Firmware Versions Covered
- MS2/Extra 3.3.1 or later
- MS3 1.2.4 or later
MS2/Extra — 4G63 Mode
MS2 has a dedicated 4G63 decoder. Follow a single set of instructions end‑to‑end—don’t mix guides.
Pinout used in this write‑up
| Signal | V3.0 | V3.57 |
|---|---|---|
| CKP | DB37 pin 24 | DB37 pin 24 |
| CMP | DB37 pin 5 (via SPR3) | DB15 pin 7 (via PAD7) |
| Spark A | DB37 pin 36 | DB37 pin 36 |
| Spark B | DB37 pin 6 | DB15 pin 10 |
MS2 V3.0 input mods
- CKP on VR circuit: TachSelect→VRIN, TSEL→VROUTINV.
- CMP: 1 kΩ from JS10 → SPR3, plus 470 Ω pull‑up from SPR3 → 5 V above proto. Add 0.1 μF cap‑mod JS10 → SG.
- CKP 5 V pull‑up: 470 Ω from VRIN → 5 V (proto).
- For PWM idle on V3.0, add a TIP120 at Q4 (MK‑PWMIAC).
MS2 V3.57 input mods
- Set JP1=1–2, J1=5–6 (VR input).
- CMP: 1 kΩ from JS10 → PAD7; 470 Ω pull‑up from PAD7 → 5 V above LED area. Add 0.1 μF cap‑mod JS10 → ground.
- CKP 5 V pull‑up: 1 kΩ at R57.
Ignition outputs (choose one)
Option 1 — Stock Mitsubishi ignitors (recommended)
- V3.0: two 270–330 Ω resistors from 5 V to LED negatives; route to DB37 IGN (pin 36) and SPR4 → pin 5.
- V3.57: pull‑ups exist; for lower value use 330 Ω from 5 V to PAD1 and PAD3. Wire PAD1 → Q16 center (Spark A), PAD3 → PAD15 (Spark B). Outputs appear on DB37 pin 36 and DB15 pin 10.
- TunerStudio: Spark Output = Going Low with these mods.
Option 2 — Internal BIP373 coil drivers
- Follow the BIP373 direct‑drive guide (one kit for V3.0, two for V3.57).
- TunerStudio: Spark Output = Going High and enable Dwell Control.
TunerStudio (MS2)
- Spark mode: 4G63
- Trigger Angle/Offset: 0 (verify with timing light)
- Ignition Input Capture: Falling edge
- Spark Output: Going Low (stock ignitors) or Going High (BIP373)
- Number of coils: Wasted Spark
- Spark A output: D14
- Cam input: JS10
MS3 + MS3X (including MS3‑Pro)
- Mainboard set for VR input: V3.0—TachSelect→VRIN, TSEL→VROUT; V3.57—JP1=1–2, J1=3–4.
- CMP pull‑up: fit JP7 on MS3X.
- CKP pull‑up: 1 kΩ external (pin 26 → 24) or internal (V3.0: 1 kΩ 5 V → TachSelect; V3.57: 1 kΩ at R57).
External wiring (MS3X)
- CKP → mainboard pin 24
- CMP → MS3X pin 32
- Spark A → MS3X pin 14
- Spark B → MS3X pin 33
TunerStudio (MS3/MS3X)
- Spark mode: 4G63
- Trigger Angle/Offset: 0
- Ignition Input Capture: Rising edge
- Spark Output: Going High
- Number of coils: Wasted Spark
- Spark hardware in use: MS3X Spark
- Cam input: MS3X Cam In
MS3‑Pro specifics: see manual section 5.3.14.
Other Systems
- Idle air: stepper IAC on MS2/MS3.
- Fuel pump: MS pin 37 → fuel‑pump relay.
- Boost control: use our boost control mod kit to drive the OE solenoid.
- Fans: relay control or MS3X outputs.
- Voltage regulator: 1G not ECU‑regulated; 2G uses ECU—swap to external regulator if deleting the OE ECU.
- A/C: relay control; MS2/Extra 3.3.1+ adds idle‑up input; MS3 has A/C strategies.
What to Order
MS3 + MS3X (most complete)
- MegaSquirt 3 V3.0 kit or V3.57 with MS3X assembled unit
- 8′ main harness or 24″ pigtail
- MS3X harness or 24″ pigtail
- JimStim + power supply
- Wideband O2 system
MS2 (assembled or kit)
- MegaSquirt‑II V3.0 kit or V3.57 assembled unit
- Two × MK‑BIP373 coil‑driver kits
-
MK‑PWMIAC (for 2nd‑gen Neon PWM idle on V3.0)
- JimStim + power supply
- Wideband O2 system
Legal/Emissions: For off‑road/closed‑course use where required. Verify local compliance and any warranty impacts before modifying engine controls.