BMW Z3 Resetting the Service Indicator
Article reproduced by kind permission of Mike Fishwick

The Service Indicator system operates the SI lights, which lose one of five green lights at a time, in response to the amount of fuel used – hard driving and/or cold running uses more fuel – changing to orange (Service due) and red (Service NOW!). The system also operates a two-year timer, which illuminates a clock symbol indicating that the coolant and brake fluid should be replaced.

The SI reset procedure requires that two sockets of the data link connector are joined together for a set period. This connector is alongside the engine, with a circular screw-on cap. Removal of the cap sets the system into ‘Service’ mode.

The clock cannot be reset without also resetting the SI lights, as it takes about 10 seconds of joining the contacts of the data link socket, whereas the SI lights only require about 4 seconds of joining the same contacts. (I forget the exact periods, but you get the idea)

Don’t take any notice of the SI lights anyway – you are better off changing the engine oil every 8 to 10,000 miles, and resetting the lights a bit after the second light goes out.

After this the performance deteriorates, and fuel consumption goes up – I am sure that the SI circuit sends a signal down the data bus to the engine ECU, telling it to begin retarding the ignition timing a few degrees every thousand miles. This means that after paying maybe £400 for a fancy oil change, the car goes a lot better, and the owner thinks that it was money well spent!

I once ran mine until the orange ‘Service NOW’ light was on, when the engine was really sluggish and struggled to make 30 mpg. I then reset the SI lights, and it was like having a new car!

A piece of wire is all that is required to reset the system, and although it is possible to buy specialist tools for this task, they only do the same thing – for £30 a time!

To reset the SI system, get a piece of wire which fits firmly into the sockets of the data link connector under the bonnet. Now turn the ignition on, insert the wire into the sockets which are in line with the ‘beak’ of the hole at the centre of the connector, on the outer edge – pins 1 and 7.

It maybe easier to use a piece of wire with a clip on one end, so that the earth (using the clip) can be disconnected more rapidly. In this case, the wire link would be connected to socket 7, and the clip earthed to any handy part of the engine, such as the lifting eye at the front.

After the appropriate time has passed, pull the wire out, and turn off the ignition. When you turn it on again, all 5 lights should be on, and also the clock symbol extinguished.