No headlights on a 2000 Grand Cherokee

[cLAY]

My FIL picked up a 2000 GC, shortly after acquiring it one headlight went out, he replaced the bulb and when he went to try it after putting it back together neither worked.  I've checked and there is no power at the plugs.

I'm guessing its the DRL. If its just unplugged will the lights works or is some rewiring needed? Any other suggestions to check? Where is the DRL?

High beams work fine, just no low beam or DRL.

[Dingleberry]

With the module removed, the headlights will work just fine (did this on my XJ). However, if you then find that your highbeam indicator is not lighting up on the dash, you have to jump pins 1 and 4 together on the module's connector to get it working again (as per last paragraph on this page http://jeep-xj.info/HowtoHeadlightLoom.htm )

[morerpmfred]

Low beam fuse or low beam relay. One of the low beam bulbs may be shorting out.

[cLAY]

Hmmm. Been doing some reading and it looks like it's not so simple. On the WJs the DRL is controlled by the BCM and a special relay. The regular low beam relay is replaced by a different relay that pulses the voltage to the headlights for the DRL function when called for by the BCM. Then when you flip the lights on it sends a steady 12v signal to the lights. 

I've found lots of posts by frustrated owners trying to install HIDs and having burn out modules and flickering lights from the pulsing voltage being sent.

Pulling the relay results in no low beams. Replacing the relay with a regular 'US' model will only work if you have the dealer reprogram the BCM to 'US' model.

Might have to break down and get a new relay.

And yes the fuse is good.

[cLAY]

Alright here is what I found and what I did. Hopefully if someone else has this problem or tries to wire up some HIDS this will help.

Tested the DRL relay/module and found no power signal coming from the BCM to kick the low beam relay. it was recieving a swtiched ground signal from the BCM.  Reports that I read online indicate that this is a common failure of the BCM.

Not wanting to take this old beater to a dealer I wired around the BCM. Attempt 1 was to simply supply 12v to the DRL/Low beam relay, this resulted in smoke and a melted wire. Opps,

2nd attempt.  The hi beams still worked fine and used a 5 pin relay. I tapped power from the 87apin and ran it to a regular 4 pin relay. Then I ran wires from where the DRL relay for battery power, power out to lights, and the grnd signal from the BCM.  When I turn the key on power goes from the #87a pin on the high beam relay to the #86 pin on the new low beam relay. Turning the headlight switch on sends a grnd signal from the BCM. out  #85 to the #85 pin on the relay causing it to close and power the lights.  Turning on the high beams causes the hi beam relay to close, opening the connection to 87a and causing the lows beams to go out,

Its butch but it works.   

[Dingleberry]

Nicely done!

I guess these new damfangled vehicles be using complicated computermetronics

[cLAY]

Yep its getting stupid.

One of the Fords I worked on at work had to have the DTC codes cleared after repairing a a shorted turn light in order for the circuit to work again. The BCM saw the short and locked out the circuit to prevent damage. Smart, and annoying.

[Dingleberry]

all this "smart" technology just ends up being dumb in the real world, when it breaks and prohibits other functions/features from working at all.