In case of ignition problems, the following error messages are recorded:
2E18 ignition, cylinder 1
2E19 ignition, cylinder 2
2E1A ignition, cylinder 3
2E1B ignition, cylinder 4
2E1C ignition, cylinder 5
2E1D ignition, cylinder 6
The following should be taken into account:
- if DME considers, that everything is ok with the management of the ignition coils and tries to ignite the fuel mixture, but don’t succeed, the error messages regarding misfires (29CD .. 29D2) will be recorded in the error message memory;
- if DME sees, that there is a problem with the management of the ignition coils, the error messages regarding ignition (2E18 .. 2E1D) are recorded.
If DME has identified problems with the management of ignition coils (the error messages regarding ignition are recorded), at first the problems with the DME periphery have to be solved. It makes no sense to check ignition coils and spark plugs (solve problems with misfires), if DME has detected, that the spark is not “created” at all.
How does DME control the management of the ignition coils?
Here, the schematics of the control of the ignition coils management transistor (ignition):
Here, on PCB R1 (resistors, which help to measure the voltage in the primary side circuit of ignition coils):
Via voltage divider of resistors R1/R2, CPU measures the voltage in the primary winding of the ignition coil. If the management transistor of the ignition coil works properly and the connection of the ignition coil is good, after the closing of the transistor (in the moment when the ignition coils start to release acquired energy on load – to the spark plug), the voltage spike is detected on its C. This voltage spike is checked (and for MSD85 – also measured its length) by CPU.
In the image: a closing moment of the transistor is marked with an arrow, the period of the positive spike is marked with an oval.
Unfortunately, the manufacturer doesn’t give more exact information, how the DME measures the ignition parameters.
My observations:
- MSD80 performs only identification “ignition successful/unsuccessful”, it means checks the existence of the positive spike for time X after closing of the transistor;
- MSD85 already measures the length of each ignition cycle, it means it can detect the not only correct performance of the electrical circuit but also identifies misfires and partly misfires. True though, these ignition data are available in the practically unusable test block;
- MSD87 applies the corrections of the injectors till 1500RPM, based on the changes in the rotation of the flywheel; according to this, it seems that the flywheel is used also to detect misfires (as for MSD80).
Here, the example of the appropriate error message of MSD80:
Marked with red: 0ms ignition time – voltage spike on the management transistor C is not identified.
If the error messages regarding ignition are recorded in the error message memory of DME:
- check the connection of the ignition coil. Unfortunately, the plugs of the ignition coils and their fixation mechanisms are defective. The fixator serves only as a decorative element, the plug “works” only in two last mm. So you have to make sure carefully if the plug is properly pressed;
- if there is no problem in the ignition connection, check the ignition management transistor, using an oscilloscope (controlling the voltage on the ignition coils) or multimeter (checking the short circuit of the B/E and C/E transitions of the transistor).
Correct voltages on transistor C (the oscilloscope with Samplerate at least 5MHz has to be used for measuring);
- voltage in closed condition: +12V (onboard voltage) [1];
- voltage in open condition: +1 .. 2V [2];
- voltage spike after closing of the transistor: till +350 .. 380V for the first 5 .. 10us [3]; around +25V for next 2ms [4].
If the B/E transition of the transistor is damaged (it is possible, “thanks” to the built-in overvoltage protection of the transistor), in case of connected DME on its C (accordingly – also the ignition coil) the voltage will be +12V for all the time.
If the transistor has a short-circuit of the C/E transition, on C of the transistor (also on ignition coil) all the time will be the voltage of 1 .. 2V, the ignition coil will heat up intensified.
If the transistor has the damage of the Zener diode of the overvoltage protection, on its C could be the voltage of 3 .. 5V in its closed condition (voltage spike – won’t be, not even taking into account as if the correct voltage in the open condition of the transistor).
In case of damage to the ignition coil transistor, the damage of the management IC of the transistors is possible.
