C0491 Engine Trouble Code
What is C0491?
C0491 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: | C0491 |
C0491 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
C0491 Code Structure
Understanding what each digit means in the C0491 chassis trouble code:
| C | 0 | 4 | 9 | 1 |
|---|---|---|---|---|
| Chassis Code | Intake Valve Control Solenoid Circuit Low | O2 Sensor Heater Circuit Malfunction | Crankshaft Position Sensor A Circuit Malfunction | Crankshaft Position Sensor A Circuit Low Input |
How to Fix C0491
Diagnostic Steps:
Regarding C0491, 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:
Verify all electrical connections are clean and tight. Check for damaged wiring, especially in high-heat or high-vibration areas. Use manufacturer wiring diagrams for accurate diagnosis.
Technical Notes:
C0491 on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
C0491 Description
C0491 engine trouble code is related to Crankshaft Position Sensor A Circuit Low Input.
Main Cause
The primary reason for C0491 OBD-II Engine Trouble Code is: O2 Sensor Heater Circuit Malfunction.