Code Definition

P1188 — Engine Oil Pressure Sensor circuit voltage high

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

About P1188

P1188 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 P1188 is stored, the module has detected a signal or supply voltage higher than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

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.

P1188 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

The engine oil pressure sensor is a three wire piezoresistive sensor supplied with a 5V reference and a low reference (sensor ground) by the Engine Control Module (ECM), and it returns a signal voltage proportional to oil gallery pressure. DTC P1188 is set when the ECM sees that signal voltage above the calibrated high threshold, commonly around 4.5V to 4.8V, for longer than the allowed time, which corresponds to an oil pressure reading beyond anything the engine can plausibly produce. In practice a signal that is pinned high almost always means the low reference circuit has gone open or the s...

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