I have a problem with my mk 1.it always starts first time ,if the security light goes out the car runs fine,if the light stays on the car runs for 3or4 seconds then cuts out.tried a complete ecu immoblisor system with the same result.the car has ran fine on both systems,and have failed on both systems.please can you help.
Have you tried different ignition keys and have you tried a different ignition switch, essentially the black plastic pick up around the key hole in the ignition switch. Have you carried out a code read?
Hi Robbie.tried different keys in original switch,also tried new switch, pickup, immobilisor,and matching ecu off doner car.had the same problem on both systems.car ran fine all last week,untill sunday morning when it started ok but security light did not go out,so new car would cut out.still starts but wont run.have carried out code readings .6=16 EGR function sensor.10 airflow meter.12 throttle pos. sens. and 11 witch is not on the code reading.have got mx5 immobilizer system training manual, but cant find anything to help.thanks for trying to help.
That code is a 4 digit code, so is in fact one code of P6021. I’ll have to look in the WSM to see what the code is for.
I think the code is in fact P1602 (P6021 doesn’t exist). You need to be sure of which order the codes are output to be sure. You ignore the tens digit and just use the units digit (P1602 is output as 11,16,10,12 in that order). If you can confirm that it is P1602 then that points to a communication problem between the engine ECU and the immobiliser unit. It could be a faulty engine ECU, a faulty immobiliser unit or a wiring fault between the 2. If you’ve eliminated the immobiliser unit then that just leaves the ECU or the wiring. I’ve not got a wiring diagram to hand to check which wire you need to look at. Can you confirm the fault code first?
hi Robbie.my fault codes read long flash 1short/longflash 6short/long flash/long flash 2short/then it repeats itself.on the info I have it says long flash=10+short flashes.eg.long+6=16=EGRsensor. it was written by fletcher blades.autolink mx5. MK1 diagnostic fault codes.my car is a 96 merlot.only done 46000.thanks john.
A 96 car will be on four digit fault codes so I think you’re getting P1602 by your description. Seems you’re looking at an ECU or wiring issue as you’ve eliminated the immobiliser unit.
The information you have is not applicable to your car. Early cars (pre 300001 VIN serial number from memory) had 2 digit fault codes.
I’ll find out which is the communication wire between the ECU & immobiliser unit so you can check it. May not be until after Brooklands now though. What is your VIN?
hi Robbie. my vin is JMZNA18P200307429.
The Blue Wire is the communication link between the ECU and the immobiliser unit.
I have an ECU, immobiliser unit and keys from a Merlot if you are interested in buying them…
hi Robbie,is it a thin blue wire that goes into a thicker grey wire.i have a complete immobiliser, ecu unit with the same ident.numbers as my car.see post 3.thanks .john.
Probably, it has a shield wire which is the grey part.
hi Robbie.the blue wire seems ok. used another wire as link but still same result.starts fine,runs for a few seconds then cuts out.what to do now ? thanks john.
What fault codes are you getting now? You’ve exhausted pretty much all options now. Are you sure the donor parts that you have are good?
hi Robbie.think we have cracked it.a friend who has been trying to sort the problem with your info cut the blue signal wire close to the ecu and the immob.connected a new wire with croc. clips and all seems fine at the moment.will start the car off and on for the next few days and see how it goes.will let you now how it goes .thanks,john.