrow Himalayan roads, you’d know — it’s not the best place for your car to start showing red and yellow icons you normally only see during ignition. My first reaction was a mix of irritation and worry: “Really? Now?”

High Altitude and Modern Cars – Hyundai Alcazar 1.5T Petrol

Driving at this altitude isn’t just hard on us, it’s hard on the machines too. The air is thinner, there’s less oxygen, and for a turbo-petrol like mine, the engine management system has to work overtime to balance things. Sensors keep feeding data to the ECU, and if anything looks even slightly “out of range,” the car flashes a warning.

Most of the time, it’s not catastrophic. It’s just the car being a little paranoid.

The Pause That Should Have Helped

I pulled over, took a breather, and decided not to panic (I did). After all, the car wasn’t jerking, losing power, or making any funny noises. The light was steady, not flashing. I knew enough to understand that meant “keep calm, but check soon,” not “stop driving right this second.”

I Googled, YouTube-ed and, as per current times, asked ChatGPT as well. All pointed towards an O2 sensor issue due to a lack of Oxygen. And here I thought, such issues were only for old vehicles that had carburetors!

So I let the engine rest while I soaked in the mountain silence. Half an hour later, I restarted. And the Check Engine Light was still there. The good thing, however, was that my Alcazar felt peppier, back to its usual self, humming along as if nothing had ever happend.

Still worried, I resumed my descent to Tawang, the CEL still on!

Finally, all was good

Finally, after reaching Tawang, I went back to my room, took a hot shower, sipped in a few cups of hot Ara and decided to go check the CEL situation. It had been more than an hour now, and I was hoping the CEL warning would be gone.

I hopped into the driver’s seat, pressed the Start / Stop button, and voila! The CEL was gone! Relief 🙂

What Happened Here?

At high altitudes, the ECU sometimes struggles with the air–fuel ratio. Throw in the turbo boost, maybe a not-so-great batch of fuel, and the fact that I had just refueled to the brim, and you’ve got the perfect recipe for the ECU to overthink. It flagged a warning, then later decided everything was fine.

Basically, the car had a little drama moment, and then it was all good again.

Lessons Learned

• Don’t panic at the first sign of a warning light. Steady CEL = usually safe to drive cautiously. Flashing CEL = pull over immediately.
• Give the car a breather. Sometimes, like us, it just needs to catch its breath.
• Altitude does strange things to engines. Especially modern turbocharged ones that are tuned for efficiency.
• Always fuel up wisely. Bad petrol + thin air is not a happy combo.

As I wound my way down to Tawang, I couldn’t help but laugh. Here I was, surrounded by some of the most stunning landscapes in the Eastern Himalayas, and the only “drama” was from a blinking little light on the dash.

Travel, after all, isn’t just about the destination. It’s about these small, unexpected stories that stick with you long after you’ve driven past the last prayer flag.

Tech Corner (for the curious)

• Why did the CEL appear?
  At 14,000+ ft, the air has ~40% less oxygen than at sea level. The ECU, turbocharger, and sensors (like oxygen and MAP) have to constantly adjust. If readings fall outside expected ranges, the ECU triggers a warning.
• Was it serious?
  Since the light was steady and the car drove fine, it was more of a temporary imbalance (fuel-air mix, boost, or even a vapor issue after refueling). A flashing light would’ve been serious.
• Why did it clear?
  Once conditions normalized (engine cooled, ECU recalibrated), the system saw no fault and the light turned off automatically.