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NorthPoleQX4

Loads of Codes

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hey everyone I was wondering if anyone knows the fix for the engine code P1490 'vacuum cut valve bypass valve', that's the only code that the Infiniti is throwing and I just don't know what actually to fix or replace. If all have any insight or knowledge that be greatly appreciated! thanks 

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Check out the Factory Services Manual for your truck (https://nicoclub.com/archives/infiniti-qx4-factory-service-manuals.html), then check out the EC chapter; subsections are sorted by P code.  Doesn't look like the 97 manuals mention it, but later models do.

 

That particular code deals with a bypass valve, which is a solenoid.  The FSM details the full/proper diagnostics, but the gist of it is that you need to inspect the solenoid.  Make sure it clicks with 12V applied and that the two ports on it open and close (easiest test is to just blow into a port with and without voltage applied).  The solenoids aren't cheap, but the ones on my trucks (04 Pathfinder, and a 98 Frontier where the charcoal canister ruptured and sent charcoal granules into the entire emissions system clogging hoses and valves) can be disassembled and reassembled with pliers and a screwdriver.  I've used a pin/needle to extract any tiny debris that's clogged them open/closed, then reassembled.  You also need to check for any loose/cracked hoses, cracked plastic, and potentially the cut valve itself (again, see the FSM for full steps). 

 

Green thing is the bypass solenoid, white thing is the cut valve.

96-98-Nissan-MAXIMA-Vacuum-Cut-Bypass-So

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So that is not the solenoid that is on top of the fuel tank?

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Nay.  It's behind the driver's rear spring, on a bracket under the floor pan:

 

02-BA325-C-B260-40-F8-8-E2-E-3-FAEB72-E1

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thank you much ill get to looking at this this weekend, I appreciate your insight. 

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