What it means
A receiving module detected implausible data from the A/C compressor control module (typically the inverter for an electric scroll compressor). Speed or torque values fail plausibility checks and are rejected.
How it works
The A/C compressor control module, often an inverter on electric-compressor systems, controls compressor operation and reports speed or torque information. A receiving module sets U046C when those compressor values fail plausibility checks and are rejected.
Common causes
Most likely first.
- Module internal fault or sensor input drift
- Software version mismatch after replacement
- Gateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules and save freeze-frame and HVAC or communication codes to identify which module rejected the compressor message.
- Compare live compressor speed and torque data with A/C demand and cooling performance, noting whether the compressor is being commanded on.
- Inspect accessible low-voltage compressor-control connectors and wiring for damage, corrosion, or poor contact.
- Check for related CAN or gateway faults and note whether the A/C system reports compressor or inverter shutdown.
- If the wiring and network are sound, verify compressor sensor data and module software compatibility using the manufacturer's procedure; do not probe high-voltage connections.
Common fixes
- Repair damaged or poorly connected low-voltage compressor-control wiring.
- Correct a poor control-module power, ground, or network connection.
- Correct software configuration after compressor module replacement.
- Repair or replace a faulty sensor input or compressor control module confirmed by testing.
- Repair a gateway or CAN fault if it is disrupting compressor messages.
Can I keep driving?
If the vehicle drives normally, it is generally safe to drive, but cabin cooling may be lost and defrosting may be less effective in humid weather. Stop if any high-voltage or general vehicle warning appears, or if the vehicle enters reduced power.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.