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Bosch 0227100203 ignition module: Going high or going low?


Sep 3, 2017
I am testing the MS2 I built into my 940.

I think I just fried my ignition module during the spark testing.

Wanted to test the spark using the tunerstudio test mode, and it did work.
However my ignition module got extremely hot very quickly. (touching it HURT)

Now it does not produce a spark anymore.
I had the logical signals from the ecu configured as "going low".

What should my configuration be using the Bosch/Huco 203 module? Going high or low?
Can't find it anywhere online.
Did I fry it this quickly or did I mess up something else?

Additional info:
Wasted spark ignition.
Using the Bosch 0 221 503 407 2x2 motorsport coil.

Kind regards, Frank
Did you find the BOSCH specifications in their online docs? I don't know that it specifies what you seek, but it was chocked full of tech. spec. data.

I know the transistors in the 203 power stage get quite hot.... the reason they need proper heat sinking paste, the factory design with fender air flow on the back side of the aluminum base.

If the document is NLA, shoot me a PM and I can send you that information. I'm still LH2.4 but running the infamous BuchkaSpark and using the 203 and likely the same motorsport coil setup.
It depends on how the MS2 is built

When using standard ignition modules, if you tap the spark outputs off of the MS LEDs using resistors, you want "Going Low" (the LEDs and resistors invert the signal from the CPU). If you add a buffer chip, e.g. TC4427, you want "Going High". Check the MS2V30_Hardware pdf to make sure I'm remembering this correctly.
Thanks for the replies guys.

To further clarify: When I set my MS to "going low" the ignition output signal is 5V, and it grounds when it should spark.

Wheter this is OK depends on the transistor type used in the ignition module if I'm correct?

If I have it reversed it means the transistors are switched "on" most of the time instead of small spikes?
This could possibly explain the meltdown of my module.

For several Bosch modules I have found that "going high" is the type of input signal that is needed, however for the 203 I did not find this data.
I will receive a new module to test soon and will keep this updated. :lol:
Yes, but it's a little more confusing.

MS uses the Going Low (or what I think of as charging when high) for the original setups that included a single coil drive transistor within the MS box. For high current drive transistors, NPN transistors are more efficient than PNP. This means that most, and maybe all, ignition drive transistors are NPN. To charge the coil, drive the base high. To spark, drive the base low. Hence the "going low" terminology. (When base is high, the transistor output is near ground, which allows current to flow from the +12v coil connection, through the coil, to ground.)

If you use resistors off the LEDs in the MS box, the LED circuit inverts the signal and you need to use the opposite polarity setting in MS.

For logic level COP coils, without a separate ignition module, the polarity may vary by coil model.
5.3.3 of TFM says "Set the Spark Output to Going High. Build circuit in" is the FET method which has certain advantages

"With this wiring the Spark output must be set to "Going High".
Can drive most logic coils including low resistance VAG COPs.
Coils do not receive a spurious signal pulse at power on.
Uses standard "Going High" setting."

The resistor method I do not reccomend has concerns.


Coils receive a spurious pulse at power on.
Cannot drive some VAG COPs."

The "VAG COP's" is VW Audi Group Bosch igniters, not just COP's.
These igniters have a lower input impedance and the resistor method will not always adequately trigger (or will stress the MS circuits) when using these modules.
The FET method is desirable as it will run anything you connect to it and you will not get spurious sparks when the ignition is turned on and off.

I was firmly told that the "going high" and "going low" terms apply to the processor output, not to the signal actually presented to the module by whatever method is used.
The circuit built determines the correct polarity.
I have found that following the recommendations produces the best results and although it seems the resistor method works it is not recommended for that Bosch igniter.
The clincher for me is the FET method eliminates spurious sparks.
A little update: I just tried the H?co 138401 (e20). I have it mounted on a 1cm thick aluminium plate, using conductive paste.

Setting in MS: Going low.

Sparks both channels, works well. However, it still becomes very hot after only a minute of testing. Normal?