U350A: Control Module Input Power C Circuit High
What to do
Have the charging system checked promptly — this one points at the alternator rather than at wiring.
Too much voltage is harder on a car than too little. It cooks the battery and stresses electronics throughout the vehicle, so the cost of leaving it is not limited to the part that reported it. If the headlights seem unusually bright, or brighten noticeably with engine speed, mention that.
A charging system test is quick and most garages will do it while you wait. That is the right next step rather than a diagnostic hunt.
What this code means
The control module's input power circuit C is reading high.
U35xx continues the supply story U30xx opens, and adds the detail that makes it diagnosable.
Where U3006 says a feed is open, this range says how it is wrong — out of range, low, high, or intermittent. That distinction is the diagnosis, because each points somewhere different:
- Low is resistance in the supply path: a corroded fuse holder, a tired connector, a splice gone high-resistance. The commonest by a wide margin.
- High points at the charging system rather than the wiring, and matters more than it sounds — overvoltage damages electronics across the whole car, not just this module.
- Range/performance means the voltage is present but behaves implausibly: not tracking the rest of the system, or not moving when it should.
- Intermittent is a connection rather than a component. A part that has failed stays failed; a supply that comes and goes with vibration, temperature or road surface is a joint.
Intermittent is the one people chase for weeks. The productive test is to reproduce it — wiggle the harness and flex the connector with the circuit live and being watched — rather than to measure a circuit that is behaving itself at the moment of testing.
High points away from this module entirely and at the charging system. Overvoltage is not a local problem — it stresses every electronic component in the vehicle, cooks the battery, and shortens the life of things that will fail expensively later. A car genuinely charging high should be seen promptly, and the regulator or alternator is where the answer is.
Likely causes
Start here
- Charging system overvoltage · moderate
- Faulty alternator · moderate
Less common
- Corroded or loose connector · easy
- Failed power or earth supply to the module · moderate
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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