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P1491 2001 Nissan Sentra Code - Vacuum Cut Valve Bypass Valve

- Code Popularity: 10,263 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P1491 2001 Nissan Sentra?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Vacuum cut valve bypass valve
  • Vacuum cut valve
  • Bypass hoses for clogging
  • EVAP control system pressure sensor and circuit
  • EVAP canister vent control valve
  • Hose between fuel tank and vacuum cut valve clogged
  • Hose between vacuum cut valve and EVAP canister clogged
  • EVAP purge port of fuel tank for clogging
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How to Fix the DTC P1491 2001 Nissan Sentra?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code Tech Notes

If the EVAP canister is OK, and there are no other visual damage to the EVAP system (e.g. loose or broken hoses), replacing the vacuum cut valve bypass valve takes care of the problem.

There is a factory service bulletin for the 2001 Nissan Sentra:
2001 Nissan Sentra Factory Service Bulletin OBDII Code P1491

Search for P1491 2001 Nissan Sentra Questions and Answers: Search here →

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1491 2001 Nissan Sentra code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

When is the Code Detected?

Vacuum cut valve bypass valve does not operate properly.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

Code P1491 2001 Nissan Sentra Description

The vacuum cut valve and vacuum cut valve bypass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister.
The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank. The vacuum cut valve bypass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis.
The vacuum cut valve bypass valve responds to signals from the Engine Control Module (ECM). When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then bypassed to apply intake manifold vacuum to the fuel tank.
Vacuum cut valve bypass valve location:

OBDII Code P1491 2001 Nissan Sentra - Vacuum Cut Valve Bypass Valve - AutoCodes.com
P1491 2001 Nissan Sentra Code - Vacuum Cut Valve Bypass Valve

Need More Information on the Code?

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