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Headlamps 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

Dipped Beam Headlamp Supply Voltage

1

1

3

--

Main Beam Headlamp Supply Voltage

2

2

4

--

Headlamp Dipped Beam Relay Control

3

1

1

--

Headlamp Main Beam Relay Control

4

2

2

--

Headlamp Switch Headlamps On Signal

--

1

1

--

Park Lamp Switch On Signal

--

1

1

--

Dipped Beam Headlamp Ground

--

1

--

--

Main Beam Headlamp Ground

--

2

--

--

Indicator/Multifunction Switch Ground

--

1, 2

--

--

1. Dipped Beam Headlamp(s) Inoperative

2. Main Beam Headlamp(s) Inoperative

3. Dipped Beam Headlamp(s) Always ON

4. Main Beam Headlamp(s) Always ON

Circuit/System Description

Dipped beam

The vehicle headlamps are controlled by the I/P fuse block based on inputs from the indicator/multi-function switch. The headlamp switch has three positions: Off, Parking light, and Low beam. The Park position of the indicator/multi-function switch will only illuminate the vehicle parking lamps. The Headlamp position of the indicator/multi-function switch will illuminate both the parking lamps, as well has the headlamps. With the indicator/multi-function switch in the Headlamp position, the indicator/multi-function switch headlamps on signal circuit is grounded, prompting the I/P fuse block to turn on the headlamps.

Main Beam

The headlamp main beams are controlled through the flash to pass switch and the headlamp dimmer switch, both located in the indicator/multifunction switch. The flash to pass switch is a momentary type switch, designed to illuminate the main beams as long as the switch is held. With the switch closed, the main beam relay control circuit is grounded, this energises the main beam relay, closing the switch side contacts of the main beam relay, applying battery voltage to the main beam fuses. The headlamp dimmer switch allows the operator to select between full time high or dipped beam operation. Unlike the flash to pass switch, it is not a momentary switch.

Circuit/System Verification
  1. Ignition ON, observe the headlamps while cycling the headlamp switch between the ON and OFF positions. The headlamps should cycle between ON and OFF.
    2. ⇒If the headlamps do not cycle between ON and OFF, refer to Headlamp Switch Malfunction.
  2. With the dipped beams ON, observe the headlamp main beams while pulling and releasing the indicator/multifunction switch. The headlamp main beams should cycle between ON and OFF.
    3. ⇒If the headlamp main beams do not cycle between ON and, refer to Indicator/Multifunction Switch Malfunction.
  3. With the dipped beams ON, observe the headlamp main beams scan tool Main beam Select Switch parameter while switching the Indicator/Multifunction Switch between the dipped and main beam positions. The headlamp main beams should cycle between ON and OFF.
    4. ⇒If the headlamp main beams do not cycle between ON and OFF, refer to Indicator/Multifunction Switch Malfunction.

Circuit/System Testing

Headlamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the S78 Indicator/Multifunction Switch.
  2. Verify that a test lamp illuminates between the ground circuit terminal 7 (X1) and B+.
    3. ⇒If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Verify that a test lamp illuminates between the ground circuit terminal 4 (X2) and B+.
    4. ⇒If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for B+ between the signal circuit terminals listed below and ground:
    5. • Headlamp switch dipped beams ON signal terminal 5 (X1)
    • Park lamp switch ON signal terminal 1 (X2)
    ⇒If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the I/P Fuse Block
  5. Install a 3 A fused jumper wire between the park lamp ON signal circuit terminal 1 (X2) and ground. Verify that a park lamp illuminates.
    6. ⇒If the park lamp does not illuminate, test the signal circuit for a short circuit to voltage or an open/high resistance. If the circuit tests normal, replace the I/P Fuse Block.
    ⇒If the park lamp does illuminate, test the signal circuit for a short circuit to ground. If the circuit tests normal, replace the I/P Fuse Block.
  6. Install a 3 A fused jumper wire between the dipped beams ON signal circuit terminal 5 (X1) and ground. Verify that headlamp dipped beams illuminate.
    7. ⇒If the headlamp dipped beams do not illuminate, test the signal circuit for a short circuit to voltage or an open/high resistance. If the circuit tests normal, replace the I/P Fuse Block.
    ⇒If the headlamp dipped beams do illuminate, test the signal circuit for a short circuit to ground. If the circuit tests normal, replace the I/P Fuse Block.
  7. If all circuits test normal, replace the S78 Indicator/Multi-Function Switch.

