What fuse or relay controls the tail lights and dash lights on a 2006 sterling dump truck?

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.

have you checked the tow tail light fuse or the tow tail light relay?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

In the instrument panel fuse block is a fuse marked PK LAMPS the fuse directly above is a 10 amp fuse ,this is the one you want to check. There is also a relay involved in making the park lights work and the Body control module .The relay is in the same fuse block as the PK LAMP fuse, marked PK LP . Not to sound like I'm talking down to you but do you know what a relay looks like ? The fuse block is Right side of the I/P, behind the access panel. Open the passenger door , at end of the Dash is a panel ,pull it off ,then you'll see fuse box .On the inside of the panel it tells what each fuse and relay is. I'm going add how the park lights work description.
The PARK LAMPS fuse in the instrument panel (I/P) fuse block applies battery positive voltage to both the coil and switch side of the PARK LAMP relay in the I/P fuse block. When the headlamp switch is placed in either the PARK or HEAD position, ground is applied from G202 to the headlamp switch. The headlamp switch then applies the ground through the park lamp switch ON signal circuit to the body control module (BCM). The BCM then applies a ground to the PARK LAMP relay enable circuit. This energizes the PARK LAMP relay, applying battery positive voltage to all the park, tail, marker and license lamps. The park, tail, marker and license lamps are also turned ON when the headlamps are commanded ON by the BCM for low light operation. Good luck !

tail lamp are really parking lamps after all the fronts glow and the rear, and the sidemarkers and the dash lamps all glow, with the
Headlight switch 1 click, do that all fail, up to 20 lamps.
this is key fact, and makes diagnosis far more easy.
turn dash cabin dimmer on high. too.
the fuse box i most cars they will be marked, TAIL or PARK
did you even look?
ok the schematic is on my screen,(alldata.com)
fuse j4----j5 location then to PK relay both in the IP fuse box,
IP= instrument panel.
THE BCM controls this relay
the BCM sees you turn the digital swtch to park and then closes the relay, it is that simple.

the fuse is marked PK lamps, (as in parking)

Check the fuse. A bad bulb can cause a fuse to blow.

Power is supplied to the instrument illumination by the "TAIL/ILLUM LIGHT" fuse, Fuse #4 (15 Amp) located in the dash fuse block under the left side of the dash. This fuse provides power for both the primary and secondary sides of the TAIL LIGHT relay. The Combination (Headlamp) switch provides a ground path for the primary circuit of the TAIL LIGHT relay. When the primary circuit is completed by the Combination switch, the secondary contacts close and provide power to the tail lamps as well as to all of the instrument illumination bulbs. The ground for the instrument illumination bulbs is a variable-resistance circuit which is controlled by the illumination controller. The final ground for both the combination switch and the illumination controller is Ground G302, located under the center console.

Before you get started, please review this article: Where's The Fuse?

Keeping the information in the article above in mind, the fuse that supplies power to the marker lights is located in the engine compartment fuse block It is fuse# 60. it is a 10 Amp fuse. This fuse supplies power to the Tail Lamp Relay which is located in relay box #1. This relay is controlled by the Auto Light Control Unit, which in turn, is controlled by the main lighting switch.
The Auto Light Control Unit gets its power from fuse #30 (10 Amp) which is located in the Instrument panel fuse block under the left side of the dash.

The tail and marker lights and Instrument lights are on the same circuit so both will go out if the fuse for this circuit blows. If fuse continues to fail, check the tail light or marker globes, including the globes for the number plate, for a globe that may have an internal short causing the fault and replace as necessary. As you have already checked the wiring near the light fittings for any chafed wires that could be shorting to the body causing the fault, then a closer inspection of the wires inside all the light assemblies for any shorts may be needed.

It could also be that the instrument dimmer control has failed and is causing the fault. The electronic bits inside the dimmer control for these lights sometimes go faulty. Try disconnecting the connecting plug on the rear of the dimmer control and checking if fuse still blows. If fuse continues to fail, then the fault in the tail and marker lights circuit.

Remove all the tail, number plate and running light globes from the light assemblies and leave the instrument dimmer control disconnected and check if fuse still blows.

Disconnect the plug near each of the light assemblies to see if any of the individual assemblies is causing the fault. With all light assemblies disconnected and fuse continues to fail, then the fault must be in the main wiring loom some where.

If you have a Multimeter, it could be used to determine which light assembly has a fault between the lamp supply and earth connection.

I had the same issues. Dash dead, tail lights dead. Fuses were fine, Dimmer relay was fine...So I got to the Tail Light Relay.

Removed the glove box, one screw on the right. Reach up (above the space where the glove box 'area' would be and there are 3 or 4 relays all sitting on top of a junction box. All of them were loose. I pushed them in...and voila! I was getting scared after the obvious.