Code B131, Engine Oil Pressure Switch Circuit Problem: Notes

Fig 1: Code B131 Flowchart, Engine Oil Pressure Switch Ckt Problem

Fig 2: Code B131 Flowchart, Engine Oil Pressure Switch Ckt Problem

Fig 3: Code B131 Schematic, Engine Oil Pressure Switch Ckt Problem

If the vehicle you are working on is equipped with gauges, you are on the wrong chart. See Code B131 AND/OR B132, ENGINE OIL PRESSURE SENSOR CIRCUIT PROBLEM.

The oil pressure indicator (without gauges) uses a switch to control the signal voltage to the BCM. The BCM supplies a voltage on circuit 313 to the switch. When the engine is running, oil pressure holds the switch contacts open, therefore, the BCM will see a high signal voltage. As oil pressure drops, the switch contacts close and the signal voltage is pulled low through the sensor ground (switch is case grounded).

Code B131 will set during "Display-on-Entry", if the signal voltage is high (open circuit). In other words, when the engine is not running and oil pressure is low, the switch contacts should close and pull the signal voltage low. A shorted to ground circuit will show up as low oil pressure all the time.

1. BCM input BI26 displays oil pressure at "HIGH" or "LOW", depending on the voltage state at the BCM.
2. Checks to see if the "HIGH" reading is due to the circuit or the switch. With the engine off, if the display changes from "HIGH" to "LOW", when the connector is jumped to ground, the BCM and wiring are okay.
3. Checks to see if the "HIGH" reading is due to the BCM or the circuit. If the display changes from "HIGH" to "LOW", when BCM terminal cavity is backprobed to ground, the BCM is okay.