Hi guys-new to this, hope you can help. Have a Mk2 1.6 2001. Engine wont start unless airflow meter disconnected-then it will run but not good. Tried new airflow meter sensor but still not right. Looks like ECU may have been damaged with water ingress. Been told ECU can’t be repaired?? Been told Mazda won’t supply wiring diagram?? Would be extremeley grateful for any advice, tips or contacts that would avoid buying new ECU. Thanks very much-cheers, Sam.
New ecu is a fortune and immobiliser and keys.coding need to be replace dapprox 1200 to 1500stg.!!!yes crazy .but we have used ecu with matching immobiliser /keys etc .My email is robert.maguire@eircom.net .Give me a mail if this helps
Hi there,
I’m a mechanic and worked at a garage that specialized in diagnostics for 3 years and have seen a few ECUs with water ingress. I’d suggest taking out the ecu and drying it out with either a hair dryer on on the radiator ideally, just don’t get it too hot. If it is too hot to pick up then that is too hot! This may solve your problems as it will remove any residual moisture from the unit. Ideally you would open up the ECU and dry it that way but I know that a lot of people may not be comfortable doing this! Main thing is to make sure its dry and see what happens. Also make sure the connector block that goes into the ECU is dry as well. A good squirt of electrical contact cleaner will sort that for you. If after that it still doesn’t run properly then I suspect that the water damage did something permanently. Hope that helps! 
Forgot to mention ECU’s CAN BE REPAIRED, it’s just the dealers want to sell you a new one. If your’s is duff I would suggest finding a local garage that specialized in auto diagnostics and they will be able to get you a replacement at worst (still cheaper than main dealer) or possibly repaired. I’ve repaired a few ECU’s where the only problem has been a bad solder joint on a component.
Good used ecu,immobiliser unit and keys is only 250 stg from us so that would not justify getting your car to gagage,labour to repair ecu etc and refit .I can talk you through fitting ecu kit yourself as its as simple as pie.
As I recall, BBR had or have the contract with Mazda UK to repair ECUs from MX5s.
Hi
Many thanks for response & advice-much appreciated!