B0391 Engine Trouble Code
What is B0391?
B0391 indicates potential catalytic converter failure. If completely failed, your vehicle may not run properly and fuel economy will suffer significantly. Average replacement cost is $2,000–$2,140. This repair requires professional service and should not be delayed.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Code: | B0391 |
B0391 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
B0391 Code Structure
Understanding what each digit means in the B0391 body trouble code:
| B | 0 | 3 | 9 | 1 |
|---|---|---|---|---|
| Body Code | Intake Valve Control Solenoid Circuit Low | Throttle/Pedal Position Sensor/Switch A Circuit Intermittent | Crankshaft Position Sensor A Circuit Malfunction | Crankshaft Position Sensor A Circuit Low Input |
How to Fix B0391
Diagnostic Steps:
The catalytic converter has oxygen sensors before and after it. When warm and in closed-loop mode, the upstream O2 sensor reading should fluctuate, while downstream should remain steady.
Repair Solution:
A/C pressure sensor monitors refrigerant pressure changes. DTC sets when pressure change falls outside calibration. Verify A/C system function, refrigerant charge, and electrical connections.
Technical Notes:
For B0391, verify VCT solenoid operation. Look for stuck or sticking valves caused by contamination. Consult vehicle-specific repair manual for proper component testing procedures.
B0391 Description
B0391 engine trouble code is related to Crankshaft Position Sensor A Circuit Low Input.
Main Cause
The primary reason for B0391 OBD-II Engine Trouble Code is: Throttle/Pedal Position Sensor/Switch A Circuit Intermittent.