Output Test Mode

Only for use with the MS2-Extra code (HC9S12C64 based microprocessor - MS2 Daughter Board)


Please Note:

All of these instructions / diagrams are to be used at your own risk, like most things there is more than one way to do the same thing, what we have tried to do is to offer a method that we have tested or that others have tested for us. No warranty expressed or implied.

Use at your own risk.



The output test mode allows you to test the injectors and coils connected to your ECU without the engine running. This can be used for fault finding or tuning your settings such as injector PWM or ignition coil dwell.

BE CAREFUL : The test mode allows complete control over the outputs, so be especially careful not to flood your engine with fuel by opening the injectors or melt your ignition module with incorrect dwell !

To start, open your tuning software and go to the Advanced menu and select Output test mode

Then you will see the menu:

This particular sequence is required to prevent the potentially dangerous test mode being engaged by accident. Even though you have hit burn, this value is not saved to flash and will return to zero. Note that once you have finished with test mode, turn you Megasquirt off.

Coil Testing

Coil testing allows you to confirm that your coils are working correcting, are wired as you expected and experiment with dwell settings.

Remember that the output from a typical coil can be around 30kV which HURTS and could be fatal. Pacemakers or other similar devices could be interfered with. If in doubt do not use.

Start with low dwell numbers and work up if testing. In this mode, the dwell figure is the absolute time used – it is not adjusted for battery voltage. The dwell number entered into the normal settings is the 14.4V (normal alternator voltage) nominal dwell.

Injector Testing

Injector testing can be used on an injector test bench, or with injectors mounted on an engine. On the test bench a non-flammable test fluid is typically used. When testing on an engine, be especially careful that you do not inject fuel and flood your engine. To safeguard against this you should de-pressurise the fuel system. Either physically by releasing the hose unions, or if you run your engine at idle and disconnect the fuel pump the engine will run until the fuel pressure is consumed. You must still be very careful if fuel is around as residual fuel can cause serious explosions. (i.e. if you used the injector tester first and then used the coil testing you are at risk.) After testing on an engine it is advisable to crank the engine for say 30 seconds with the coils and injectors unplugged to purge the engine.

When you have finished testing, close the menu and turn the Megasquirt off, then back on again to resume normal operation.

If you have a question, comment, or suggestion for this FAQ please post it on the forum.
Last Updated: 05/25/2007 16:43:04

No part of this manual may be reproduced or changed without written permission from James Murray, Ken Culver and Philip Ringwood.