P1491 Nissan Code - Vacuum Cut Valve Bypass Valve
Quick Answer
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. Common causes include Vacuum cut valve bypass valve, Vacuum cut valve, Bypass hoses for clogging. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P1491 Nissan indicates Vacuum Cut Valve Bypass Valve.
- Common causes
- Common causes include Vacuum cut valve bypass valve, Vacuum cut valve, Bypass hoses for clogging.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P1491 Nissan Description
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 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.
What are the Possible Causes of the DTC P1491 Nissan?
- 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 to Fix the DTC P1491 Nissan?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
There is a factory service bulletin for all 1998-2002 Nissan models.
1998-2002 Nissan Factory Service Bulletin OBDII Code P1491
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P1491 Nissan code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Information for Specific Nissan Models
- P1491 2002 Nissan Altima Sedan — Vacuum Cut Valve Bypass Valve
- P1491 2003 Nissan Altima Sedan — Vacuum Cut Valve Bypass Valve
- P1491 2000 Nissan Sentra — Vacuum Cut Valve Bypass Valve
- P1491 2001 Nissan Sentra — Vacuum Cut Valve Bypass Valve
- P1491 2002 Nissan Sentra — Vacuum Cut Valve Bypass Valve
Frequently Asked Questions about P1491 Nissan Code
1. What does OBDII code P1491 on a Nissan indicate?
The OBDII code P1491 on a Nissan refers to an issue with the Vacuum Cut Valve Bypass Valve.
2. What are the common symptoms of a Vacuum Cut Valve Bypass Valve problem?
Common symptoms of a Vacuum Cut Valve Bypass Valve issue include rough idling, stalling, and difficulty starting the vehicle.
3. What are the possible causes of OBDII code P1491 on a Nissan?
Possible causes of code P1491 on a Nissan include a faulty Vacuum Cut Valve Bypass Valve, vacuum leaks, or issues with the vacuum lines.
4. How can I diagnose a Vacuum Cut Valve Bypass Valve problem?
Diagnosing a Vacuum Cut Valve Bypass Valve problem involves checking the valve for proper operation, inspecting vacuum lines for leaks, and using a scan tool to read the trouble codes.
5. Can a Vacuum Cut Valve Bypass Valve issue affect the performance of my Nissan?
Yes, a Vacuum Cut Valve Bypass Valve problem can lead to poor engine performance, reduced fuel efficiency, and potential damage to other engine components if not addressed promptly.
6. How can I repair a Vacuum Cut Valve Bypass Valve issue?
Repairing a Vacuum Cut Valve Bypass Valve problem may involve replacing the faulty valve, repairing or replacing damaged vacuum lines, and clearing the trouble code with a scan tool.
7. Is it safe to drive my Nissan with OBDII code P1491 present?
While it may be safe to drive your Nissan with code P1491, it is recommended to address the issue as soon as possible to prevent further damage and ensure optimal performance.
8. Can I fix a Vacuum Cut Valve Bypass Valve problem myself?
Depending on your mechanical skills, you may be able to replace the Vacuum Cut Valve Bypass Valve or repair minor vacuum leaks yourself. However, if you are unsure, it's best to consult a professional mechanic.
9. How much does it cost to repair a Vacuum Cut Valve Bypass Valve issue on a Nissan?
The cost of repairing a Vacuum Cut Valve Bypass Valve problem can vary depending on the extent of the issue, the parts needed, and labor costs. It's advisable to obtain quotes from different auto repair shops.
10. How often does the Vacuum Cut Valve Bypass Valve need to be replaced?
The Vacuum Cut Valve Bypass Valve typically does not have a specific replacement interval and should only be replaced when it fails or shows signs of malfunction. Regular maintenance and inspections can help prevent unexpected issues.
Discuss the causes and fixes for P1491 Nissan OBDII Code
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I replaced the bypass valve connected to the solenoid as well as the valve on the evap canister, and I still am getting the 1491 code. I had someone check it, and there were no leaks, so is it the evap canister?
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did u get this fixed eventually. i am getting the same code on my 2002 Nissan Xterra. What else did you have to change apart from the bypass valve?
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check all 12V Evap. solenoid valves for proper function - replace the cut-valve(Non-electric) first---if EVAP codes continue, it will likely be your Fuel Vapor Canister(while my 24 year old canister showed no outward damage, and it appeared to be clear through air testing, there was some "old" wear & internal damage that was giving out the EVAP trouble codes to include P1491...
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