The following article gives detailed instructions on replacing the cylinder head temperature sensor in a BMW with the N20 2.0 liter 4 cylinder engine. The N20 engine was used in many BMW models including the 1,2,3,4,5,X and Z vehicles. Even though we have used a 2014 BMW 320i to perform this repair, this article can be applied to any vehicle with the N20 engine with minor modifications.
A BMW N20 cylinder head temperature sensor failure is a known cause of engine power shutdown and the vehicle entering “limp mode”.
There have been reports slowly filtering in from BMW owners of vehicles with the N20 2.0L engine entering “limp mode” while driving for no apparent reason. It usually happens after the engine warms up and while idling at a traffic light or a stop sign. Sometimes a “check engine” light may be displayed…but sometimes it may not.
The 2014 320i that we used for this article started shutting down approximately five minutes into driving with no check engine light and the engine temperature gauge operating correctly. When we turned the engine off and restarted, the vehicle would return to normal operation for a few minutes, only to shut down again. A diagnostic scanner attached to the car revealed a P1290 code, which lead us to believe the cylinder head temperature gauge may be faulty. Replacing the cylinder head temperature gauge immediately cured the issue and the vehicle is back to operating normally.
The BMW N20 cylinder head temperature sensor monitors the engine’s coolant temperature at the top of the engine block. This data is sent to the BMW’s DME (engine control unit) where it is used to manage engine operation and performance. If the sensor reads that the coolant in the cylinder head is too hot the DME will send the engine into “limp mode”, effectively cutting power to the vehicle and avoiding engine overheating.
The issue that is plaguing many BMW owners with the N20 engine is premature failure of the sensor (the 2014 320i that we repaired for this article only had 43,000 miles). BMW N20 cylinder head temperature sensor failure may cause the DME to falsely assume the engine is overheating, forcing the vehicle to cut power and eventually shut down.
Replacing the BMW N20 cylinder head temperature sensor is a very simple procedure, and depending on the model you are working on can take as little as 15 minutes. It is conveniently located on the front of the engine, and requires a 22mm deep socket to remove and reinstall it.
1. Cylinder head temperature sensor (required) – Always purchase a quality sensor from a reputable manufacturer. Cheap generic sensors have a high failure rate. We give you several high quality choices based on your brand preference and budget.
Removing and installing the BMW N20 cylinder head temperature sensor in your four cylinder engine is very simple. It is conveniently located on the front of the engine and easily accessible without having to clear any parts out of the way.
- Locate and identify the cylinder head temperature sensor. It is on the front of the engine as shown in the images below.
- Pinch in the metal locking clip on the temperature sensor’s electrical plug. Pull the plug off of the sensor.
- Using a 22mm deep socket wrench, remove the BMW N20 cylinder head temperature sensor from the cylinder head.
- A small amount of engine coolant may drip out of the open hole after the sensor is removed, so have a rag ready.
- Install the new sensor into the cylinder and finger tighten. Torque the new BMW N20 cylinder head temperature sensor to 11 Nm (8 ft-lb).
- It is always good practice to spray the electrical plug liberally with CRC Electronic Cleaner to remove any dirt, oil or old coolant.
- Replace the plug. Make sure it snaps securely into place.