Hold on before replacing the third sensor—check if the wiring harness connector on the new oxygen sensor has backed-out pins, a common issue with Land Rovers. Let me know if the specific trouble codes are P0135 or P0171. If the code is P0141 (rear O2 sensor heater circuit issue), you can refer to my detailed guide: OBD - II Trouble Code P0141: O2 Sensor Heater Circuit Bank 1 Sensor 2 - Causes, Symptoms & Diagnosis

Next time the warning light comes on, don't clear the codes with a diagnostic tool right away. Try to find a place nearby that can read detailed trouble codes. Some auto repair shops do it for free. Most likely, it'll show codes related to supercharging, like P0234 or P0299. Or you can get an entry - level code reader like the ANCEL AD310. It's only around 20 bucks on Amazon. Just plug it into the OBD port and it can quickly read the detailed trouble codes. It's one of the things I always keep in my car. For your situation, I suggest you check if the turbo pipes are loose or leaking air, especially the connections at the intercooler. If the clip on the intercooler joint is loose, it might be okay at low speeds, but it could leak when you're driving on the highway.

First off, check if your OBD port is actually getting power. Grab a multimeter and test the voltage at pin 16. IIf you don’t have one handy, an ANCEL scanner with live voltage monitoring works too—just plug it in, and it’ll show the OBD voltage right away. I’m using the X7 scanner myself,

they probably thought you were talking about the AC clutch. The 2nd Clutch Pressure Switch is actually a sensor in your automatic transmission. That P1738 code is 100% a transmission prob – better hit up a transmission specialty shop.

I paid $500 to replace the compressor, only to find out it was just a loose connector on the condenser fan…

Seems like this isn't really related to the heater core. Back when I bypassed the heater core on my old Cherokee, the AC blew freezing air but the Jeep still ran fine. The real issue here is why your rig's overheating like crazy. Your problem sounds more like the cooling system isn't circulating properly. Check if the water pump's actually working—after starting the engine, feel the temperature difference between the top and bottom hoses of the radiator. If you've got an infrared thermometer, scan the hoses for temperature changes. Don't force it to run like this.

I've encountered a similar situation before, and it turned out that the brake booster was leaking air. You can try stepping on the brake pedal several times when the car is cold - started, and then hold the pedal down while starting the engine. Under normal circumstances, the pedal will sink a little bit. If it doesn't move at all or sinks all the way to the bottom, there's a high chance that the brake booster is broken.

The brake booster and the vacuum pump aren't the same thing. But the car needs them to work together for normal braking. That "brake booster vacuum pump" you mentioned, in some cars, to save space and make things more convenient, they combine these two into one part. Since the BMW repair shop said there's an oil leak at the seals of the brake booster pump, it's likely that the seals in this combined part or those related small components are worn out. I suggest you get it fixed as soon as possible. Otherwise, it might mess up your brakes.

It might be because it's been used for too long and the battery is running low. My Corolla had the same problem before.