Code Definition

P1189 — Engine Oil Pressure Switch circuit

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: GM

About P1189

P1189 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1189 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1189 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

Unlike the oil pressure sensor, which reports a variable voltage proportional to pressure, the engine oil pressure switch is a simple two state device that changes state once gallery pressure crosses a fixed threshold, commonly in the region of 30 kPa to 55 kPa. The Engine Control Module (ECM) applies a voltage to the switch circuit and monitors whether that circuit is pulled to ground or left open, and it uses the resulting on or off state to confirm that oil pressure has been established after start up and, on some applications, to enable functions such as cylinder deactivation or a fuel pum...

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