Subpage of MembersPage/BmwMFiftyTwo
When installing ECU with Motronic88 connector to the BMW M52 harness, verify the following:
ECU Unplugged
- mot88/73 is connected to main relay control pin (DVM connectivity test)
- main relay resistance = ... Ohm (fill this in, should be between 75..150 Ohm)
Ignition off:
- main relay is NOT powered
Ignition on:
- DVM DC voltage mode (+12V as a base):
- main relay control pin (same as mot88/73 verified before) measures appr -12V (if DVM black is connected to +12V).
- This mean that main relay is powered by the ECU (actually EC36/16 (p259/ch1) output, configured via MISC1 output function "always ON")
Main relay not switching ON when ECU powered, possible causes
- main relay coil not getting +12V (can be rectified locally)
- or ECU does not pull down the mot88/73
- (most likely configuration, can be rectified locally)
- or something else
- Main relay contact problem (can be rectified locally)
- Main relay faulty (can be rectified locally)
Check config
Download [.vemscfg] and compare.
- capture a short vemslog, and publish on your MembersPage
Ignition ON: (test example)
- VT is CONNECTED
- main relay is powered (0.08A)
- mot88/73 is pulled to GND via (EC36/16 = p259/ch1)
- actually configured via MISC1 output function.
If ignition is OFF (ECU does not get +12V power via M52/49=EC36/25 supply), then
- VT is disconnected
- main relay is off (0.00A)
- even though ECU is plugged in and harness is powered
- so it's not just some wire inside the ECU, main relay control pin mot88/73 is only pulled to GND when ECU is powered by ignition ON.
