For 1990-2009 cars

### CHECK OIL LEVEL Indicator (Buick)

The oil level sensing system consists of the following components:

• | An oil level sensor

• | The powertrain control module (PCM)

The oil level is indicated in the following manner:

1. The oil level sensor provides the oil level signal to the PCM on CKT 1174 (BRN).
2. The PCM processes the signal.
3. If the PCM determines that a low oil level condition exists, the PCM grounds CKT 1173 (BRN/WHT).
4. The CHECK OIL LEVEL indicator illuminates.

### CRUISE Indicator

The cruise indicator illuminates in the following manner:

1. The instrument cluster receives cruise data from the powertrain control module (PCM) over the universal asynchronous receiving/transmitting (UART) serial data line.
2. The instrument cluster converts the serial data.
3. The PCM commands the instrument cluster to illuminate the CRUISE indicator.

### LOW COOLANT Indicator (Buick)

The low coolant indicator illuminates in the following manner:

1. The engine coolant level sensor provides a signal to the instrument cluster on CKT 68 (YEL/BLK).
2. If the engine coolant level is low, the sensor grounds CKT 68.
3. The LOW COOLANT indicator illuminates.

### LOW WASHER FLUID Indicator (Buick)

The low washer fluid level indicator illuminates in the following manner:

1. The windshield washer solvent level switch provides a signal to the instrument cluster on CKT 99 (BLK/WHT).
2. If the washer fluid is low, the sensor grounds CKT 99.
3. The LOW WASHER FLUID indicator illuminates.

### OIL Indicator

The oil indicator illuminates in the following manner:

1. The engine oil pressure switch provides a signal to the instrument cluster on CKT 231 (TAN/BLK).
2. If the oil pressure is low (below 2 psi) the switch is closed, grounding CKT 231.
3. The OIL indicator illuminates.

### VOLTS Indicator

The volts indicator illuminates in the following manner:

1. The instrument cluster receives charging data from the powertrain control module (PCM) over the universal asynchronous receiving/transmitting (UART) serial data line.
2. The instrument cluster converts the serial data.
3. The PCM commands the instrument cluster to illuminate the VOLTS indicator.