Hi All,
Im scratching my head at the minute and may have stumbled onto the issue but thought as I would ask those with more knowledge than myself.
I used to own an MX5 Mk1 (1994) which was my pride and joy for many years until I got promoted and was eligible for a company car and on the scheme the MX5 was a tad outside the 6 years I was allowed the car to be. Anyway the eventual think happened where the other half made me sell my Mazda to save money but then 2 weeks after she sold had someone else crash into her car writting it off. She then decided she actually liked the MX5’s and we went and got her an MX5 Mk2 after a while of looking as she didnt like the pop up headlights!
Anyway cutting a long story alot shorter (you can see my frustration at least) the Mk2 has since developed a cold start issue. The car starts but struggles to hold idle for around 5-10 minutes after starting but only on cold days so currently starts but is still not as happy as she should be. In an effort to diagnose the issue I got out my LED which I had used on the previous car as hers in the Mk2 and is a 1999 model and does not have the OBD11 connector so thourght this would give me where the ECU thinks the issue is. I duly noted the codes it gave out which appeared to be 2 errors. The first was a long flash suggesting what I thought was an error 10 and the second was a long flash followed by 5 short flashes suggesting an error code of 15, it then repeats the two error codes so hence why I think it is an error of 10 & 15 suggesting the Intake temp sensor and the Lambda Sensor. Ive replaced both sensors and reset the error only to find when I drive it again the issue is still there and the error code comes back up on the LED when I plug it in. I have also since managed to get to the ECU and tested the cables running to the ECU which are all showing as no issues when I do a continuity test so was thinking the issue could be down to the ECU itself. On that bases I was going to ask if there was anyway of checking the ECU as I did notice it was quite warm when the ignition was on but have also found some information around on the later Mk1’s and Mk2 cars the codes changed from a 2 digit code to a 4 digit code but am unable to find any further information on if this is the case.
This is where Im hoping you may be able to help me with. As mentioned the car is a Mk2 1999 MX5 UK model of the car. Do any of you know if this should have the newer 4 digit codes and if there is any difference in how to test for this as so far all my searches have drawn up a blank. This could explain alot as if the error codes are different then the sensors I have changed may not be what the codes are flashing for. I have found a manual on this forum but as my membership has expired for the MX5OC (I assume this is the reason) I am unable to download the guide (This is the guide I found). I did also find this book on a site which says it could contain the code but I wasnt keen on buying it if it doesnt contain the codes. I can find all the codes for the original Mk1 cars online and having bought the LED already from MX5Parts was hoping I could just find the codes online to compare and an update on how to read the codes but have been unsuccessful so If any of you can confirm the model is a different code to my original Mk1 and if you know if the book on this link will help me Ill happily buy it to find out what the real issue the car is telling me it has after all it is only around a tenner plus postage. (If only the car spoke English!!!)
Hoping someone can help and if any one is able to email me the details of the codes and how to read them I will be even happier 
Thanks for all of you for taking the time to read and assist if possible. If you ask any additional info I will post as requested. I may even try videoing the error light and uploading it to the post if that is any help. I will be using the standard cable between Fen/Ten & LED connecting Gnd/B+.
Andy B, (Now) Mazda MX5 Mk2 1999 near High Wycombe.