GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2008 🢒 Isuzu MD F-Series 🢒 Body Systems 🢒 Lighting 🢒 Daytime Running Lamps Malfunction

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

DRL Indicator Relay B+

1

1

--

--

DRL Indicator Relay Control

2, 5

1

--

--

DRL OFF Relay Ignition

2, 4

2, 4

1, 3

--

DRL OFF Relay Control

7

2, 4, 7

--

--

Ground -- DRL OFF Relay

--

2, 4

--

--

Lighting Relay B+

1

2

--

--

Lighting Relay Control

5

6

--

--

DRL Control

1, 3

2, 4

--

--

1. DRL indicator always ON

2. DRL indicator inoperative

3. DRL always ON

4. DRL inoperative

5. Headlamps always ON

6. Headlamps inoperative

7. Brake warning indicator malfunction

Circuit/System Description

The daytime running lamps (DRL) are active when the headlamp switch is OFF and the ignition is in the ON position. When the ignition is ON, ignition voltage is applied to the coil side of the DRL OFF relay energizing the relay. Ground from G400 is then applied through the DRL control circuit, the switch side of the DRL ON relay, the DRL resistor, and the switch side of the LIGHTING relay illuminating the headlamps at a low intensity. Ground from G400 is also applied through the DRL indicator diode and the switch side of the DRL indicator relay illuminating the DRL indicator in the instrument panel cluster (IPC). When the headlamps are turned ON, ground from G400 is applied through the headlamps ON switch signal circuit to the coil side of the LIGHTING relay and the DRL indicator relay energizing the relays. With the relays energized, the low beam headlamps are turned ON and the DRL indicator is turned OFF. The DRL will also be disabled when the park brake is in the ON position.

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, disable the park brake. Verify that the park brake indicator is OFF.
    2. ⇒If the park brake indicator is illuminated, refer to .
  2. Ignition ON, park brake not engaged, headlights OFF, the DRL should turn ON and the DRL indicator should illuminate.
    3. ⇒If the DRL do not turn ON, refer to DRL Malfunction.
    ⇒If the DRL indicator does not illuminate, refer to DRL Indicator Malfunction.

Circuit/System Testing

DRL Malfunction

  1. Ignition OFF, disconnect the DRL OFF relay.
  2. Test for less than 1.0 ohm between the ground circuit terminal 87 and ground.
    3. ⇒If greater than the specified value, test the ground circuit for an open/high resistance.
  3. Test for infinite resistance between the control circuit terminal 86 and ground.
    4. ⇒If less than the specified range, test the control circuit for a short to ground. If the circuit tests normal, test or replace the park brake relay.
  4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 and ground.
    5. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  5. Ignition OFF, connect the DRL OFF relay and disconnect the DRL ON relay.
  6. Test for infinite resistance between the control circuit terminal 86 and ground.
    7. ⇒If less than the specified value, test the control circuit for a short to ground. If the circuit tests normal, test or replace the DRL engine run diode.
  7. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 and ground.
    8. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  8. Test for less than 5 ohms between the control circuit terminal 87A and ground.
    9. ⇒If greater than the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the DRL OFF relay.
  9. Ignition OFF, connect the DRL ON relay and disconnect DRL resistor.
  10. Test for less than 10 ohms between control circuit terminal B and ground.
    11. ⇒If greater than the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the DRL ON relay.
  11. Disconnect the LIGHTING relay.
  12. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 87A and B+.
    13. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the DRL resistor.
  13. Verify that a test lamp illuminates between the control circuit terminal 30 and ground.
    14. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  14. If all circuits test normal, test or replace the lighting relay.

DRL Indicator Malfunction

  1. Ignition OFF, disconnect the DRL indicator relay and the LIGHTING relay.
  2. Headlamps ON, test for less than 5 ohms between the control circuit terminal 86 and ground.
    3. ⇒If greater than the specified range, test the control circuit for an open/high resistance.
  3. Ignition ON, test for less than 1 volt between the control circuit terminal 87A and ground.
    4. ⇒If greater than the specified range, test the control circuit for a short to voltage.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
    5. ⇒If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Verify that a test lamp illuminates between the control circuit terminal 30 and ground.
    6. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the instrument panel cluster (IPC).
  6. Ignition OFF, connect a 3A fused jumper wire between the control circuit terminal 87A and B+.
  7. Disconnect the DRL ON relay.
  8. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 30 and ground.
    9. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the DRL indicator diode.
  9. If all circuits test normal, test or replace DRL indicator relay.

Component Testing
  1. Ignition OFF, disconnect the appropriate relay.
  2. Test for 70-100 ohms of resistance between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the appropriate relay.
  3. Test for infinite resistance between the following terminals:
    4. • 30 and 85
    • 30 and 86
    • 30 and 87
    • 85 and 87
    ⇒If not the specified value, replace the appropriate relay.
  4. Test for less than 5 ohms of resistance between terminals 30 and 87A.
    5. ⇒If greater than the specified range, replace the appropriate relay.
  5. Install a 15A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 5 ohms of resistance between terminals 30 and 87.
    6. ⇒If greater than the specified range, replace the appropriate relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Daytime Running Lamps (DRL) Resistor Replacement
    •  Relay Replacement
    •  Instrument Cluster Bulb Replacement
    •  Instrument Cluster Replacement