Setup and wiring notes for the 2001–2005 MX-5 (NB FL) running a DigiTune ME221 or ME442 ECU.
Clutch/neutral switch pin bridge (optional)
Gen2 ME221/ME442 ECUs can use the clutch and neutral switches to control idle entry and exit. The 2001–2005 MX-5 has these two switches on separate pins, but only the clutch switch is linked to a digital input. This means that, as standard, the 2001–2005 ME221/ME442 ECU cannot determine whether the car is in gear, and it may try to idle while still in gear. This often results in too much intake manifold vacuum and RPM dips when the clutch is pressed.
To prevent this, pins 4i and 4h can be bridged using solder (optionally with a small piece of wire) to link the clutch and neutral switch inputs. The combined input can then be used to control idle entry and exit. The pins circled in green below are the clutch and neutral inputs to be bridged. This modification is recommended but optional.
Wideband AFR gauge/controller
ME442 ECUs have an inbuilt wideband controller, so they do not require an additional gauge or controller. The ME221 does not have an inbuilt wideband controller, so an external wideband gauge is required. I recommend the AEM X-Series wideband AFR gauge:
AEM X-Series UEGO wideband sensor and gauge
Or an AEM wideband controller without a gauge, if preferred:
AEM X-Series wideband controller
Recommended wiring:
| AEM wire | Connection |
|---|---|
| Red | 12V switched live |
| Black | Chassis |
| White | Blue wire in the OEM narrowband lambda harness |
| Brown | Black wire with a red stripe in the OEM narrowband lambda harness |