Think my BECM has started playing up....any tips re where to look first?

jerrytlr said:

OK new fault for today... they do seem to be appearing faster then I can fix them at the moment :-(

I get

- 'LHF door open' and 'electrical fault..... check handbook' on the message display
- main beam not working
- sidelamp warning light on dash always on
- no electric windows or interior lights
- Nanocom can't talk to BECM ECU

.... so am assuming I have a BECM problem.

According to Nanocom, I have 13.5V when engine running, battery is almost new.

Any suggestions re where to look first, or is it just a case of

- check fuses
- check connections to BECM under seat

Could it be due to dreaded fuse box under bonnet corrosion problem?

TIA for any pointers

Cheers,

Jerry

Click to expand...

jerrytlr said:

Thanks Keith

Following a bit more investigation this morning...

1) charging is around 13.8V, measured using DVM across battery, also tried my alternator tester (also basically a voltage meter!) which rated output as between 'good' and 'strong'.

2) Have been trying to get my head around RAVE electrical troubleshooting. Tested connections C105, C165 and C107 and all have good voltage present, also tested the earth connection on BECM which is adjacent to those connections, continuity to car body seems OK.

3) Unbolted fuse box under bonnet, ensured all connectors properly seated. There seems to be no corrosion at all, all looked in good condition


So, I am a bit stuck. Have disconnected battery and will see if leaving that disconnected for a while sorts it out.

It does appear to me as though the BECM has gone into some sort of fail safe mode, the car is still driveable but lots of ancillaries are not working properly.

If only the Nanocom would talk to it................


Are there any other connections I should inspect/test? Are there any other +12V feeds to the BECM other than the three I have tested?

I am trying to avoid removing the seat but will if necessary!

Cheers

Jerry

Click to expand...

jerrytlr said:

Thanks Keith

Following a bit more investigation this morning...

1) charging is around 13.8V, measured using DVM across battery, also tried my alternator tester (also basically a voltage meter!) which rated output as between 'good' and 'strong'.

2) Have been trying to get my head around RAVE electrical troubleshooting. Tested connections C105, C165 and C107 and all have good voltage present, also tested the earth connection on BECM which is adjacent to those connections, continuity to car body seems OK.

3) Unbolted fuse box under bonnet, ensured all connectors properly seated. There seems to be no corrosion at all, all looked in good condition


So, I am a bit stuck. Have disconnected battery and will see if leaving that disconnected for a while sorts it out.

It does appear to me as though the BECM has gone into some sort of fail safe mode, the car is still driveable but lots of ancillaries are not working properly.

If only the Nanocom would talk to it................


Are there any other connections I should inspect/test? Are there any other +12V feeds to the BECM other than the three I have tested?

I am trying to avoid removing the seat but will if necessary!

Cheers

Jerry

Click to expand...

jerrytlr said:

Thanks Keith

Following a bit more investigation this morning...

1) charging is around 13.8V, measured using DVM across battery, also tried my alternator tester (also basically a voltage meter!) which rated output as between 'good' and 'strong'.

Click to expand...

jerrytlr said:

OK will check the alternator output, thanks all

Disconnecting the battery appears to have worked; the BECM seems to have reset itself and now all is working OK again. Could be feeble alternator output that caused it to go in the first place so still worth checking I think.

Cheers,

Jerry

Click to expand...