The crankshaft position sensor is used to synchronize the engine timing for fuel and ignition control. It is located near the starter motor, mounted in the engine block. The sensors read a toothed-reluctor wheel mounted to the end of the crankshaft. It then sends a signal to the DME used to identify cylinder location. If this signal is missing, for example from a faulty crankshaft sensor, then your engine will not start. You can consider the signal from the crankshaft sensor the RPM signal for the DME.
In this article, I’ll go over the steps involved with replacing the BMW E46 crankshaft position sensor. You can access the sensor from below vehicle, working on the left side. The photos in this article show the throttle housing removed from vehicle for clarity, you do not have to remove it to replace your crankshaft sensor.
First raise and support the front of your vehicle safely. Remove the lower engine plastic splash shield.
The BMW crankshaft position sensor is located below the starter motor (yellow arrow) at left side of engine - disconnect the crankshaft sensor electrical connector by squeezing the release tab and pulling it away from the sensor (green arrow).
Once the Allen bolt is removed, pull the crankshaft sensor out of the engine block. Be sure the sealing o-ring comes out with the sensor. If it stays in the block, retrieve it with a small pick (yellow arrow).
I like to keep things clean so use a rag to
wipe the area around the crankshaft sensor then install your new
BMW E46 sensor and sealing o-ring. Torque the sensor to engine
block to factory specs. Reconnect the electrical connector and
install the engine splash shield. Start the vehicle and allow it
to idle for about 1 minute. Check that the crankshaft sensor
area is free of oil leaks. If your check engine was on, now
would be the time to clear any DME fault codes using a BMW compatible scan tool or a code reader. Follow the instructions accompanying your code reader or scanner.
Comments: Thats what i thought. Here are some more clues to this no start mystery: When i push the start button the engine will continuously crank until i either let the clutch pedal out or push the start button to stop the cranking . Also i cant get any code reader to link to the vehicle. Not even a new matco scanner or even a snap on scanner. i think it was a solus??? anyways, i have bench tested every relay that i could find on the vehicle along with all of the fuses. I cant find a wiring schematic anywhere for this car. Its a 4 door 325i. The manufacture date is 06/2005.
February 7, 2015
Followup from the Pelican Staff: The cranking scenario is normal, it will crank for a defined amount of time, until it start - or not.
if you can't communicate with the DME, I would this the issue may it. Check if the DME is receiving power and ground, good ignition power. Then check the data lines. If all is OK and the DME is not functioning, it may be faulty.- Nick at Pelican Parts
Comments: F1 fuse is good. Is the dme relay supposed to power up when the ignition is turned on or does the ecu have to receive crankshaft position signal while cranking before it powers up the relay? Would a bad crankshaft position sensor prevent the dme relay from turning on?? Also what is the purpose of the resistor that is located on the cap for the obd2 port?
February 5, 2015
Followup from the Pelican Staff: No, the crank sensor would not. The DME relay should be on when the key is in the run position. - Nick at Pelican Parts
Comments: Hello pelican i have a 2005 325i that cranks but wont fire. Now here is what i have found: no power to ignition coils while cranking, all fuses are good , plenty of fuel pressure, cant get code scanner to link to vehicle. Ebox fuses are all good. The relay that powers the coils is good.... Im stumped!
February 3, 2015
Followup from the Pelican Staff: No power to the coils, power comes from the DME relay (located engine compartment e-box) Fuse F1 in the front e-box as well. Start there.- Nick at Pelican Parts
Comments: My son has a BMW 2001 330ci that started running poorly and dash lights came on. he checked the codes they said bad mass flow sensor and crankshaft sensor. He pulled the connections loose and cleaned them and plugged back in and cleared codes. It seemed to run better for a short time then bad again. He checked codes and it showed an intermittent bad crank pos. sensor again. He replaced the sensor and cleared codes he started it up and ran it for a bit and lights on dash where all on and car seem rough. He checked codes again and it showed fulltime bad crank pos. sensor again and it won't let him clear that code no other codes showing. It still driving poorly low power limp home mode and dash lights on. I read a few places DME and ECU need resetting but that's a shop or dealer thing. Any ideas about problem ?
