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M54 Engine Coolant Temperature Sensor Replacing & Testing
 
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Pelican Technical Article:

M54 Engine Coolant Temperature Sensor Replacing & Testing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$45

Talent:

****

Tools:

22mm wrench, flathead screwdriver, digital multi-meter, jumper wires

Applicable Models:

BMW X3 Sport Utility (2004-06)

Parts Required:

Engine coolant sensor

Hot Tip:

Work with a cool engine.

Performance Gain:

Remedy a check engine light or incorrect engine temp gauge

Complementary Modification:

Replace coolant at same time

The engine coolant temperature sensor is responsible for sending the temperature of the engine to the DME and the instrument cluster. It is a two wire negative temperature coefficient (NTC) sensor. If you have a coolant sensor fault code stored in your DME and your engine isn't running right, I suggest replacing the sensor before digging too deep. You may also have an inaccurate temperature gauge in your instrument cluster, this can also be from a faulty sensor.

The sensor is mounted to the rear of the cylinder head in a coolant passage. The intake manifold has to be removed to access it.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please include your vehicle information.

Relieve cooling system pressure by opening reservoir cap. If needed, drain cooling system. Most times I won't drain it. I will remove the sensor and catch what leaks in a pan below the engine.

The sensor is mounted to the rear of the cylinder head (red arrow) in a coolant passage.
Figure 1

The sensor is mounted to the rear of the cylinder head (red arrow) in a coolant passage. The intake manifold has to be removed to access it. See our tech article on intake manifold replacing.

Working at rear of the cylinder head, locate the coolant temp sensor (red arrow).
Figure 2

Working at rear of the cylinder head, locate the coolant temp sensor (red arrow).

Then, disconnect the sensor electrical connector by pressing the wire release and pulling it straight off the sensor (red arrow).
Figure 3

Then, disconnect the sensor electrical connector by pressing the wire release and pulling it straight off the sensor (red arrow).

Now you can loosen the sensor (red arrow).
Figure 4

Now you can loosen the sensor (red arrow). Use a 22mm open end wrench and loosen the sensor about a half turn. This should be enough to remove it by hand the remainder of the way. Unscrew the sensor and remove it from the engine.

Place a rag under the sensor and unscrew to remove.
Figure 5

Place a rag under the sensor and unscrew to remove. Be sure to replace the metal sealing washer (red arrow) when replacing the sensor. Install new sensor finger tight. Then tighten it using an open end wrench. Be careful, it is easy to over-tighten the sensor. Reassemble engine. Top up and bleed cooling system.

I am going to show you a few quick ways to test the coolant temp sensor.
Figure 6

I am going to show you a few quick ways to test the coolant temp sensor. This photo shows the coolant sensor electrical pins. To test the sensor, connect you volt meter across two of the terminals and take a resistance reading. At 60f you should have about 4.5k Ohms between terminals 1 & 2 (red arrows). Now insert the sensor into warm water, as the temp increases, resistance should decrease. Keep in mind, these are rough specs. I rarely test coolant sensors this way, mostly because they are either shorted or have an intermittent connection. I prefer to test the circuits back to the monitoring devices, if the circuits are good, I will replace the sensor. Jump Pin 1 and Pin 2 together on the connector (blue arrow) while monitoring the instrument cluster. When the circuit is open, the temp gauge will read cold. When you jump the terminals together the temp gauge will read hot.

You can also test the voltage (red arrow) from the DME to the sensor.
Figure 7

You can also test the voltage (red arrow) from the DME to the sensor. Terminal 1 should have about 5 volts. Terminal 2 should have about 0.1 volts. Confirm terminal numbers for your vehicle using a current wiring diagram.

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Comments and Suggestions:
Gk1990 Comments: 2005 bmw e83 x3 automatic with the m54b32 engine what is the normal operating temperature of this motor?I read on another site that the coolant gauge rather than reading coolant temp reads oil temp is that correct? And it's my first time having a bmw this new so is it normal for these newer ones for the coolant temp gauge on the cluster to rise fast to the middle or should it rise slow
March 21, 2017
  Followup from the Pelican Staff: The temp gauge in the instrument panel reads engine coolant temp. However, it does not report accurate readings. It is programmed to prevent fast swings and reports more general temps, for example cold, operating temp and overheating. The engine will run 200-220°f. - Nick at Pelican Parts  

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Page last updated: Mon 3/27/2017 03:15:38 AM