service engine light after changing headlight assembly

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Hi,
I bought a new complete headlamp assembly for my 04 Rendezvous and my service engine light came on immediately after changing.
It only comes on in the daytime.
After dark, it is fine. I have replaced the bulbs to be sure they are all the same and all the lights do work as they should.
It's just when the vehicle is started in the daytime, as soon as I put vehicle into drive (which would activate the daytime lamps) the service engine light comes on.
This is a Canadian vehicle, so daytime running lights are the law.
Appreciate any input as I am stumped.
Also there are no error codes, even using a tech2 tool when the service engine light is on ???
 

lrj975

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02 Rendezvous CXL 1-owner
Is your DRL working or not? you mention all lights work as they should but then mention DRL are the law implies to me that you're concerned you're driving around without DRL.

or is the issue just with the CEL turning on and everything works?

DLR turns on with ignition on, parking brake not set or transmission not in park, and ambient light sensor detects daylight.

If the BCM detects voltage issue with control circuit of the DLR relay coil, or the DLR relay, DTC B2602 / B2603 are set and stays in history, and CEL goes on.

Was this actually properly diagnosed with a techII? A techII can also command the BCM to activate the DLR.

Why was the headlight assembly replaced, was there an accident, maybe a wiring harness was pinched or pulled and getting shorted. Was there a wiring meltdown?
 
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Hi,
The reason for changing the light was that when I went to replace a bulb, the back of the assembly broke off.
I'm not sure if the DRL is working properly now as the dash lights also come on in broad daylight when I put vehicle in drive, I'm pretty sure the dash lights didn't come on before.
This issue began within seconds of replacing the light assembly and putting the car in drive.
With the service engine light on, the garage up the street couldn't find any error codes.
I'm pretty sure it was a tech2 he was using.
Dumb question ... what is the CEL?
To stop the service engine light from coming on in the daytime, I have placed a cap over the light sensor.
Appreciate any advice.
 

lrj975

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02 Rendezvous CXL 1-owner
DLR is high-beam headlamps (the 2 inners, adajacent the grill) on at half voltage.. DLR is activated when ignition on, parking brake not set or transmission not in park, and ambient light sensor detects daylight. (and of course if headlights are manually turned on.)

Any one of those things negated will turn off DLR. So by covering the ambient light sensor, the DLR is turned off and thereby turns on regular headlights (the 2 outer headlights) which also turns on the dashboard lights. That's why your dashboard lights are coming on now in the daytime. That is actually a good test that all that is working.

So problem occurs when attempting to enable the DLR (again.. ignition on, parking brake not set or transmission not in park, and ambient light sensor detects daylight.) and the high-beams don't turn on at half brightness, and CEL (check engine light) turns on. Instead of DLR activating, the BCM (body control module) detects a problem with the DLR circuit, throws a code (like B2602) and illuminates CEL. I would bet the shop wasn't correctly reading your codes. He would need a really good scan tool that reads BCM for GM cars. The cheap scan tools can just read the PCM (powertrain control module). Sounds like the shop just tried to pull codes and not really diagose further.

Can you confirm the high-beam headlamps both work ok? I would suggest going back to the high-beam lamps, remove and check the sockets, wiring harness, maybe something got crossed-up during the installation. And try another shop to get the CEL codes scanned, check for codes stored in history.
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Hi,
The company I bought the headlamp assembly from has sent out a new one to me. I hope when I switch them again, the problem stops. Otherwise, I guess I will have to take to dealer.
As I said earlier, it just seems odd that everything worked pefectly until exactly the minute I put this new unit in.
Dealer costs to check it out cost almost as much as the unit did.
I really appreciate your input and will update this post when I try the new one and it works fine or whatever the dealer my find.
 

lrj975

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there's a fuse for DRL in the underhood block, number 14

check that maybe it blew

if that's good then relay 53 controls DRL, give it a slight tap and try it again, or just replace it, it's a cheap part to throw at it $10 (ACDelco# D1780C)
 
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Hi,
Fuse 14 is good.
I taped relays 52 and 53 as owners manual shows 52 as (DRL) and 53 as Low Beam Headlamps.
When started car again, the service engine light came on immediately and the outer lights came on without even taking vehicle out of Park. As soon as I put in drive, all 4 healights came on and the high beam switch was in the off position.
Crazy that now the outer lights are on instantly and all I did was tap both relays.
Suggestions.
You have been more then helpful.
 

lrj975

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indeed 52 is DRL, 53 is low-beam headlamps, 55 is high-beam headlamps.

They all have a part in the DRL circuit. again.. ignition on, parking brake not set or transmission not in park, and ambient light sensor detects daylight so anything that changes those conditions, like turning on headlights, transmission put in park etc, cancels the DRL, so all those relays are involved.

Suggest replace 1 or all of 3 of those relays, start with 52.
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Final update,
I changed relay 52 and the lights are now working so far as they should.
I can't believe 2 `mechanics' here looked at and not one said anything about it possibly being thew relay.
Many thanks for your help Irj975
Have a great day
 
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Update:
Hello again,
I'm sad to say that the problem is back again. I changed all the relays and even put in the replacement headlight housing that was sent to me in case the first one was the culprit.
I have finally given up and have made an appointment at the dealer.
Sorry I took out my original one in the first place.
Unfortunately for tax and other reasons, it is in a dump somewhere in Minnesota.
 

Salvaing

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g_152218

someone has to have a solution to this, is it possible the GM wiring harness has a capacitor or something in the wiring allowing the highbeams to get half voltage while the drl is on?
 

Salvaing

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Its more complicated.
When the BCM receives ambient light sensor (sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level) it will either turn on the daytime running lamps (DRL) or the headlight relay for auto headlamp operation.
Any function or condition that turns on the headlights will cancel the daytime running lamps operation.
The daytime running lamps (DRL) illuminate the high beam headlights at a reduced intensity.
With the headlight switch in the OFF position, the headlights will either be turned ON or OFF, after an approximate 30 second delay depending on whether daylight or low light conditions are sensed. Voltage is applied at all times to both the switched and coil side of the DRL relay.
When the ambient light sensor detects a low light condition, the BCM applies a ground to the DRL relay control circuit. This energizes the relay and applies voltage to the DRL fuse.
Current flows from the DRL fuse to the right high beam lamp to the left hand high beam lamp.
The high beam headlamps are now in series, and split the voltage.
The headlamps illuminate at half intensity.
The ground is provided from G101.
The DRL operate when the ignition switch is in the RUN position, and the parking brake is not set or the transmission is not in park.
When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.
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