Cause
Fault stored in the hybrid powertrain control module
Another module reporting that the hybrid powertrain controller is itself carrying a fault, so the data it publishes cannot be relied on. It is a pointer rather than a diagnosis — the code says where to look, not what is wrong.
Reading it as a fault in the module is the mistake it exists to prevent. The hybrid controller coordinates the engine, the motors, the battery and the inverter, so a fault in any of them leaves it unable to answer normally, and the modules asking report invalid data. The originating code is inside the hybrid controller and is the one that matters.
So the order of work is fixed: read the hybrid module's own codes first. Diagnosing the reporting module is diagnosing a messenger. High voltage systems demand the manufacturer's isolation procedure before any physical work, and much of what these modules report — battery temperature, state of charge, contactor state — is genuinely dangerous to investigate casually. Establish what the controller is complaining about before touching anything.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
1 of the 3 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (3)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0AC4 Hybrid/EV Powertrain Control Module Requested Malfunction Indicator Lamp Illumination Likely for this code Moderate
- P0CA1 Drive Motor Control Module Requested Malfunction Indicator Lamp Illumination Likely for this code High
- U0293 Lost Communication With Hybrid/EV Powertrain Control Module Stop driving High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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