B1991 Engine Trouble Code
What is B1991?
With B1991, 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: | B1991 |
B1991 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
B1991 Code Structure
Understanding what each digit means in the B1991 body trouble code:
| B | 1 | 9 | 9 | 1 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | Injector Circuit Malfunction - Cylinders | Crankshaft Position Sensor A Circuit Malfunction | Crankshaft Position Sensor A Circuit Low Input |
How to Fix B1991
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:
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:
B1991 on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
B1991 Description
B1991 engine trouble code is related to Crankshaft Position Sensor A Circuit Low Input.
Main Cause
The primary reason for B1991 OBD-II Engine Trouble Code is: Injector Circuit Malfunction - Cylinders.