The Cam Angle Sensor (CAS) as a unit consists of three parts. These are easily viewable on the car when removing the black dust cover. 1) the central spinning notched Reflector Wheel, 2) the Hall Effect sensor on the bottom which provides the timing reference for the injection sequence; and, 3) the magnetic pickup for rpm data. See also Charlie’s writeup of repairing the Hall Effect sensor which has great pictures of these parts.

It is the Hall Effect sensor which causes the engine check light to come on and causes engine running problems. A Code 41 error is reported at the ALDL and turns on the engine check light when the ECM does not receive signal pulses for more than twenty engine revolutions or it does not receive signal pulses for more than 5 seconds

Lotus have now released a new Hall Effect Sensor, which is available as a seperate part, the usual price is £97+vat, however Lotus currently have these on sale (correct as of 08.07.05) for just £20 +vat, you will need to order one through you local main lotus dealer, part number: A100E0102S. When the item arrives, you’ll notice that Lotus have taken the opportunity to redesign it somewhat (see picture below). In the picture, you can see the old style sensor on the left and the ‘new’ redesigned sensor on the right.

Now, there is a down side to the new HAL sensor and those observant of you will have noticed the addition of a connector ‘fly’ lead. In order to fit the new sensor, you’ll need to remove the old wiring loom connector and replace it with the one above. The sensor kit contains all the instructions, the female connector and all the necessary crimp pins and weather proofing grommets.

The pictures below show the new sensor fitted to the CAS assembly.

Lets hope this redesigned HAL sensor offers a lasting solution to our error code 41 problems. After fitting the CAS, complete with new HES, you need to reset your timing.

Many thanks to Darren, Doug, and others for the pages and writeups that were combined to make this page. Hopefully I've covered all of the information required in the update of this page, TStevens.