P1189 - FAULT CODE - OBD2

P1189 BUICK, CADILLAC, CHEVROLET, GMC: ENGINE OIL PRESSURE SWITCH FAULT

A vehicle’s engine may have damage without using the right amount of oil. For this reason, manufacturers design some systems to maintain both the correct engine oil pressure and level. Oil flow regulation is controlled by the ECM (Engine Control Module), which relies on the readings provided by the oil pressure switch/sensor. This is connected directly to the oil gauge in the instrument cluster. When a lower than necessary oil pressure is detected, this sensor will cause the gauge to reflect this change.

The Engine Oil Pressure Switch is usually closed. If the oil pressure is above 1-4.5 psi, the switch contacts open. During this process occurs, the ECM sends 12 volts to the oil pressure input circuit. When the oil pressure drops, the 12 volts consequently drop to ground. It is possible to check if the switch circuit is open through this diagnostic. If the engine has been off long enough for the engine temperature to drop to about 10°C, a short should be observed before the engine is started.

The P1189 OBDII fault code is set on GMC, Chevrolet, and other vehicles when an Oil Pressure Switch/Sensor malfunction is detected. Specifically, this situation occurs when oil pressure is detected in the engine, although it has not been started.

• Check Engine light ON.
• Constant blinking of the oil pressure light.

The diagnostic code P1189 OBD2 is set for one of the following reasons:

• The oil pressure switch circuit may have damaged wiring.
• The electrical connections of the Oil Pressure Switch circuit may be faulty.
• The Engine Oil Pressure Switch may be defective.

To solve the DTC P1189 OBDII code, try this:

• Consult the Technical Service Bulletins.
• Inspect the condition of the oil pressure switch cables and connectors. If poor condition due to burns, corrosion, or wear is detected, make the appropriate repairs.
• Check the oil pressure switch/sensor circuit for the right performance, and verify that the oil pressure switch/sensor voltages match those specified by the manufacturer. If you discover an out-of-range voltage, make adjustments.
• If no electrical inconsistencies are found, there may be a faulty switch. Follow the manufacturer's recommendations to check its integrity.