P0AC4 — Hybrid/EV Powertrain Control Module Requested MIL Illumination
The hybrid powertrain control module has requested MIL illumination via the inter-module bus. Underlying fault is reported separately by the requesting module.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Hybrid powertrain cm
- Module communication bus
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Downstream fault in hybrid system
- Communication lag - MIL request stale
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.