Red
The red LED uses both grounds, pin 4 and 5. This is accomplished by the use of diodes and effects how the red LED will respond to ground issues. For example, if the vehicle wiring to pin 4 has a high resistance problem it will not effect the red LED because it still has a good ground path via diode 2 and pin 5, the signal ground.
As a general rule:
The red LED will dim if:
| • | The battery voltage is low |
| • | The wiring to DLC pin 16 is defective. |
| • | Both ground circuits have resistance issues. |
Green
Each ground LED is connected to battery voltage via pin 16. Therefore, a ground issue on pin 4 will not affect LED 5. A dim individual green LED will indicate a circuit problem with the corresponding circuit.
