4 posts / 0 new
Last post
Simcom module OVERVOLTAGE shutdown on OBDII power

Just got my OVMS the other day and I've been setting it up.  It's been going pretty well, and I thought I had it setup enough to connect it to my car (fiat 500e) and start reading/logging etc.  But I've run into an issue.   The simcom module will continuously loop startup due to overvoltage detection while plugged into the OBDII Port.   USB powers up just fine and reads/transmits correctly. 

Searching didn't really show me anyone else with this issue, so i'm not sure where else to go.  


After a lot of looking

After a lot of looking through the module info on github. probing points on the module with DMM and trying different stuff with a benchtop Power Supply, I found the issue. 

Symptoms were:  Modem wouldn't connect, showed essentially a boot loop in the status page.  In the Shell Page you could see the OverVoltage warning output from the simcom module.  On the module SIM Module VBAT voltage was 5VDC any time the EXTPWR voltage was 5.5V or above (any time plugged into OBDII). It was a slow ramp from 4.15v to 5.2v following input voltage ramp 5v to 14.4v.    

Then while probing around and being generally confused, I saw this.  https://photos.app.goo.gl/Rxw6YVxsPW8KRej36
The C18 Capacitor was not soldered correctly on the board.    I'm shit at SMD soldering, but got it connected and now supply voltage to the module is solid 3.995VDC. 



mgzsevrob's picture
nice find, happy that you

nice find, happy that you fixed this, when my module arrived usb port fell off, good job wasn't really needed as all can be done with wi-fi

dexter's picture
Simcom module OVERVOLTAGE shutdown on OBDII power

Thanks for sharing the issue & solution.

It's not a typical issue, but checking for soldering faults is always a good strategy with effects like this.


Log in or register to post comments