My DRL flashes on the instrument panel and then goes out. No low or high beams work.

Hello. It seems your Chevrolet has either faulty headlamp relay(s) or its headlamps are connected in series; if one don't light, neither will the other one. I can't explain why the 'CHECK ENGINE' light was still on while your truck's engine was off and key was out of ignition switch. Good luck and keep me informed; if you want to.

Low Beam System Operation
The headlamps may be turned on two different ways. First, when the end of the of the turn signal/headlamp switch lever is turned to the second detent position, the headlamps will illuminate. A ground signal is provided to the DRL control module. The module then provides a ground path to the coils of the HLP relay. Since the head relay is provided with battery voltage to both the contacts and the coil, the coil becomes energized and closes the contacts providing voltage to the DIM relay. With voltage and ground provided, the low beam lamps light. Second, with the switch in the OFF position, for automatic lamp control (ALC). During ALC the headlamps will be in one of the following modes of operation:
• Daytime running lamp (DRL) operation in daylight conditions, refer to DRL below for the operation of the circuit.
• Low beam headlamp operation in low light conditions. When the ambient light sensor senses a low light condition for approximately 15 seconds, it will cancel DRL operation and turn on the headlamps at 100 percent intensity. A path to ground is provided to the coil of the HLP relay. With a direct path to ground provided to the headlamps though the DRL control module, the headlamps will light at 100 percent intensity.
High Beam System Operation
The high-beam headlamp operation is controlled using the turn signal/headlamp switch lever on the steering column. In order to change headlamp operation from low-beam to high-beam, push the switch lever toward the instrument panel (until the detent is felt) and release. With the switch lever in the high beam position, ground is provided to the DRL control module through the turn signal/headlamp switch and splice pack 200 to G200. The DRL control module provides a ground to the coil of the dimmer relay. Since voltage is being applied to the dimmer relay coil, it becomes energized. Voltage is then applied through the closed contacts of the dimmer relay and the to the high beam lamps in the headlamps. Since ground is provided to the headlamps through the closed contacts of the energized DIM relay, the high beam lamps light. The high-beam indicator (blue) in the instrument cluster will light during high-beam headlamp operation. In order to change headlamp operation back to low-beam operation, pull the turn signal switch lever toward the driver (until the detent is felt) and release.Your best bet , take it to a qualified repair shop.

Headlamps
The headlamps are operated when the driver places the headlamp switch in the HEADLAMP position. The LT HDLP and RT HDLP fuse in the IP fuse block, supply battery positive voltage to both the left and right headlamps. The low beam and high beam circuits continue to the headlamp switch. Depending on the position of the dimmer switch, either the low or high beam circuit will now have a path to ground. Ground is provided at G204. The low beam and high beam circuits also provide the body control module (BCM) with both low and high beam inputs. The headlamp switch includes the dimmer and the flash-to-pass switch.
If the headlight switch is left in the HEADLAMP position, the headlights will remain on until turned off or the battery runs dead.
Daytime Running Lamps (DRL)
Any function that turns on the headlights will cancel the daytime running lamps operation. The LT HDLP fuse in the IP fuse block supplies battery positive voltage to the daytime running lamp (DRL) relay coil circuit. The DRL relay switch contacts are connected to the low beam circuit. When the headlamp switch is placed in the OFF position, the BCM will turn on the daytime running lamps. The BCM energizes the DRL relay, closing the switch contacts and grounding the low beam circuit at G204. The DRL illuminate the low beam headlights at a reduced intensity. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position and the parking brake is released. When these conditions have been met the DRL will illuminate.
DRL operation in Manual Transmission equipped vehicles will occur when the ignition switch is in the RUN position, and the parking brake is released.

Probably the dimmer switch . But without testing that would be just a guess . Turnning the headlamps on Any function that turns on the headlights will cancel the daytime running lamps operation..
No ,don't think the DRL relay has anything to do with it .

View wiring diagrams an testing the electrical circuits at the dimmer switch would be the proper way to diagnose .

There's headlight relays for both low and high beam (if I recall correctly) and a main relay (on the junction box near the battery). I'd guess initially that a relay is faulty.

If its the daytime running lights (DRLs) that are flashing the high beam on and off, they are controlled by a combined oscillator and relay box (looks like a large relay can). This box provides about 9v to the HB lights to provide the DRL function. You can disconnect the DRL box and see if the problem goes away.

HB and LB are separate from the DRL circuits. If the HB or LB are flashing (ie at night), I'd suspect the main relay.

