P2518: High refrigerant sensor voltage has its own sample and trip logic

The cited GM P2518 monitor identifies refrigerant pressure sensor B above its accepted electrical range. For this low-side sensor, the boundary is greater than 98% of the reference voltage, shown as 4.9 V. The figure is not an allowable refrigerant-system pressure or an instruction to release refrigerant.

Understand what “high” describes

The failed quantity is sensor voltage. A high pressure value calculated from that voltage is not independent confirmation of excessive mechanical pressure. The source does not identify whether the sensing element, supply, connection or signal circuit produced the invalid reading.

This monitor has different recognition logic from its low-input partner. P2518 needs 40 failing samples out of 50 at 100-millisecond intervals and is classified as one-trip Type A. P2517 uses 16 of 20 samples and a two-trip Type B strategy. A shared sensor does not mean the two faults have identical event or warning histories.

Verify the input before assessing response

System voltage must exceed 10.2 V. P2518 also prevents the P2516 stuck-sensor performance check from running. As a result, restoring a believable voltage and completing a pressure-response diagnostic are separate verification steps.

Capture input voltage, controller supply context and compressor state before clearing the event. A subsequent normal pressure display alone cannot prove that the sampled electrical fault has been resolved. The source is a monitor summary, not a charging, venting or hybrid compressor test procedure; any work involving refrigerant or high-voltage equipment requires the applicable professional service method.

Source and applicability

GM 2015 15OBDG01 Hybrid Diagnostics, HCP2 (VICM) low-side refrigerant pressure monitor on physical page 572. Per-model applicability and sensor location are not established here; electrical limits are specific to the documented calibration.

General Motors source, physical page 572