P0A1E: Starter/Generator Control Module
What to do
Stop-start refusing to operate is often the first and only symptom — the car is protecting its ability to restart. It will usually keep driving normally, but have it checked: the same machine is doing your charging. A conventional twelve-volt starter is still fitted on most mild hybrids, so a no-start is unusual with this code alone.
What this code means
The module controlling the starter/generator has failed its self-check.
This code belongs to the mild hybrid, where one belt-driven machine replaces both the alternator and, for most restarts, the starter motor. That double duty is what makes the failure picture distinctive: the same fault takes out charging and restarting together, and the first symptom most owners notice is the quietest one — stop-start silently giving up. The system stops switching the engine off at junctions, nobody is told why, and the car otherwise drives normally.
The module itself is usually integrated into the starter/generator or mounted beside it, working at forty-eight volts on most modern installations. Supply and earth checks come first, as with every module self-check in this range — and belt condition is worth a look too, since a slipping belt makes the machine underperform in ways the module reports as its own trouble.
Likely causes
Start here
- Failed power or earth supply to the module · moderate
Less common
- Faulty motor generator · specialist
- Module software fault needing an update · specialist
- Corroded or loose connector · easy
Symptoms
Components involved
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.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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