January 26, 2015
Followup from the Pelican Staff: I would check the signal from the crank sensor to the DME. You may have a damaged wiring harness. - Nick at Pelican Parts
Comments: BMW 3251 1995 when i start it , and it warms up , a min .the timing seems to be off a little. anyThing electric radio, windows exccelerating the pedal,the idle seems to waver .....like its t timing belt, or dcould it be a sensor
January 10, 2015
Followup from the Pelican Staff: I would start by checking the charging system. Your issue may be low voltage. - Nick at Pelican Parts
Comments: Would this procedure work for a 2004 330ci?
January 1, 2015
Followup from the Pelican Staff: Yes. - Nick at Pelican Parts
Comments: My BMW e46 M54 engine 2000 model has a bad take off as well as shutting down in traffic with dead slow speed or when stationery in traffic, however your explanation I conclude it could be the Crankshaft Sensor. Kindly advise before I buy a new sensor?
October 7, 2014
Followup from the Pelican Staff: I have seem camshaft and crankshaft sensors cause this issue. I would start by checking the DME for fault codes. If the system is not working properly, a fault code will be set. This will be your best bet when diagnosing.
- Nick at Pelican Parts
Comments: Hi. I have a 2003 325i. Two days ago my passenger window was stuck when i lowered it all the way, took it to my mechanic. Today he told me the window motor is okay but he thinks the crankshaft sensor is bad since the car did not start. he powered the window from outside which worked.
Also, i have the following codes from the engine light:P2240 heated oxygen sensor bank 2, P2237 heated oxygen sensor bank 1, P0174 system too lean bank2, fuel pressure or volume.
can you help explain all this please?
September 4, 2014
Followup from the Pelican Staff: The codes for the o2 sensors need to be dealt with first, then you can address the fuel trim fault if it is still present. CHeck oxygen sensor operation and replace as needed. Then clear the fault codes and see if the fuel trim fault returns. I do not see the correlation to a crank sensor. - Nick at Pelican Parts
Comments: The click to order parts takes you to a horn, not the sensor.
July 22, 2014
Followup from the Pelican Staff: Thanks for catching the link error. I will have it fixed. - Nick at Pelican Parts
Comments: alright cool cool so should i remove the starter?
November 18, 2013
Followup from the Pelican Staff: If you need the space, yes. - Nick at Pelican Parts
Comments: where are you located maybe i can bring the car to you, and what kind of vise grip, the bolt looks chipped out, also were can i get another bolt n would i brake around the senor
November 18, 2013
Followup from the Pelican Staff:
Just a small vise grip, pretty standard. They come in all sizes. You can get a bolt from Pelican Parts, Give our parts specialists a call at 1-888-280-7799. They can help you find the right bolt.
If you remove some of the sensor mounting material you should be able to get a better grip.
If there is any hope for the Allen fastener, you can also try to hammer a larger sized Allen bit into the fastener. I always go one size bigger in a fractional sized bit. if you use this method, do not hammer hard on the crankcase. The bit should go in with light tapping. You don;t want to damage the engine.- Nick at Pelican Parts
Comments: a vise grip is to big to fit in there remember this is a bmw 323i its in a very tight spot and i do not have a extra bolt to replace it
November 18, 2013
Followup from the Pelican Staff: If the bolt is rusty, you are going to have to replace it. I have small vise grips that would fit in the space, so that is an option. If you need to make room, you can remove the starter. - Nick at Pelican Parts
Comments: i am trying to replace my sensor on my e 46 but the thing is the bolt is rusted and stripped also chipped out what cant i do ???
November 18, 2013
Followup from the Pelican Staff: You can use vise grips to grab and remove the bolt. Or break the sensor away from the bolt, the plastic portion of it. Then use vise grips to grab the bolt. - Nick at Pelican Parts
Check out some other sample projects
from the book: