Headlight problems

[Rick Norwood]

2000 GMC Jimmy 4.3L 2WD SLE I just started having problems with my automatic head lights. Started the truck the other night and no head lights. All the other running lights were good, but no head lights. The high beam lights come on but not the low beam lights. I played with every button, dimmer switch, Dome Override, and even turned off the engine and restarted, nothing. I kept on pushing buttons and nothing worked. I sat there getting pissed and then they just came on. I know there is a photocell sensor on the passenger side of the dash in the speaker but it was dark outside at the time. The Multifunction switch in the steering column was replaced once before by a dealship under warranty so it is not the original factory installed MFS but should be OEM. I did check the ground that is located under the driver's head light and it seem good and tight. Anyone seen or had this issue? The lights do seem to eventually come on, but this is a pain in the @$$.

[MT-2500]

Originally Posted by Rick Norwood

2000 GMC Jimmy 4.3L 2WD SLE I just started having problems with my automatic head lights. Started the truck the other night and no head lights. All the other running lights were good, but no head lights. The high beam lights come on but not the low beam lights. I played with every button, dimmer switch, Dome Override, and even turned off the engine and restarted, nothing. I kept on pushing buttons and nothing worked. I sat there getting pissed and then they just came on. I know there is a photocell sensor on the passenger side of the dash in the speaker but it was dark outside at the time. The Multifunction switch in the steering column was replaced once before by a dealship under warranty so it is not the original factory installed MFS but should be OEM. I did check the ground that is located under the driver's head light and it seem good and tight. Anyone seen or had this issue? The lights do seem to eventually come on, but this is a pain in the @$$.

Rick I do not have much good info from mitchell on them.
A All data online DIY SUB might help/have some good repair info on them.
I would get some one to read out and check body computer for problems.
Also connections and plug ins on it and headlight system.
And correct headlight bulbs.
Post back any body computer codes.
Also make sure sensor is open good not covered up.
Let us know how it goes.
MT

[Rick Norwood]

Thanks MT, I'll see what I can find. The bulbs are good because they eventually do light up, and I haven't changed any bulbs for over a year. I guess it is possible that something jiggled loose.

I suspect it is something to do with the Photocell. The problem is sporadic, as the low beam lights sometimes light right up when you turn the key, other times it takes a second for them to light up, and other times it takes a minute or two before they come on. One thing that I have found that does seem to work is to turn the high beams on then off a couple of times and it may be coincidence, but the low beams will come on once the high beams go off.

I can't believe that I am the poster child for things that no one has ever seen before.

[mike2004tct]

Originally Posted by Rick Norwood

I can't believe that I am the poster child for things that no one has ever seen before.

A quick fix my Dad had to do on his 2000 Buick which had the same problem;

He put a piece of tape over the sensor, to keep his lights always on.
The Dealership wanted $500.00 to replace the dash unit (parts & labor), so that piece of tape stayed on for over a year (he traded the car in last June)

He also had a faulty brake light/ABS sensor problem.
$700.00 repair bill (Again, dealer replacement- ABS unit).

Sorry, no advice.
Just wanted to let you know, you're not alone.

[Rick Norwood]

Originally Posted by mike2004tct

He put a piece of tape over the sensor, to keep his lights always on.
The Dealership wanted $500.00 to replace the dash unit (parts & labor), so that piece of tape stayed on for over a year (he traded the car in last June)

I have thought about doing the tape trick if it would work. I am wondering if the photocell unplugs and could be jumpered or just left unplugged to achieve the same thing.

[mike2004tct]

Originally Posted by Rick Norwood

I have thought about doing the tape trick if it would work. I am wondering if the photocell unplugs and could be jumpered or just left unplugged to achieve the same thing.

I'm gonna take a wild internet warrior/no experience guess and say, if you remove the plate that the sensor is attached to, remove the connector and install a jumper in it, that should do the trick.
Unless of course, it's a 3 wire or more connector.

The photocell itself is just a switch that either opens or closes the circuit dependant on light, so it may be worth a try.

Try the tape first though.

[Rick Norwood]

Originally Posted by mike2004tct

I'm gonna take a wild internet warrior/no experience guess and say, if you remove the plate that the sensor is attached to, remove the connector and install a jumper in it, that should do the trick.
Unless of course, it's a 3 wire or more connector.

The photocell itself is just a switch that either opens or closes the circuit dependant on light, so it may be worth a try.

Try the tape first though.

I'm trying to find a diagram of the Photocell circuit to see exactly what it looks like (how many wires etc.) and exactly what it is called. Any Ideas?

[MT-2500]

Originally Posted by Rick Norwood

I'm trying to find a diagram of the Photocell circuit to see exactly what it looks like (how many wires etc.) and exactly what it is called. Any Ideas?

Rick if you are going that deep in it.

A factory repair manual or all data diy online sub.

http://www.alldata.com/products/diy/index.html

[Rick Norwood]

Originally Posted by MT-2500

Rick if you are going that deep in it.

A factory repair manual or all data diy online sub.

http://www.alldata.com/products/diy/index.html

Thanks MT, here is another update. I could not find any Photocell information online because it is listed as a Sensor. A quick call to my local Dealership and found out that the GM part number is 12450120. It costs $14 USD. The unit itself has two wires and the actual sensor snaps on and off with a standard plastic clip found on just about all GM connectors. All that being said, it was not the problem. I replaced the sensor and still had the same issue with the low beams not wanting to light. I was giving up for the evening, pretty pissed that I spent the $14 and slammed the Hood shut, and the *#@&)#!% lights came on! I opened the hood back up and proceded to check the grounding wires. I found 4 different grounds, one on the negative battery cable to the block, one from the battery pigtail to the frame, another one from the second battery pigtail located under the passenger's headlight, the fourth one under the driver's headlight. All were tight and I tightened them again to be sure. The peculiar thing is that the High Beams work all the time when I pull the turn signal handle.

I am not sure if there are anymore grounding locations, any suggestions?

One thing the guy at the parts counter said was the ECM tells the headlights when to turn on and off. Where is the ECM Ground wire?

[MT-2500]

Originally Posted by Rick Norwood

Thanks MT, here is another update. I could not find any Photocell information online because it is listed as a Sensor. A quick call to my local Dealership and found out that the GM part number is 12450120. It costs $14 USD. The unit itself has two wires and the actual sensor snaps on and off with a standard plastic clip found on just about all GM connectors. All that being said, it was not the problem. I replaced the sensor and still had the same issue with the low beams not wanting to light. I was giving up for the evening, pretty pissed that I spent the $14 and slammed the Hood shut, and the *#@&)#!% lights came on! I opened the hood back up and proceded to check the grounding wires. I found 4 different grounds, one on the negative battery cable to the block, one from the battery pigtail to the frame, another one from the second battery pigtail located under the passenger's headlight, the fourth one under the driver's headlight. All were tight and I tightened them again to be sure. The peculiar thing is that the High Beams work all the time when I pull the turn signal handle.

I am not sure if there are anymore grounding locations, any suggestions?

One thing the guy at the parts counter said was the ECM tells the headlights when to turn on and off. Where is the ECM Ground wire?

Lot of grounds on ECM.
All Data online sub wiring diagram shows all grounds.
For the ground circuits you need a good wiring diagram.

Usually the body computer has first control on Day time running lights them.

Engine Oil pressure switch may work threw the ecm to body computer to tell the body computer and daytime running light module the engine is running or not running.
Also park brake light switch is tied in there to.

[MT-2500]

ON ECM grounds look for the black wires.

C1 pin 17/18
C2 pin 17/18

ECM grounds are connected to/grounded to black ground wire Right rear cylinder head

[Rick Norwood]

O.K. here is another piece of information. The lights coming on after slamming the hood got me to wondering about the Headlight Relay. The Relay/Fuse panel is located over the driver's wheel well inside of the engine compartment, just under the hood, which I think would be probably be jostled around when the hood is slammed. I opened the cover and it appears that the Headlight Relay is located at the front of the panel, closest to the radiator. The diagram inside the cover of the panel shows a relay marked HDLP PWR. I assume this means HEADLAMP POWER. I tapped on in and wiggled in its socket but I decided to see about a replacement before trying to remove it (and possibly break it). Here is the funny thing, since I did this on Friday afternoon, the headlights have worked properly and not given me anymore trouble. I talked to a parts guy at the local parts store and they did not have any replacement relays, but he did say that traditionally, relays are either good or they are bad and there is no sporadic function with these things. Well I don't know, considering that I am a poster child for things that no one has ever seen before in the entire history of automobiles, I am hoping that my problem was a dirty socket or some other minor issue, but for now, I am going to keep a close watch on this and see what happens.

[Rick Norwood]

Well, I knew it was too good to be true. Last night and again this morning I had no headlights when starting the Jimmy. In both cases I carefully opened the hood with the motor running and lightly tapped on the headlight relay and instantly, the head lights came on.

What I don't know is whether I have a bad relay or possibly a dirty socket. I guess I will stop at the dealership on the way home from work and pick up a new relay.

Can any of you tell me anything about these relays? I have heard of fuel pump relays going bad, but any info is goodness.

[mike2004tct]

On my '97, I have 3 relays on the firewall in the engine compartment.
Is the unit you're talking about in this area?

I also have two or three behind the cover in the glove box.

If so, try swapping them out with each other if they are similar types, and see if the problem moves with the relays.

As far as stating earlier they either work or don't work, not necessarily. It could be a short or weak connection in the coil, which when energized, either opens or closes the relay (dependant on the type: normally open or normally closed).

[Rick Norwood]

Originally Posted by mike2004tct

On my '97, I have 3 relays on the firewall in the engine compartment.
Is the unit you're talking about in this area?

I also have two or three behind the cover in the glove box.

If so, try swapping them out with each other if they are similar types, and see if the problem moves with the relays.

As far as stating earlier they either work or don't work, not necessarily. It could be a short or weak connection in the coil, which when energized, either opens or closes the relay (dependant on the type: normally open or normally closed).

On the 2000 Jimmy SLE, there is a fuse/relay panel containing a half dozen or so relays and about a dozen fuses that is located above the driver's side wheel well and almost touches the hood when it is closed.

Based upon your comment that there could be sporadic issues, I will see if I can get a new one and keep my fingers crossed.