Immobilizer

The ECU, transponder ring & the transponder chip in the keyfob are the 3 parts that form the immobiliser circuit. Without these 3 parts, the car simply won’t start, so when you buy an engine, make sure to get these 3 parts! When I purchased mine, I didn’t have the transponder ring so I had to reprogram the ECU so that it didn’t expect to talk to the immobilizer. This worked fine but it left me with a car with less security so I purchased another ECU, immobilizer and transponder chip from ebay for £50.

Fitting the transponder ring in the steering column shroud is quite straight forward but you’ll need to cut the shroud a little. Luckily it fits around the MGB key barrel reasonably well. Once you’ve physically fitted it, you need to wire it in. My transponder came without the wiring loom so I was missing the plug. The pin spacing is a standard 2.54mm. A quick search of eBay turned up a JST-XH 2.54mm 9pin connector. This fitted into the socket quite tightly.

The wiring is as follows:-

Once this is fitted, you’ll need to insert the ECU transponder chip into the key fob. The easiest way to do this is to get a Landrover Discovery key blank. This has the same key blade as the MGB & has a space for the transponder chip to be inserted.