B1491 Engine Trouble Code
What is B1491?
With B1491, you may drive for several weeks with a malfunctioning MAF sensor, but expect decreased fuel economy and eventual stalling. Shop replacement costs $240–$400 depending on vehicle. The labour is straightforward, with most cost from the part itself.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Code: | B1491 |
B1491 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
B1491 Code Structure
Understanding what each digit means in the B1491 body trouble code:
| B | 1 | 4 | 9 | 1 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | O2 Sensor Heater Circuit Malfunction | Crankshaft Position Sensor A Circuit Malfunction | Crankshaft Position Sensor A Circuit Low Input |
How to Fix B1491
Diagnostic Steps:
Poor running symptoms align with MAP sensor malfunction. In some cases, a faulty MAP sensor will not trigger a code. The issue may represent separate wiring concerns requiring individual diagnosis.
Repair Solution:
Disconnected, dirty, or fouled spark plugs commonly prevent proper engine operation. Replace spark plugs every season or 25 hours. Verify proper spark plug gap. If plugs are good, check ignition components: spark plug wires, coils, and ignition module.
Technical Notes:
Parts or components should not be replaced based solely on B1491 DTC. Consult your vehicle service manual for proper diagnostic procedures, possible causes, and required testing before replacement.
B1491 Description
B1491 engine trouble code is related to Crankshaft Position Sensor A Circuit Low Input.
Main Cause
The primary reason for B1491 OBD-II Engine Trouble Code is: O2 Sensor Heater Circuit Malfunction.