P1491 2003 Nissan Altima Sedan 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 2003 Nissan Altima Sedan 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 2003 Nissan Altima Sedan 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 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:
What are the Possible Causes of the DTC P1491 2003 Nissan Altima Sedan?
- 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 2003 Nissan Altima Sedan?
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
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P1491 2003 Nissan Altima Sedan 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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Frequently Asked Questions about P1491 2003 Nissan Altima Sedan Code
1. What does the OBDII code P1491 mean on a 2003 Nissan Altima Sedan?
P1491 indicates a problem with the Vacuum Cut Valve Bypass Valve, which is part of the evaporative emissions control system (EVAP).
2. What are the common symptoms of code P1491?
Common symptoms include the check engine light turning on, a potential fuel odor, and possibly reduced fuel efficiency.
3. What causes the P1491 code to appear?
The most common causes are a faulty Vacuum Cut Valve Bypass Valve, a damaged or disconnected vacuum hose, or electrical wiring issues.
4. Can I drive my 2003 Nissan Altima with a P1491 code?
While the car may still drive normally, it is not advisable to ignore the code as it can impact emissions and may lead to further issues.
5. How do I diagnose the P1491 code?
Inspect the vacuum hoses for leaks, check the Vacuum Cut Valve Bypass Valve for proper operation, and test the electrical connections for continuity.
6. How do I fix the P1491 code?
Repairs may include replacing a faulty Vacuum Cut Valve Bypass Valve, repairing or replacing damaged vacuum hoses, or addressing wiring issues.
7. Where is the Vacuum Cut Valve Bypass Valve located on a 2003 Nissan Altima?
It is typically located near the EVAP canister, which is mounted under the car near the rear or in the engine bay.
8. How much does it cost to fix a P1491 code?
Repair costs can range from $50 to $250, depending on whether you need to replace the valve, hoses, or perform diagnostic work.
9. Can a loose gas cap trigger code P1491?
No, a loose gas cap typically triggers a different EVAP-related code, such as P0456 or P0442, rather than P1491.
10. Will clearing the code fix the issue permanently?
Clearing the code might temporarily turn off the check engine light, but the underlying issue must be addressed to prevent the code from returning.
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