It’s always something, right? Usually electrical sensors are the most prominent, annoying, and expensive problems we have with these cars, and this only perpetuates this theory. Own an E39 M5 for long enough, and you’ll end up having to replace the cam sensors.
What is a Camshaft Position Sensor?
Let’s start with a camshaft. Put basically, the camshaft is responsible for opening and closing intake and exhaust valves in a combustion engine. A camshaft position sensor senses the position of the camshaft as it revolves, reporting back to the VANOS (variable intake and exhaust valve timing system) telling it where the camshaft sits. This all enhances performance, efficiency, and overall smoothness of the engine. Since the M5’s engine is a ‘V’8, there are two cylinder banks, and thus four camshafts. Each cylinder bank has one intake, and one exhaust camshaft. Each camshaft has a CPS (camshaft position sensor). This brings the total to four CPS, two intake, and two exhaust.
Symptoms
There are a few ways that you may be able to tell that you need new CPS sensors:
- Service Engine Soon light. There are several codes that could be faulted to bad CPS sensors. Using the Peake reader codes and definitions, here are a few:
07 “Intake camshaft position sensor, Cyl #1-4”
08 “Intake camshaft position sensor, Cyl #5-8”
0A “Exhaust camshaft position sensor, Cyl #1-4”
0B “Exhaust camshaft position sensor, Cyl #5-8”
B8 “Intake camshaft VANOS position control, Cyl #1-4”
B9 “Exhaust camshaft VANOS position control, Cyl#1-4”
71 “Intake camshaft VANOS position control, Cyl #5-8”
72 “Exhaust camshaft VANOS position control, Cyl #5-8”
- There are a number of actual performance differences that you may notice when driving your car. For me, the car usually started normally. After a few miles into the drive, the computer would know something was wrong, before I even would. To protect the engine, the computer engaged a fail-safe mode, which I could feel immediately. The torque below 4,000RPM virtually disappears, you need to let the car rev forever to go anywhere. It feels like 325 of the 400 horses just died in the stable. When you notice this, if you shut off and immediately re-start the car, it will throw the codes it sees to the computer. Also when starting when the car is in fail safe mode, you’ll notice a rough idle for a few seconds. It shouldn’t stall, but it struggles to hold a smooth, healthy idle at ~500 RPM. All of these symptoms can certainly be caused by bad CPS sensors.
VANOS, or CPS?
This is the problem. All of those codes that I listed above, can be controlled by the VANOS, or BMW’s variable valve timing system. The VANOS references the camshaft, the camshaft references the VANOS. This means that technically, either or both can be your problem. Bad news is, if your VANOS has a problem, it can be very expensive. I recommend you look at Dr. Vanos for some perspective. Each cylinder bank has four VANOS solenoids, one or more of these are usually the culprit. However, the good news is that camshaft positions sensors, especially intake sensors, are very well known for causing problems, and are ‘wearable’ parts just like oxygen sensors or spark plugs. It is much easier and cheaper to start with replacing the cam sensors, since they are the more likely cause of your trouble. I recommend replacing all of the sensors at once.
Replacement
When buying the replacement sensors, you will likely be confronted with several different brands. Dealers will always push the Genuine BMW. But the truth is, BMW does not, and has never manufactured cam sensors. They outsource the production of these sensors to other companies, such as Bosch, Hella, VDO, etc. In this case, Vemo is the manufacturer that BMW elected to use. You can buy this sensor for about 1/2 the cost as the one with the BMW logo. They are the exact same part. BMW doubles the price after etching their logo into the plastic.
Part Numbers:
(2) Intake Camshaft Position Sensor: 12147539173 (2) Exhaust Camshaft Position Sensor: 13627796054
Installation
On the S62 V8 found in the E39 M5, replacing the cam sensors is not a fun job. The sensors are located at the back of the valve covers, in between the engine and the firewall. One must first remove all of the cabin air filter box, housing, and tube into the firewall. You must also remove the upper plenum, velocity stacks, and lower plenum to gain access. There is then a bracket which must be removed from the back of the engine to gain access to the sensors, and all of this work is done with a mirror. You’d better have very small hands and the right tools if you plan to do this yourself. After my failed attempts, I took my sensors to my local BMW dealer, and let them install them. The job took the lead technician three hours. I was charged for only two hours of labor, totaling approximately $250. Be sure to watch the embedded video below if you wish to change them yourself, there are some helpful clips from Andrew changing his on his 2000 M5.
Note that even if your car has not thrown a CPS code, and is running normally, fresh CPS sensors can unlock some power, and fuel efficiency. The car doesn’t present a code until the camshaft is 60 degrees or more off from where it is expected. In other words, fresh sensors would be a good way to renew some performance from any BMW.
E39Source S62, CPS, VANOS Information:
Andrew’s Video About CPS Replacement: