Recently in our forums, user Tony Talton asked about the location of the camshaft position sensors on a 2001 Jaguar S-Type. The answer is simple, but the replacement is not.
What Do Camshaft Position Sensors Do?
Before jumping into the location and replacement, it's important to know what these sensors are actually for. Simply put, they send data to the engine control module (ECM, aka "computer") detailing the speed at which the camshaft is rotating and exactly what position it is in on its 360-degree spin. This information allows the ECM to tune the timing and detect if there are discrepancies in the engine. If the sensor goes bad, becomes disconnected, or otherwise stops regularly sending data to the computer, then an error code will trigger. Error codes 94 and 74 can be triggered by bad cam sensors. Symptoms will be rough running, occasional misses, bad idling, or even backfiring.
On modern, well-tuned engines, the camshaft position sensors are extremely important to the engine's operation. Because of their function, they are intimately tied in with the crankshaft position sensor as well, since they all run in timing with one another.
Where Is The Camshaft Position Sensor?
On the 2001 Jaguar S-Type, there are two possibilities. On a 6-cylinder (V6), the sensors are behind each cylinder head. On an 8-cylinder (V8), they are at the front of each cylinder head. In both cases, it's likely that the upper intake housing will have to be removed to get to the sensor plugs. There is one on each side of the engine (two in total).
The crank sensor is located next to the crank pulley on the front timing cover of the V6 or it can be found near the rear sump pan on the V8. These should not require that anything be removed to access them.
Replacement of the Cam Sensors
For the most part, replacement of the camshaft position sensors is easy. Any DIY mechanic with simple tools can do it, though a few caveats are in order.
First, the wiring will likely have to be replaced as well, which will require some creative "snaking" skills and the likely replacement of one or two plastic tabs which invariably get broken. The tabs (cable guides) are generic Jag wiring harness guides Pt# 12-14-1-743-197), available at most parts stores for a few cents each. You'll need at least two, but extras won't hurt.
Most of the work in replacement is in getting to the sensor and removal and replacement of the wiring. The sensor itself simply unscrews.