Where does DME get power from?
 

On late model 944s, 968s...where does the power come from? Directly from the battery? Ignition Switch? Or?

Harvey

Ignition switch

AFJuvat

Thank you!

Really? Then why does it have a DME relay???

http://www.*****************.com/product_p/pp993.615.227.00.htm

Should also have one of these that tend to go bad:

http://www.*****************.com/product_p/pp928.602.706.01alt.htm

I stand corrected.

The DME relay gets its power from the battery

The ignition switch closes the DME relay, powering the DME.

Happy?

AFJuvat

You're scaring me Mike! I hope this was a senior moment.

I knew I shouldn't have huffed all of that carb cleaner this morning....


AFJuvat

OMG this is a sad day. Mother Juvat is indeed human...... :(

There are kittens crying throughout the world as we speak.

SmileWavy

Yeah... I suck.

AFJuvat

Back to the question. What should have power with the key on.

The injectors and the coil/ignition module.

If there is no voltage to the coil then the ignition switch is not working/bad.

If there is voltage to the coil but not the injectors then the DME relay is not engaging.

If there is voltage to both then the DME is getting it's 12 volts along with the injectors (same circuit). Check that the fuel pump is working during cranking. This tells you that the second set of contacts in the DME/fuel pump relay are being pulled in by the DME as it sees the control voltage going to the starter.

You can check wither the DME is reading the flywheel sensor by getting a NOID light and seeing if the injectors are pulsing. No sensor signal no pulsing.

Report your findings.

Also need to check the alarm as this will remove power from the DME too.