01 Lubrication Systems: Everything You Need to Know • 02 Can Seafoam Fix Engine Problems? True Stories of Improved P… • 03 Experts Warn That A Small Everyday Driving Mistake Could En… • 04 What is Brake Disc Skimming and Why Do You Need It? • 05 What Are the Symptoms of a Failing Transmission Control Mod… • 06 How Reliable are BMW Cars? A Comprehensive Guide for Car Bu… • 07 B0028, B0029, and B0030: Right Front or Passenger Side Depl… • 08 What to Do If Your Car Starts and Then Stops • 09 Steering Systems: Parallelogram vs Rack and Pinion • 10 Common Car Part Issues and How to Fix Them •

DTC codes / U30xx · Network wiring and bus faults / U302C

U302CIgnition Output Off/On/Start

This code indicates that the powertrain control module (PCM) has detected an abnormal condition in the ignition output circuit, specifically related to the off, on, or start signal. The PCM monitors the ignition switch input and sets this code when the voltage signal does not match expected values for the current ignition state.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaNetwork wiring and bus faults

Symptoms you may notice

  • The engine may not start or may stall intermittently
  • The check engine light is illuminated
  • The ignition may not turn off properly, leaving accessories powered
  • Intermittent no-crank or slow crank conditions
  • Often no symptoms besides the warning light

Common causes, most likely first

  1. Faulty ignition switch
  2. Wiring damage or corrosion in the ignition circuit
  3. Poor connection at the PCM or ignition switch connector
  4. Defective PCM (rare)
  5. Blown fuse or fusible link in the ignition circuit
  6. Aftermarket accessories improperly wired into the ignition circuit

How to diagnose and fix it

  1. Verify battery voltage and condition, as low voltage can cause false codes
  2. Inspect ignition switch and related fuses for obvious damage or corrosion
  3. Check wiring and connectors between the ignition switch and PCM for continuity and shorts
  4. Test the ignition switch operation with a multimeter to confirm proper voltage signals in each position
  5. If wiring and switch are good, test the PCM inputs and outputs according to manufacturer procedures
  6. Replace faulty components as needed and clear the code to verify the repair

Ignition Switch Circuit Diagnostics

  • A common oversight is assuming the ignition switch is bad when the actual problem is a corroded connector or chafed wire hidden under the dash.
  • Aftermarket alarms or remote starters tapped into the ignition circuit often cause this code due to improper splicing.
  • The code can set intermittently if the ignition switch is worn internally, making contact only in certain positions.
  • Always check for technical service bulletins (TSBs) for your specific vehicle, as some models have known ignition switch issues.

Can I keep driving with U302C?

If the vehicle starts and runs normally, you can drive it to a repair shop, but avoid turning the engine off if you suspect the ignition switch may not restart it. If the engine stalls or fails to start, do not drive and seek immediate assistance.

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.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage