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I got code P1490 - vacuum cut valve bypass valve on my Infiniti QX4 02', and now the engine light blinks on highway. what could be wrong and what is this vc/v bypass valve

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Posted on Jan 02, 2017

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SOURCE: check engine light on

Hi ,

I have a Haynes manual and it says that code P1490 identication is Vacuum Cut Valve Bypass Valve fault (California). I hope this helps.


Posted on Sep 22, 2008

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If its the 4JX diesel engine the crankshaft position sensor wants an adjustment as its going out of range.

Posted on Apr 20, 2009

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SOURCE: check engine on p1784 and p1490

they are mfg specific codes the p1490 code islow speedfan control relay circuit

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SOURCE: 2004 Dodge Ram. cuts out, check engine light always on

it's losing fuel pressure somewhere I would start with the filter check for any leaks then chek fuel rail poss band sensor at fuel pump also

Posted on Jul 27, 2010

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SOURCE: 2001 nissan altima

DTC P1441 - Vacuum Cut Valve Bypass Valve
Codes is for a very small leak code, usually the gas cap is the most common problem. Even if the cap looks ok it may need to be replaced. Als check the next items:
- Incorrect fuel tank vacuum relief valve.
- Incorrect fuel filler cap used.
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap.
- Leak is in line between intake manifold and EVAP canister purge volume control solenoid valve.
- Foreign matter caught in EVAP canister vent control valve.
- EVAP canister or fuel tank leaks.
- EVAP purge line (Pipe and rubber tube) leaks.
- EVAP purge line rubber tube bent.
- Blocked or bent rubber tube to EVAP control system pressure sensor.
- Loose or disconnected rubber tube.
- EVAP canister vent control valve and the circuit.

Te same problem we foudn in a Sentra 1.8L, then removed the vacuum cut valve bypass valve and tested it. With no voltage across the terminal we could blow through one hose and it comes out the other, with voltage we can feel the unit buzzing (it is essentially an electromagnet) but still no change, airflow is not stopped. Pulled the metal cage off and plunger dropped out. The exterior sealing o-ring looks okay. It seems like the plunger isn't sealing off internally when the coil is energized, even if pressed the plunger down by hand with good force it would not seal. That said I think I can safely state that this item is defective and the cause of the check engine code.

Our minimal issue is that the local Nissan dealer wants over $100 for solve this, that is a fairly common problem. If you can't seem to find an online source for this part,I suggest visit some junkyard.

Keep in mind that the P1441 is a very hard code to diagnose, as it's very "general". There are a list of things that can cause this code, and there is a Technical Service Bulletin issued by Nissan that states it can even be faulty ECM (on-board computer) programming.



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 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.

Here are the reasons that can cause this failure code:


This diagnostic process will require a scantool with advanced diagnostic capabilities. The vacuum bypass valve is more than likely the problem, but I cannot be sure until all of the components are properly tested. You can try to replace the valve but I cannot guarantee that this will solve your issue.

After that you replace this device, if the light goes out and stays off for 200-300 miles, then the vehicle will pass inspection. The vehicle must complete a drive cycle after the light goes off so that it will pass inspection. This is an emission issue, and will not cause any issue with driveability.
You should be able to remove the valve without dropping the rear suspension, but it is a tight fit. I would suggest a swivel socket to remove the bolts that hold the valve on.

Hope this helps.

Posted on Aug 10, 2011

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Hi ,

I have a Haynes manual and it says that code P1490 identication is Vacuum Cut Valve Bypass Valve fault (California). I hope this helps.


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