Diagnostic article Generic OBD-II
P2516: Low-side refrigerant pressure must respond after compressor start
Understand the start-to-end pressure change used by this GM low-side refrigerant sensor performance monitor.
Read before applying this article
Documented application
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.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P2516 identifies a low-side refrigerant pressure sensor that appears stuck in the cited GM hybrid controller. It is a response test: the controller compares pressure at the start of the diagnostic with pressure at the end, rather than merely checking whether the input lies inside its voltage limits.
The expected change has a time window
The listed failure is a start-minus-end pressure difference below 4 kPa after 180 seconds. Compressor off-time must exceed 3,600 seconds, and the compressor running flag must be true within the specified early running interval, below 185 seconds. A pressure snapshot taken after an arbitrary period of operation is therefore not equivalent to this monitored event.
The engine-coolant-minus-outside-air-temperature difference must also be below 15°C. Valid temperature information matters because the controller uses the thermal starting conditions to qualify the comparison. P2517 and P2518 pressure-circuit faults inhibit this performance test, as do listed temperature and processor faults.
What the result does and does not show
A nearly unchanged pressure signal under these conditions supports the controller's stuck-sensor finding. It does not independently identify refrigerant charge, prove compressor failure or specify an external gauge test. Those questions require the vehicle's refrigerant-system procedure.
A useful verification record includes compressor state, elapsed running time, the pressure trend and whether the diagnostic actually completed. This calibration uses a one-trip Type A result, so a single qualified event can matter. Refrigerant work and any hybrid compressor electrical testing belong with appropriately equipped personnel.
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.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
A/C Refrigerant Pressure Sensor B Circuit Range/Performance
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT