What is a Camshaft Position Sensor?
Let’s start with a camshaft. Put very 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 two camshafts. Each cylinder bank has one intake, and one exhaust CPS (camshaft position sensor) sensors. This brings the total to four CPS, two intake, and two exhaust, one of each per cylinder bank.
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 this car rev forever now to go anywhere, which is very un-like the infamous M5. It honestly 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 500RPM. 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 will 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. Mine lasted me 174,000 miles- no complaints.
Okay, so you’ve decided that you’re going to replace your CPS sensors. If your car only threw a code for, say, one intake sensor, I highly recommend replacing both. Like struts or tires, it’s best to do the intakes together, and the exhaust sensors together. However, ultimately, replace all four at the same time.
I purchased my two intake sensors from Bimmerzone.com. There are two parts to choose from: OEM and OE supplier. OEM sensors will have the BMW logo on them, and will be what the dealer would order for you. The OE supplier sensors are made by the same company that provided BMW with the sensors, but don’t have the BMW logo on them. For essentially the same part, but without the logo, they are about $30/piece cheaper. You can see Bimmerzone’s parts list here.
Intake Camshaft Position Sensor: VNE 9451910
Exhaust Camshaft Position Sensor: 13627796054
Each sensor by AB Electronic (OE supplier) is $99.95. Add $30 to get the BMW roundel.
On the S62 V8 found in the E39 M5, CPS install is not exactly what we’d consider easy. 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. There is 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 head 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.
To wrap things up, there is a very good likelihood that your intake camshaft position sensors are your problem. However, a professional diagnosis from a dealer is obviously the best way to go, though still not sure-fire. If you can replace the sensors yourself, then you’re set at just the price of the sensors. 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. Good luck!