SD

I have the same problem and I've tried two fixes so far and neither has worked.
- I replaced the daytime running light module and that didn't work
- I replaced the trun signal/hazard/light switch and that didn's work

I've had one comment that it could be a ground issue.
hope this saves you spending money on "fixes" that don't solve the problem

What relay's ?
The instrument cluster controls the headlamp systems that include daytime running lamps (DRL). The system allows the headlamps to operate at a reduced intensity when all of the following conditions apply:
• The engine is running.
• The transaxle is not in the PARK position.
• The normal headlamps are not on.
The instrument cluster turns the DRL system on by grounding CKT 592, thereby energizing the DRL relay. This action allows a reduced voltage of 6 volts to flow across the headlamps. If the vehicle has the optional fog lamps, the fog lamp relay will also be energized. The park lamps will turn on and the fog lamps will operate normally. When the headlamp switch is turned to the ON position, the instrument cluster allows normal headlamp operation.
The instrument cluster also has an input from the park brake. If the park brake is in the ON position, the DRL will remain disabled until the park brake is placed in the OFF position. On vehicles with an automatic transaxle, the instrument cluster will disable the DRL until the transaxle has been taken out of the PARK position.

Headlamps Inoperative - High Beams
Step
Action
Value(s)
Yes
No
1
Did you perform the Daytime Running Lamps (DRL) System Check?
--
YES - Go to Step 2
NO - Go to Daytime Running Lights (DRL) System Check
2
Disconnect the turn/hazard headlamp switch connector C1.
Connect the fused jumper between terminal B of the turn/hazard headlamp switch assembly harness connector C1 and ground.
Do the high beam headlamps operate?
--
YES - Go to Step 3
NO - Go to Step 4
3
Replace the turn/hazard headlamp switch assembly.
YES - Did you complete the repair?
--
NO - Go to Daytime Running Lights (DRL) System Check
--
4
Repair the open in CKT 1200 between the turn/hazard headlamp switch assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
Go to Daytime Running Lights (DRL) System Check
--

Reqired replace of DRL

Headlight Switch itself If Not then this Very Well May be in your Multifunction Switch

Daytime Running Lamps
The daytime running lamp (DRL) system is designed to turn the high beam headlamps on, with a reduced light output, and without illuminating the high beam indicator lamp in the instrument panel. You have a DRL Module.
The multifunction switch is the stalk on your column.

This is 96 F150 circuit. Don't have 94.


Symptom Chart, Headlamps HEADLAMPS Condition Possible Source Action

• Headlamps Inoperative

• Circuitry open/shorted.
• Damaged headlamp switch.
• Blown fuse.

• GO to Pinpoint Test A .

• Headlamps On Continuously

• Circuitry open/shorted.
• Damaged headlamp switch.

• GO to Pinpoint Test B .

• High Beams or Low Beams Inoperative

• Circuitry open/shorted.
• Damaged multi-function switch.

• GO to Pinpoint Test C .

• One High Beam or One Low Beam Headlamp Inoperative

• Circuitry open/shorted.
• Damaged connector.
• Headlamp bulb damaged.

• GO to Pinpoint Test D .

• Flash-to-Pass Inoperative

• Blown fuse.
• Circuitry open/shorted.
• Damaged multi-function switch.

• GO to Pinpoint Test E .

Notes CIRCUIT OPERATION - CANADA
On Canadian vehicles, the low-beam headlamps operate when the ignition switch is in the RUN position and the headlamp switch is OFF.

When the ignition switch is in the START or RUN position, circuit A1 from fuse 15 in the Power Distribution Center (PDC) connects to circuit A21. Circuit A21 powers circuit F18 through fuse 19 in the fuse block. Circuit F18 feeds the Daytime Running Module (DRL) module.

Circuit L20 from the headlamp switch connects to DRL module. Circuit L20 is HOT at all times.

The DRL module receives the vehicle speed sensor input from circuit G7. Circuit G34 from the DRL module provides power for the high beam indicator lamp in the instrument cluster.

Circuit L4 powers the low beams of the headlamps. When the headlamp switch is OFF, the DRL module powers the low beams on circuit L4. When the headlamps are ON, the multi-function switch powers the low beams on circuit L4.

Circuit L3 feeds the high beams of the headlamps. When the operator flashes the headlamps with the stalk of the multi-function switch, the DRL module senses voltage on circuit L3. When it senses voltage on circuit L3, the DRL module stops supplying power to the low beams on circuit L4.

Circuit Z1 provides ground for the DRL module.