1997 gmc 3500 hd ...new headlight switch , new dtr relay, all grounds good, daylight running lights work ,marker lamps work...headlights will not come one but marker lights do..highbeams do not work either

fix head lamps first, they work key on, or key off, simple
so a lose fuse? for HL
got DLR lamps in USA truck> daylight running lamps.
HD tailer hitch option?
head lamps Low and high dead or both and flash highs fails ???????
park lamps work? front and rear?
4wd out means 4wd does not work or only the silly 4wd lamp.
???????????????
yes park lamps are related to interior , back ground lamps (dimmed too) and lots of relays and BCM for all that.
check for more lamps dead inside and outside. good and bad
the truck came in 3 trim levels and lots of options added for all this.
even auto dim etc.

is it so hard to tell your country or where it was first sold???

got DRL?
daylight running lamps. Yes/NO?
you known it but did not say.or bought a dead car like this>?

is this USA CAR or canada car , not told up north is DRL land.
not here. (rare and ended 2010 laws make it not mandatory USA)_
So we defeat them here.
just buy and old car lie this failing
or just now failed,??? so blinder and head lamps fail
well fuses are first, check the fuses, all of them.
GOT THIS.
GAUGE FUSE AND DRL FUSE MUST BE GOOD FOR DRL MODULE TO WORK


AND THIS
™ Lighting Control Module by ACDelco®. Designed utilizing the latest technology, this product by ACDelco features premium quality and will perform better than... more details on - https://www.carid.com/1995-gmc-jimmy-light-relays-sensors-control-modules/

Park, Tail and Marker Lamps
The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The PARK LPS 30 A fuse in the engine wiring harness junction block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the FR PRK 10 A fuse, RR PRK 10 A fuse, LR PRK 10 A fuse, and the TRL PRK 15 A fuse, and to their respective park and marker lamps. The front park and marker lamps are grounded at G100. The rear park and marker lamps are grounded at G401. The license lamps are grounded at G401. If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the park, tail and marker lamps approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the park, tail and marker lamps will remain on until turned off or the battery runs dead.
The CTSY LMP 15 A fuse in the engine wiring harness junction block supplies battery positive voltage to both the inadvertent power relay switch contacts and the inadvertent power relay coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the driver presses the cargo lamp switch, the BCM energizes the inadvertent power relay. Current flow is from the inadvertent power relay to the cargo lamps. The cargo lamps are grounded at G203.

What about them ? What front lights ? Headlamps , park lamps, marker lamps ? They don't work ?

Exterior Lamps
The exterior lighting system consist of the following lamps:
• The Headlamps
• The Daytime Running Lamps (DRL)
• The Clearance Lamps (Y92 roof rack only)
• The Cornering Lamps
• The Front Fog Lamps
• The Rear Fog Lamps (Export)
• The Park, Tail and Marker Lamps
• The Turn Signal Lamps
• The Stop Lamps
• The Backup Lamps

Park, Tail, Marker, License, and Clearance Lamps
The park, tail, marker, license, and clearance (Y92 only) lamps are turned on when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The I/P BATT fuse in the engine wiring harness junction block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on, the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the individual park lamp circuit fuses and to their respective park, tail, marker, and license lamps. The front park and marker lamps are grounded at G107 and G103. The tail lamps are grounded at G401 and G402. The license lamps are grounded at G401. When equipped with the Y92 roof rack option, the clearance lamps are grounded at G302. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, the park, tail, marker, license, and clearance lamps will remain on until turned off or the battery runs dead.
The T PARK fuse in the rear fuse-relay block supplies battery positive voltage to a separate park lamp circuit connected to the trailer wiring harness.

Do your headlamps work ?
Park/Marker/License/Tail Lamps
Voltage is applied to the turn/headlamp switch at all times. When the turn/headlamp switch is in the PARK or the HEAD position, voltage is applied to the following components:
?€¢
The park lamps

?€¢
The marker lamps

?€¢
The tail lamps

?€¢
The license lamp

The front marker lamps are grounded through the turn filament of the respective front park/turn lamp. The front marker lamps light as a result.
The automatic lamp control function turns on the park lamps and the headlamps. This action occurs when the ambient light sensor determines that the exterior lamps should be turned ON based on the amount of available light. When the BCM grounds the park lamp relay, voltage is supplied directly to the park lamps, bypassing the turn/headlamp switch assembly. When this action occurs, the following conditions exist:
?€¢
The automatic lamp control relay is grounded.

?€¢
The headlamps turn ON. Refer to Headlights/Daytime Running Lights (DRL) Circuit Description .

The lamps turn OFF when the BCM does not ground the park lamp relay or the automatic lamp control relay. This action is caused by the following conditions:
?€¢
The available light reaches a predetermined level.

?€¢
The ignition switch is turned to the OFF position

Check fuse's #19 ,# 6 #4 check grounds 105 & 107
G107 In the left rear of the engine block next to the knock sensor. G105 In the thermostat housing
The park, tail, marker and license lamps are turned on when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The PK LPS fuse in the IP fuse block supplies battery positive voltage to the park lamp relay and the headlamp switch. The body control module (BCM) provides a ground, or control circuit, to the park lamp relay coil circuit during ALC operation. When the park lamps are turned on during ALC, the BCM energizes the park lamp relay. The park lamps can also be supplied battery positive voltage directly from the headlamp switch. Current flow is to the park, tail, marker and license lamps. The front park and marker lamps are grounded at G100 and G101. The rear park, tail, marker and license lamps are grounded at G400 and G401. If the headlight switch is left in the ON position, the park, tail and marker lamps will remain on until turned off or the battery runs dead.
Check the headlamp switch !

Not sure I follow you.
Since 2000 most GM models use the dimmer switch and headlight switch to ground the lights instead of providing power.
The headlights get power from fuses for left and right, control is on the ground circuit side. So the ground wires go thru the dimmer then the headlight switch to complete the circuit.
The body control module grounds the headlight relay.

they are dual filament bulbs so the tail light filament might have blown and not the stop light , replace the bulb to check

both headlights?
many cars have 2 fuse one for left and one for right.
the operators guide shows fuses. fues 45 and 46 (HL left/right)
USA answer, if in Canada, with DRL light, do say so now....
(daylight running light option)
this car has headlight relay,
the HL switch ground the HL relay coil, the coil energizes and
12v power hits both head light fuses. and then lamps.
the lamps are grounded and glow.
the schematic is on alldata.com
easy tests. with any voltmeter.

Do you have tail ligts and side marker lights with drls on? if so you will have only dim headlights. Check fuses, I think the headlights are fused seperately.