by the GoMoG Webmaster

N.B. To properly choose your new chip, assure yourself it will function with the EFI diagnostic units available for your engine.

Firstly, any automobile ECU,  even more so than a normal computer, can be easily damaged by static electricity. To avoid these problems, computers are normally worked on in specialized environments which reduce the possible of a destructive charge. If you are not working in such an environment, you can reduce the inherent risks by grounding the surface you are working on. For example, you can use a metal desk or a sink top draining area or use foil on the surface you are using. Wear natural fabrics rather than synthetics as well.

1. Have your old chip and engine checked out a dealer with a diagnostic unit to make absolutely sure there are no pre-existing engine faults.

2. After you have your work area set up, disconnect the battery. This makes absolutely sure that the ECU is completely unpowered.

3. Disconnect the securing screws for the wiring plug. and gently pry it off the ECU.

4. Unscrew the larger screws (normally at the corners),  that hold the ECU onto the car and pull the ECU from the car;

5. After you place the ECU on your grounded work area, unscrew the screws holding the lid to the ECU. (5 screws on a Rover).

6. The circuit board is now visible and may be released by unscrewing the screws that hold it in place (6-8 of them)

N.B. Prepare for a shock! Some Rover and other units have a  warning system to prevent tampering which will actually spurt a clear liquid out at you like a disturbed infant. It is no danger though and it will disappear quickly leaving a residue of human fright only. (smile)

7. In most ECUs and most Rovers as well, the chips are fitted in sockets.

N.B. On older Rovers, if you have a label on your Eprom (chip), it is a socket type but if the Eprom has no label you will probably have to buy a socket attachments and install it for your new chip.  

N.B. Newer Rovers also have two "chips". One is blue plastic (the larger one) and the other is green each with a Lucas stamped on it..which will overwhelm you with confidence.

The cover must be removed by gripping it in the middle with long nosed pliers. Wiggle the cover gently from side to side to release it from the circuit board below. When loose, the chip itself may be removed by carefully levering it up and out using a small flathead screwdriver between the Eprom and its socket.

Take extreme care not to bend the pins of the old EPROM as it releases. Be equally tender with the chip socket and the circuit board at all times.

8. Note to the orientation of the chip or chips as the new chip must be fitted the same way exactly as the one it replaces. If this is done wrong, you will probably destroy the new chip at ignition or soon after.

N.B. With the newer Rovers, the green decoder board and the EPROM are marked with a red paint spot by pin number one. The Eprom socket on the circuit board also has a little notch at one end which identifies the pin one position. PLEASE NOTE however that Lucas has been known to fit the chip sockets incorrectly so pay close attention to the way the original chip was fitted and you should be all right.

9. Carefully orient and slide the new chip into the socket making sure all the chips' pins enter the socket without a problem. It is very very easy to have a pin fold underneath while inserting. Use a magnifying glass if necessary to get this right. After alignment and first entry, a good firm press will be required to seat the devices in the circuit.

N.B. With newer Rovers, the fitting order of the components is the green decoder board fitting into the socket on the ECU circuit board, and the EPROM fits into the decoder board.

10.  Now reassemble the ECU casing and label the outside of the ECU with the new chip type you have installed.

N.B. ALWAYS KEEP YOUR OLD EPROM CHIPS!!! Remember the problems and dangers with static electricity and store the chips appropriately.

11. Refit the ECU into the car by reversing the removal procedure. When the ignition is turned on for the first time without starting the engine, the fuel pump will be heard for a few seconds and then stop.

N.B. For newer Rover please note that the Lucas-Sagem GEMS system is adaptive, and it "learns" how to manage the engine over the first couple of hundred miles. It continues after that to deal with your driving style over the next 2-3K miles.

You should see an immediate but small improvement in performance but it will take the 200 miles to show the real improvement.


A. The fuel pump doesn't run for a few seconds, or runs continuously when the ignition is turned on. This means that at least one chip is probably plugged in the wrong way round or ( more rarely) one of the chip prongs is bent. Alternatively, the ( UGH!!) ECU has been damaged during the process, or the EPROM or the whole ECU is not plugged in.  

B. The EPROM was installed the wrong way, you tried to start it and it fried. Both the CHIP (and with Rovers the decoder) have unique signatures all their own which will both be destroyed in this situation and are then useless. Normally you can make a deal with the chip supplier if you own up and return them.

C. The engine is hard to start and/or or runs badly. This normally indicates that the ECU is registering fault codes...which   have been present before the new chip was installed. This should have been noticed and dealt with before (see the beginning of this article) but occasionally a new chip can aggravate an existing fault. Find a dealer with a diagnostic unit and that should help.

D. No improvement in performance could mean you have installed a poorly designed or wrong chip.

N.B. For Rovers, look for "TESTBOOK" or  Allpart's "ROVERCOM".

It is understood that the information contained herein is offered without any
undertaking whatsoever and no warranty is suggested or may be implied.