P0291 Engine Trouble Code
What is P0291?
The P0291 check-engine light can indicate issues ranging from minor (loose gas cap) to serious (catalytic converter failure). Professional diagnostic scanning at a dealer or shop will identify the exact cause and required repairs.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Code: | P0291 |
P0291 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
P0291 Code Structure
Understanding what each digit means in the P0291 powertrain trouble code:
| P | 0 | 2 | 9 | 1 |
|---|---|---|---|---|
| Powertrain Code | Intake Valve Control Solenoid Circuit Low | Manifold Absolute Pressure/Barometric Pressure Circuit High Input | Crankshaft Position Sensor A Circuit Malfunction | Crankshaft Position Sensor A Circuit Low Input |
How to Fix P0291
Diagnostic Steps:
Check if fuel pump primes when key is turned to ON. Measure fuel pressure and verify bright white-blue spark at all plugs. Also verify mechanical timing alignment.
Repair Solution:
VSS concerns may stem from noisy input signals caused by RFI/EMI from ignition wires, charging circuits, or aftermarket equipment. Verify VSS reads 0 mph when transmission is in Park.
Technical Notes:
P0291 DTC specifically relates to camshaft timing. When cam timing is over-retarded, the check-engine light illuminates and this code sets. Verify VCT solenoid operation and check for contamination.
P0291 Description
P0291 OBD-II Trouble Code: Code P0291 is triggered when the Engine Control Module (
Main Cause
The primary reason for P0291 OBD-II Engine Trouble Code is: Manifold Absolute Pressure/Barometric Pressure Circuit High Input.