Engine-Codes - Nissan - P1491 2001 NISSAN SENTRA

P1491 2001 NISSAN SENTRA - Vacuum Cut Valve Bypass Valve

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3  What is this?
Table of contents

P1491 2001 NISSAN SENTRA Possible 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

How is the P1491 2001 NISSAN SENTRA code repair?

Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

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

What is the cost to diagnose the P1491 2001 NISSAN SENTRA code

Labor: 1.0

The cost to diagnose the P1491 2001 NISSAN SENTRA code is 1.0 hour of labor. The auto repair labor rates vary widely across the country, and even within the same city. Most auto repairs shops charge between $75 and $150 per hour.
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When is the code detected?

Vacuum cut valve bypass valve does not operate properly.

Possible Symptoms

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

P1491 2001 NISSAN SENTRA Meaning

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:

More Information

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