Hi Greg,
I had this issue with a 2016 ND a few years ago after I started the engine without actually getting in! (Don't ask ðŸ¤) I pressed the clutch pedal down with my hand and started the engine to warm it up whilst I finished my cup of tea!! 🙄 From then on I had all kinds of issues!! Resetting using the method you described (holding in the start button) worked and cleared the faults. It appears that not sitting on the seat and activating the seatbelt alert throws the whole ECU into a wobbly!! If that's not relevant in your case, you might need to renew the batteries in both keys. Try that first anyway---they don't last for ever---failing that you'll need to recharge the main battery and get the car plugged into an OBD II code reader and see what that shows. By the way, main batteries fitted to Mk3 (NC) and Mk4 (ND) MX-5s are extremely marginal and not long-lived, so you might still need to fork out for a new one. I recommend a higher capacty Yuasa battery, which work well and last much longer 🙂
I had this issue with a 2016 ND a few years ago after I started the engine without actually getting in! (Don't ask ðŸ¤) I pressed the clutch pedal down with my hand and started the engine to warm it up whilst I finished my cup of tea!! 🙄 From then on I had all kinds of issues!! Resetting using the method you described (holding in the start button) worked and cleared the faults. It appears that not sitting on the seat and activating the seatbelt alert throws the whole ECU into a wobbly!! If that's not relevant in your case, you might need to renew the batteries in both keys. Try that first anyway---they don't last for ever---failing that you'll need to recharge the main battery and get the car plugged into an OBD II code reader and see what that shows. By the way, main batteries fitted to Mk3 (NC) and Mk4 (ND) MX-5s are extremely marginal and not long-lived, so you might still need to fork out for a new one. I recommend a higher capacty Yuasa battery, which work well and last much longer 🙂
