Fault Family
System: Powertrain (P-Codes)
4 SAE Codes
AC Compressor Speed Relay Control
Diagnostic & Technical Explanation
Code P0EC5 sets when the control module commands the electric A/C compressor's speed/power relay to a state and does not see the matching current draw or compressor RPM feedback within the diagnostic window. The most common physical causes are welded or pitted relay contacts that no longer switch cleanly, a corroded relay socket or connector, and a relay coil that has failed open. Because the relay gates the compressor's HV feed rather than a signal circuit, a relay that fails closed can leave the compressor running when it should be off — a distinct failure mode from the sensor and control-module faults covered elsewhere in this family group.
These 4 diagnostic trouble codes share one
detection mechanism and one repair path, which is why MechanicDB groups them into a single
authored fault family rather than repeating the same explanation 4 times.
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)