P0AC4Hybrid/EV Powertrain Control Module Requested MIL Illumination
- Generic OBD-II code · Powertrain
- Matters for the ITP
- How the car detects it
- In many hybrids the hybrid powertrain controller has its own emission-related diagnostics but does not drive the malfunction indicator lamp itself. When it detects such a fault it sends a MIL request to the engine controller, which then stores P0AC4 as a pointer. GM documents this in its 2011, 2013, 2016 and 2019 hybrid tables: the engine controller watches the request message continuously once 3 seconds have passed after power-up and logs P0AC4 after one trip, listed as Type A but marked No MIL because the lamp is owed to the original fault. The real cause is therefore stored in the hybrid controller and must be read there. P0A7B is the equivalent request from the battery energy control module.
- What you may notice
- Check engine light on (caused by the underlying hybrid fault)
- Further codes present only in the hybrid controller
- Likely causes
- LikelyEmission-related fault stored in the hybrid controller
- RareRequest still present because codes were cleared only in the engine controller
- Inspection (ITP)
- Can matter for the ITP: it concerns the emissions system.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.