A short to battery positive voltage on the circuit C wiring, often from chafed insulation or a pinched harness; A faulty voltage regulator in the alternator causing system voltage to run high across the entire electrical system; A bad ground connection for the module, which raises the reference voltage the module sees on its power input; Water intrusion or corrosion in a connector on the circuit C power feed, creating a partial short; An internal fault in the control module itself, where its voltage sensing circuit misreads a normal supply; A misinstalled or incorrect fuse or relay that backfeeds voltage onto the circuit C feed; A failing battery or loose battery terminal causing voltage spikes that the module logs as an overvoltage event

DTC codes / U35xx · Network communication / U350A

U350AControl Module Input Power C Circuit High

Q: What does code U350A mean?

Control Module Input Power C Circuit High. U350A indicates that a control module has detected an abnormally high voltage on its input power circuit C, which is a dedicated power feed used by that module. The module's internal voltage monitor saw the supply exceed its expected operating range, so it flagged the fault and may have disabled certain functions to protect its circuitry.

U350A indicates that a control module has detected an abnormally high voltage on its input power circuit C, which is a dedicated power feed used by that module. The module's internal voltage monitor saw the supply exceed its expected operating range, so it flagged the fault and may have disabled certain functions to protect its circuitry.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

Symptoms you may notice

Illumination of the check engine light or a module-specific warning lamp
Often no symptoms besides the warning light, especially if the module still powers up on another feed
Intermittent or complete failure of the affected module's functions, such as lighting, climate control, or body controls
Electrical accessories on the same power circuit behaving erratically or staying on when they should be off
Battery drain or a blown fuse if the high voltage condition is caused by a short to power
Communication loss with the affected module on the network, leading to multiple unrelated warning lights

Common causes, most likely first

A short to battery positive voltage on the circuit C wiring, often from chafed insulation or a pinched harness
A faulty voltage regulator in the alternator causing system voltage to run high across the entire electrical system
A bad ground connection for the module, which raises the reference voltage the module sees on its power input
Water intrusion or corrosion in a connector on the circuit C power feed, creating a partial short
An internal fault in the control module itself, where its voltage sensing circuit misreads a normal supply
A misinstalled or incorrect fuse or relay that backfeeds voltage onto the circuit C feed
A failing battery or loose battery terminal causing voltage spikes that the module logs as an overvoltage event

How to diagnose and fix it

Perform a battery and charging system test, checking for overcharging above 15 volts with the engine running
Inspect the circuit C wiring and connectors for chafing, corrosion, or signs of a short to power, repairing as needed
Check the module's ground connections for cleanliness and tightness, and measure voltage drop on the ground side
Measure voltage on the circuit C feed at the module connector with the key on and engine running, comparing to battery voltage
Disconnect the module and check for backfeeding voltage on circuit C from other circuits or a faulty relay
If wiring and supply voltage are correct, substitute a known-good module or perform a module reflash per manufacturer guidance
Clear the code and verify the repair with a test drive and a scan tool recheck of the module's live voltage data

High voltage faults are not always the module

A failing alternator regulator can push system voltage high enough to set overvoltage codes in several modules at once, so always check charging voltage before condemning a control module.
A poor ground on the module raises the voltage the module sees on its power input relative to its ground reference, which can set a high-voltage code even when battery voltage is normal.
Technicians often replace the control module first, but a chafed wire shorting to a nearby power circuit is a more common cause of a high-voltage input code.
This code can appear after jump-starting a vehicle with the booster cables connected incorrectly, which sends a voltage spike through the module's power feed.
Some modules set this code intermittently from voltage spikes caused by a loose battery terminal, and the code may never return once the terminal is cleaned and tightened.

Can I keep driving with U350A?

You can usually drive the vehicle to a repair shop, but avoid long trips and keep an eye on the charging system gauge if equipped. If the battery warning light is also on or electrical functions are failing, stop driving and have the charging system checked immediately.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.