Swapped ECM still no headlights

[olddaddy]

Like a lot of folks I've had ongoing trouble with my low beam headlights on our 2000 V40. I've replaced them thinking they burned out quickly only to discover that the problem was probably the relays in the ECM. Since both lights went out over the weekend I pulled the spare ECM off our 2001 S40 parts car. I made the swap into the V40 and still no headlights......so I am completely lost, as always with this car. Assuming the swapped ECM is not also defective, what else would make both headlights not come on? They were intermittent over the past few weeks, one would be on and the other off, now both are off. Should I be buying relays to solder into the original ECM? Could there be an issue with the switch on the dash? The dip switch stalk on the column? My love/hate relationship with this car continues to swing wildly from side to side...

[gatos]

First of all, it is called CEM. ECM is also referred too as ECU and it's a different thing. If the spare CEM is working fine on the 2001 car, then it's not faulty. Have you checked if there is any voltage at the headlight connectors? Do you get lights on the daylight bulbs and your high beams? Are your rear lights working?

[olddaddy]

Sorry about the ECM/CEM mixup it's late and I've reached my daily limit. The tailights are working as are the side marker lights and high beams. The low beams or daylight lights are not coming on. I have not checked for voltage at the connectors, but will do so tomorrow.

[gatos]

No worries. I did the same mistake a long time ago too....

As I said before if the CEM on your 2001 car is working fine on the 2001 car, then you have another problem with your car. Either a faulty headlight switch, or worse case scenario corroded wiring loom under the radiator.

A very common symptom of a failed CEM is that when you test the voltage across the headlight connectors, you get 12V as expected. However, when you fit a bulb, it does not work.

[olddaddy]

A followup from last evening......I pulled the dip beam bulbs out of the housings and discovered I have the dreaded crumbling connectors. One was completely gone and the spade connectors were loose. The other was cracked and I could see evidence of arcing on the spade. I managed to crimp the connecters down tighter so they hold the spade better. I also replaced the bulbs and behold, there was light! So, I've ordered replacement connectors and will install them over the holiday. I hope this will solve or at least delay the problem for awhile so I can dwell on the many other problems this car has. Thanks Gato for the insight and replies, all are appreciated.