2004 canyon signal lights only work with high beam on

Bright lights wont shut off ? Assume you mean high beams ? Reading how they work might thing high beam relay has stuck contacts inside .

Headlamps
The headlamps may be turned ON 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC, the headlamps will be OFF in daylight conditions, or low beam operation in low light conditions. Battery positive voltage is supplied to the low beam relay and the high beam relay in the underhood fuse block. When low beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the low beam relay. This activates the relay and the relay supplies voltage to the left hand low beam headlamp through the LH LOW BEAM fuse and to the right hand low beam headlamp through the RH LOW BEAM fuse. Ground for the left hand low beam headlamp is provided at G101. Ground for the right hand low beam headlamp is provided at G102. When high beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the high beam relay. This activates the relay and the relay supplies voltage to the left hand high beam headlamp through the LH HIGH BEAM fuse and to the right hand high beam headlamp through the RH HIGH BEAM fuse. Ground for the left hand high beam headlamp is provided at G101. Ground for the right hand high beam headlamp is provided at G102.

Likely a bad ground, but could be a fuse(s), or a failed multifunction switch, or BCM. It requires circuit testing to identify the cause.

Your best bet , take your vehicle to a qualified repair shop . Before you want to replace the BCM . . Professional tech would check for DTC'S - diagnostic trouble code's in the BCM before replacing part's that are not needed .

No signal at signal wire on relay ???? Which circuit wire mite that be ? Hooking up a factory or professional scan tool to view input data from the switch would also be a good step .

Headlamps
The headlamps may be turned ON 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC, the headlamps will be OFF in daylight conditions, or low beam operation in low light conditions. Battery positive voltage is supplied to the low beam relay and the high beam relay in the underhood fuse block. When low beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the low beam relay. This activates the relay and the relay supplies voltage to the left hand low beam headlamp through the LH LOW BEAM fuse and to the right hand low beam headlamp through the RH LOW BEAM fuse. Ground for the left hand low beam headlamp is provided at G101. Ground for the right hand low beam headlamp is provided at G102. When high beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the high beam relay. This activates the relay and the relay supplies voltage to the left hand high beam headlamp through the LH HIGH BEAM fuse and to the right hand high beam headlamp through the RH HIGH BEAM fuse. Ground for the left hand high beam headlamp is provided at G101. Ground for the right hand high beam headlamp is provided at G102.

Headlamps Inoperative - Low Beams
Step
Action
Yes
No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference: Master Electrical Component List
1
Did you perform the Diagnostic System Check - Vehicle?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Vehicle
2
Place the headlamp switch in the HEADLAMP position.
Place the headlamp dimmer switch in the LOW position.
Do the low beam headlamps illuminate?
YES - Go to Testing for Intermittent Conditions and Poor Connections
NO - Go to Step 3
3
Disconnect the turn/headlamp switch connector C2.
Connect a 15-amp fused jumper between the headlamp low beam signal circuit and a good ground.
Do the low beam headlamps illuminate?
YES - Go to Step 4
NO - Go to Step 5
4
Inspect for poor connections at the harness connector of the turn/headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
YES - Go to Step 7
NO - Go to Step 6
5
Repair an open or high resistance in the headlamp low beam signal circuit. Refer to Circuit Testing and Wiring Repairs .
YES - Did you complete the repair?
NO - Go to Step 7
--
6
Replace the turn/headlamp switch. Refer to Turn Signal Multifunction Switch Replacement .
YES - Did you complete the replacement?
NO - Go to Step 7
--
7
Operate the system in order to verify the repair.
Did you correct the condition?
YES - System OK
No - Go to Step 2

It's more then likely the dimmer switch .

DTC B2575
Circuit Description
The body control module (BCM) turns on the LOW BEAM relay when the ambient light sensor senses a dark condition or the low beam headlamps are requested ON. Battery positive voltage is supplied to the LOW BEAM relay at all times. The BCM grounds the LOW BEAM relay control circuit in order to activate the relay.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2575 Headlamp Control Circuit

B2575.01
Will set if there is a short to voltage in the low beam relay control circuit.
B2575.06
Will set if there is an open or short to ground in the low beam relay control circuit.

There isn't one. There's two fuses for the turn signals. The flashing is controlled by the Body Control Module.

http://www.stockwiseauto.com/product_info.php/products_id/324058/fit_id/11132/Year/2004/Make/GMC/Model/Canyon?gclid=CJGg7sPHhsMCFRRcfgod5gsA9g
you can find it at almost any auto parts store just to give u an idea. Right side kicker panel. Good luck.

WAY TO GO !!! another "great idea" from vehicle manufactures

If you have separate bulbs for the low and high beams(4 light system), if you pull the turn signal and hold it, all 4 lights will stay on until you release the turn signal. You need to replace the bright bulb on the right side and the low bulb on the left side. If your headlights only have one bulb on each side, then you will have to replace both of them to get everything to work.

Power for the headlights on the Left side (High and low beam.) comes from the same fuse... The ORANGE wire and the ORANGE/BLACK are the same, they connect in the harness. If you only lack the 12v to make the light work connect them at the headlight assembly.

If your low beam also lacks ground the Left low beam ground is shared with the right low beam ground... Run a wire from left low beam DARK BLUE to right low beam DARK BLUE/WHITE.

If its not working now then your cursed, seek a witch doctor.

If you have a service vehicle soon light (not service engine soon) this usually indicates a problem with the foreward lamp system.Your problem seems confusing, but check your high beam lamp operation. These cars are NOTORIOUS for corroded harnesses to the headlights. The problem is usually buried behind the washer bottle or across the radiator area. If you are lucky, it may be a burned out high beam bulb. If the blue symbol for brights stays on and there is no click when pulling on high beam lever, you will need a new turn signal switch.

most of those issues i have dealt with are the connector on the turn signal switch or the switch itself

plug may not be completely installed? wire the low and high to each other.