TDM900 : ECU CO Mode

The adjustment of the idle mixture is one of the engine operation parameters controlled by anti-pollution standards (EURO2 / EURO3). Compliance with these standards requires a lean mixture corresponding to less than 1% of CO (carbon monoxide), while the requirement of a better driving capability involves a richer mixture with a CO level of around 3%.

The TDM900 ECU offers the ability to adjust the CO setting from the dashboard. This setting will actually enrich or lean the air / fuel ratio, by adjusting the injectors pulse width control.

A CO measuring instrument is normally required to check the CO level in the exhaust gas. Refer to the Workshop Manual for a complete description of operations.

In case no CO measuring instrument is available, all that can be done is an empirical adjustment based on the engine behavior, essentially by enriching the mixture.

It is strongly advised that you perform the following operations beforehand :
• Checking the valve clearance.
• Setting the idle speed.
• Synchronizing The throttle bodies.


1 - Clock
2 - Odometer
3 - SELECT button
4 - RESET button
5 - Engine control light

Going to the DIAG Mode

Starting condition : main switch is in OFF position.
1 - Press the SELECT and RESET buttons
2 - Turn the main switch to the ON position while keeping the buttons depressed.
3 - Keep the buttons depressed until the display change and DIAG appears - this takes around 8 seconds.
4 - Release both buttons.

Switching between the DIAG Mode & the CO Mode

1 - Press the SELECT button in order to switch the display to CO.
2 - Simultaneously press the SELECT and RESET buttons for two seconds or more to select an item.
3 - C1 appears on the clock display : Cylinder #1 is selected.

Switching between the cylinders #1 & #2

1 - Press the SELECT button in order to select the cylinder (C1 or C2).
2 - When the required cylinder number is showing on the display, simultaneously press the SELECT and RESET buttons for two seconds or more.
3 - The current CO value for the selected cylinder is displayed (eg. "9").

Changing the volume of carbon monoxide in the exhaust gas

1 - Press the SELECT button in order to increase the number up to 128 = RICH mixture.
2 - Press the RESET button in order to decrease the number down to -128 = LEAN mixture.
3 - Simultaneously press the SELECT and RESET buttons to memorize the new value and return to the cylinder selection mode (step C).


End of procedure

To finalize, turn OFF the main switch.

Tuning advices

• The engine can be started while accessing the CO mode.
• Each engine is different and has its own set of CO factory setting.
• It is therefore useless to compare CO settings between different machines.
• The factory setting gives a minimum CO level and so is rather poor.
• There is usually a difference (about 10) between the cylinders.
• Do not modify the CO level unless you have good reasons to do so. Playing with the dashboard is not a good reason.
• Before proceeding with the CO setting, always write down the initial values.
• Proceed with small changes (eg 5), write down new values and test ride.
• CO setting may also be adjusted by optimizing the idle speed.
• A too rich mixture results in a rise in fuel consumption.
• A too lean mixture results in a rise in temperature of exhaust gases. This is reflected visually by a blue stain on the exhaust pipes.

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