How to Retrieve and Translate Engine Fault Codes using the Diagnostic Connector on Mk1 (NA) & Mk2 (NB) MX5 Miata Eunos 1989 to 2002 Models.
Retrieving Engine Fault Codes
The video below will show you how to read Engine fault codes yourself using the diagnostic connector and a LED. LEDs should be paired with an appropriate resistor for the voltage (12v) and color of the LED. Sounds complicated, however most 12v automotive LEDs you can buy from places like eBay already come paired with the correct resistor and so I use one of these. A summary of the steps taken in this video are shown underneath for those confident enough to get started right away.How To Retrieve Engine Fault Codes
Summary of Steps:
1. With the ignition off, connect the TEN terminal to one of the several GND terminals using a jumper wire or paperclip. Now, connect the indicator LED between terminals B+ and FEN, with whichever side of the diode had the long (+) lead towards B+ (If you get it the wrong way around, no damage will be done, you’ll just get no light out of it).
2. Turn on the ignition switch, but don’t start the engine. The LED indicator will light up for a few seconds (assuming you got it the right way round) before it starts flashing out the error codes (if present).
3. Count the number of long and short flashes to indicate the malfunction code. If the code is a two-digit number, the tens digit will be displayed first with a long flash, then after a 1.6-second pause, the ones digit will be displayed with shorter flashes. If there are multiple codes, they will each be separated by a four-second pause. Once all codes are output, they will be repeated after around 4 seconds.
4. Turn off the ignition switch, remove the LED and jumper wire from the diagnostic connector. Refer to the listing below to discover the meaning of each DTC (Diagnostic Trouble Code).
The Diagnostic Connector
Cars built prior to 2002 have a useful Diagnostic Connector located under the hood, above the wing, as shown in the picture below. You can use this diagnostic connector to trace a number of faults in a number of different systems, including; Engine Fault Codes, ABS (Anti-Lock Brakes), and any faults related to the cars Supplementary Restraint System (Airbags etc). You can do this yourself without the need for any special scanners, or a costly visit to your local Mazda dealer, all you need is a LED and resistor, but you only need that for engine codes, other faults are indicated via the corresponding dashboard indicators.
Cars built after 2002 (and sometimes earlier in other parts of the world) are fitted with an OBDII Connector located at the top of the cabin fuse box, underneath the steering wheel. An OBDII Scan Tool is required to read and clear error codes on these cars.
OBD Connector Pin Out Diagram
 |
| Bridge GND and TEN Terminals, Connect LED+ to B+ and LED- to FEN |
Translating Engine Fault Codes
Use the information below to look up the meaning of any outputted fault codes from your engine. Codes will be output once the LED indicator light extinguishes for the first time, and then shown as a series of long and short flashes. Count the number of long flashes, these are the tens, then count the short flashes, the units. Four long flashes followed by three short flashes would indicate fault code 43. Multiple codes are output one at a time, separated by a pause.MX5 Engine DTC Fault Codes;
1 -- Ignition pulse
2 -- Ne signal
3 -- G signal
4 -- SGT signal (1.8L)
8 -- Airflow meter
9 -- Water thermistor
10 - Intake air thermistor in airflow meter
12 - Throttle position sensor
14 -Atmospheric pressure sensor
15 - Oxygen sensor (output too low)
16 - EGR function sensor (1.8L)
17 - Oxygen sensor (output not changing)
25 - PRC solenoid valve (1.8L)
26 - Solenoid valve (Evaporative canister purge)
27 - EGR solenoid valve (vacuum)(1.8L)
28 - EGR solenoid valve (vent)(1.8L)
34 - Idle air control (1.8L)
36 - Idle speed control valve
Clearing Engine Fault Codes
Most (but not all) fault codes will remain in memory until they are cleared. It is a good idea to clear all codes before starting to diagnose faults, to ensure all codes are current.To clear all your engine fault codes, remove the jumper cable from the diagnostic connector, disconnect the battery Negative (-) cable, then press the brake, and sound the horn to remove any excess power from the system. Reconnect the battery again after about 20 seconds. You may then need to start and drive the car a short distance to refresh any faults that may be discovered by the On-Board Diagnostic system.
Did you find this article useful? Have a tip for reading Engine fault codes? Please leave a comment below.