B1721 Engine Trouble Code
What is B1721?
B1721 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: | B1721 |
B1721 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
B1721 Code Structure
Understanding what each digit means in the B1721 body trouble code:
| B | 1 | 7 | 2 | 1 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | Fuel Rail Pressure Sensor Circuit Malfunction | Turbocharger Boost Sensor A Circuit Low | Crankshaft Position Sensor A Circuit Low Input |
How to Fix B1721
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:
Firing order is engineered to minimise vibration. Altering firing order results in mistimed ignition and poor engine operation. Consult vehicle-specific repair manual for correct firing order.
Technical Notes:
B1721 on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
B1721 Description
B1721 engine trouble code is related to Crankshaft Position Sensor A Circuit Low Input.
Main Cause
The primary reason for B1721 OBD-II Engine Trouble Code is: Fuel Rail Pressure Sensor Circuit Malfunction.