Dipped beam Headlamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate head lamp.
  2. Test for less than 5.0 Ω between the appropriate head lamp ground circuit wiring harness plug listed below and ground.
    3. • E13L Headlamp Assembly - Left ground circuit harness connector terminal 1
    • E13R Headlamp Assembly - Right ground circuit harness connector terminal 1
    ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the appropriate head lamp control circuit harness connector listed below and ground.
    4. • E13L Headlamp Assembly - Left signal circuit harness connector terminal 2
    • E13R Headlamp Assembly - Right signal circuit harness connector terminal 2
  4. Turn the headlamps ON and OFF. The test lamp should turn ON and OFF when changing between ON and OFF.
    5. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the I/P Fuse Block.
    ⇒If the test lamp is always OFF, test the Signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the I/P Fuse Block.
  5. If all the circuits test normal, replace the appropriate headlamp.

Main beam Headlamp Malfunction

  1. Ignition OFF, disconnect the appropriate harness connector at headlamp lamp listed below:
    2. • E13L Headlamp Assembly - Left
    • E13R Headlamp Assembly - Right
  2. Disconnect the negative terminal of the C1 Battery.
  3. Test for less than 5 Ω between the appropriate headlamp ground circuit harness connector terminal 1 and ground.
    4. ⇒If greater than the specified value, test the ground circuit for an open/high resistance.
  4. Reconnect the negative terminal to the C1 Battery.
  5. Remove the F12UB Main beam fuse. Verify that the headlamp does not illuminate.
    6. ⇒If the headlamp does illuminate, test the signal circuit for a short to voltage.
  6. Install a 10 A fused jumper wire between appropriate fuse output contact and B+ Verify that the appropriate main beam illuminates.
    7. ⇒If the main beam lamp does not illuminate, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate bulb.
  7. Disconnect the X1 wiring harness plug at the X50A Fuse Block - Under bonnet.
  8. Connect a test lamp between the signal circuit terminal 13 (X2) and B+.
  9. Ignition ON, switch the main beam lamps ON and OFF by using the S78 Indicator/Multifunction Switch. The test lamp should go ON and OFF.
    10. ⇒If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit tests normal, replace the S78 Indicator/Multi-Function Switch.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the S78 Indicator/Multi-Function Switch.
  10. If all circuits test normal, replace the X50A Fuse Block - Underhood.

Component Testing

Static Test - Headlamp Switch

  1. Ignition OFF, disconnect the harness connector at the S78 Indicator/Multifunction Switch.
  2. Test for infinite resistance between the signal terminal 1 (X2) and the ground terminal 7 (X1), 4 (X2) with the switch in the OFF position.
    3. ⇒If not the specified value, replace the S78 Indicator/Multifunction Switch.
  3. Test for infinite resistance between the signal terminal 5 (X1) and the ground terminal 7 (X1), 4 (X2) with the switch in the OFF position.
    4. ⇒If not the specified value, replace the S78 Indicator/Multifunction Switch.
  4. Test for infinite resistance between the signal terminal 4 (X1) and the ground terminal 7 (X1) with the headlamp dimmer switch in the dipped beam position.
  5. Test for less than 2 Ω between the signal terminal 1 (X2) and the ground terminal 4 (X2) with the switch in the Park position.
    6. ⇒If not the specified value, replace the S78 Indicator/Multifunction Switch.
  6. Test for less than 2 Ω between the signal terminal 5 (X1) and the ground terminal 4 (X2) with the switch in the Dipped beam position.
    7. ⇒If not the specified value, replace the S78 Indicator/Multifunction Switch.
  7. Test for less than 2 Ω between the signal terminal 4 (X1) and the ground terminal 7 (X1) with the headlamp dimmer switch in the main beam position.
    8. ⇒If not the specified value, replace the S78 Indicator/Multifunction Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Indicator Switch Replacement
    •  Headlamp Bulb Replacement
    •  Relay Replacement : Within an Electrical Center → Attached to Wire Harness
    •  Headlamp Replacement
   


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