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There are a few things you need before you start:-...
1)... A jumper – this can be as simple as a paper clip
2)... An LED – ideally one you can actual see
3)... The ability to count! If you can’t count then you shouldn’t be trying this!
You can buy a great book written by John Cookson which includes the LED and much more detailed instructions. It’s about £10 inclusive and probably the best little book you’ll ever buy for your MX5.
Here’s the link – Diagnostic Book
https://www.autolinkmx5.com/diagnostic- ... -322-p.asp
1)..... Check the Obvious Things on the Car, May want to check the following, It’s worth thinking about these before you start work….:....
Fuses
Fuel – is there any in the tank? Remember the fuel is under pressure in the fuel rail!
Ignition – is there a spark
HT Leads – MX5s tend to consume these every 30k miles so it might be worth checking them.
Immobiliser
Is the timing or cam belt broken?
How’s the engine compression?
2).... First you need to locate the DiagnosticPort.....
You’ll find the diagnostic port on the right hand side of the engine as you are looking into the bonnet. It’s a little box about 50mm x 30mm.
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Open the lid – there’re some helpful descriptions / labels inside the lid.....
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3).... Plug the “jumper” in to ports GND and TEN.....
****Remember this is VERY important – MAKE SURE YOU KNOW WHERE THESE ARE BEFORE YOU PUT THE JUMPER IN*****.....
We used a simple piece of wire to hand for this but recommend a paper clip as it is more stable when pushed into place...
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This over-rides the control functions of the ECU. (This is also how you set the base idle.) Some faults mean the car won’t start but the ECU will hold fault codes.
4).... Plug the LED in to ports FEN and +B....
Plug the LED negative terminal into the FEN port....Plug the LED positive terminal into the +B port.
***NOTE: Port +B is a direct connection to the battery!****
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5)..... Switch Ignition On, but do not turn her over....
The LED will illuminate for 3 seconds – this in confirming that the diagnostic system is operational.
6)..... Read the Fault Codes.....
Fault codes are reported as a series of flashes.....A long flash (1.2 seconds) = 10 digits in fault codes....A short flash ((0.4 seconds) = one digit in fault codes...Write these codes down and check the list for details...THERE IS A PAUSE BETWEEN FAULT CODES OF 4 SECONDS....
Examples of fault codes:.....
Three long flashes and four short flashes = 3x10 plus 4x1 = 34 (Idle Speed Control Value)
Eight short flashes = 8x1 = 8 (Airflow Meter)
7).... This is the List of Codes...
***Note: Some codes are specific to 1.8s****
*****Some of these codes are common with MK2s BUT haven’t checked them yet.*****
01 – Ignition Pulse – No signal – check the igniter, coils and wiring.
02 – Ne Signal – No Signal – Check Cam Angle Sensor
03 – G Signal (or SGT on 1.8) - Check Cam Angle Sensor
04 – SGC Signal (1.8) - Check Cam Angle Sensor
08 – Airflow Meter – Open or Short Circuit
09 – Water Thermistor – Open or Short Circuit
10 – Intake Air Thermistor in Airflow Meter - – Open or Short Circuit
12 – Throttle Position Sensor (TPS) – Open or Short Circuit
14 – Atmospheric Pressure Sensor - – Open or Short Circuit
15 – Oxygen Sensor (output low) – Sensor or Wiring Fault
16 EGR Function Sensor (1.8) – Open or Short Circuit
17 – Oxygen Sensor (output not changing) – Lean / Rich Running Fault
25 – PRC Solenoid Value (1.8) - – Open or Short Circuit
26 – Solenoid Value (Evaporative Canister Purge) – Open or Short Circuit
28 – EGR Solenoid Value (Vacuum 1.8) – Open or Short Circuit
29 – EGR Solenoid Vale (Vent 1.8) – Open or Short Circuit
34 – Idle Speed Control Value – Open or Short Circuit
8).... Solve the Problem and Re-Test.....
There is a whole load more information in John’s book – buy it – it’s really is an invaluable tool!
***Submitted by Skuzzel***
