C3903 Engine Trouble Code
What is C3903?
C3903 code can indicate a faulty oxygen sensor, which may eventually damage the catalytic converter (repair cost: $2,000–$2,200). Professional diagnosis costs around $200–$210. Oxygen sensors are often straightforward to replace — check your owner's manual for location and instructions. This issue should be addressed promptly to prevent further damage.
Code Information
| Code Type: | OBD-II Chassis (C) Trouble Code |
| System: | Chassis |
| Code: | C3903 |
C3903 Symptoms
Check Engine Light
Illuminated dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration
Starting Problems
Difficulty starting the engine
C3903 Code Structure
Understanding what each digit means in the C3903 chassis trouble code:
| C | 3 | 9 | 0 | 3 |
|---|---|---|---|---|
| Chassis Code | Ignition System Or Misfire | Injector Circuit Malfunction - Cylinders | Cold Start Injector 1 Malfunction | Exhaust Gas Recirculation Sensor B Circuit High |
How to Fix C3903
Diagnostic Steps:
Regarding C3903, carefully inspect the wire harness near the intake manifold bracket, best accessed from below near the oil filter. Look for chafing, pinching, or damaged insulation.
Repair Solution:
Gasoline engines use spark plugs to ignite fuel-air mixture. Proper timing ensures the explosion occurs when the piston is positioned correctly. Incorrect plug wire sequencing causes mistimed ignition, resulting in poor performance.
Technical Notes:
C3903 DTC specifically relates to camshaft timing. When cam timing is over-retarded, the check-engine light illuminates and this code sets. Verify VCT solenoid operation and check for contamination.
C3903 Description
C3903 engine trouble code is related to Exhaust Gas Recirculation Sensor B Circuit High.
Main Cause
The primary reason for C3903 OBD-II Engine Trouble Code is: Injector Circuit Malfunction - Cylinders.