The Official MegaSquirt FAQ by 03neonRT

By diyauto
( 1 )

3 minute read

The Official MegaSquirt FAQ 

Compliments of 03neonRT @


1. What is MegaSquirt?

MS is a full standalone fuel and spark controller. MS can completely replace your stock PCM, however you will need additional relays and wiring etc. to power all of your accessories. For this reason most people used the stock PCM to power all the accessories and sensors, while MS takes over engine control.

2. Where can I get one?

A list of all current vendors can be found here: You can buy the MS unit prebuilt, or get an unassembled kit and do it yourself. It is not hard to assemble the MS, even if you have not had much experience with electronics. If you are patient, not afraid to learn, and willing to do a little (or a lot ) research, then you have what it takes to build and install a MegaSquirt system.

3. Ok great. Where do I start?

First things first. Read the FAQ on found here:

Then read through the MegaManual. This contains all the details of how the MS works, assembly instructions, setup and install guidlines, tuning, wiring... it's all here:

Since most of us 2gners will be using the MSnS-E "extra" code (the only code that will run fuel and spark on Neons), the MSextra manual will also be very informative:

4. Specifically, what do I need to run MS on my Neon?

Option A: Unassembled kit (recommend

- MS1 v3.0 pcb
- Two VB921 high current ignition coil drivers (most kits come with one VB921 included, so you may just need to get one additional transistor)
- GM IAT and CLT sensors
- Wiring harness
- Stimulator (for powering and testing your MS before hooking it up to your car)

Option B: Prebuilt unit (recommend

- When ordering the ECU from rs-autosport specify the follow options:

Configuration: Neon/420A
Fan control output: No (assuming stock ECM still controlls radiator fan)
Firmware: Latest stable release of MSnS-E
Map sensor: Your preference
Tachometer signal output: No (assuming no additional tach signal is needed. i.e. you're not adding any other hardware that requires a tach signal).
Upgrade to MegaSquirt II: Standard MS-1 controller

You will still need:

- GM IAT and CLT sensors
- Wiring Harness
- Stimulator (optional)

5. Firmware

The latest version of MSnS-E firmware can be downloaded here: by clicking "download latest". This link also cantains all the info about the features of the "Extra" code and info about the Neon Crank Decoder, as well as hardware modifications required to control the coilpack. (the site says for pre-NGC Neons only, but MS will work on NGC cars and read the NGC crank trigger wheel)

The NGC code can be downloaded here:

FAQ Created by "turbodudey"