P1490 on Nissan: How to Diagnose & Fix
Secondary Air Relief / Injection Solenoid Circuit Malfunction
4 Nissan models · 4 documented issues · $80-$600 repair
P1490 on Nissan by model: symptoms, diagnosis and fix
On R50-generation Pathfinders the EVAP vacuum cut valve and its bypass solenoid are not under the hood — they sit outside on a steel bracket beneath the floor pan, just behind the driver's-side rear spring and forward of the fuel tank. Forum diagnosis of this code repeatedly puts the fault in that exposed pair: owners describe a green bypass solenoid and a white cut valve on a bracket that has spent its life in the road-salt spray thrown off the rear tire. Two things go wrong there. The solenoid's coil and its two-pin connector corrode until the ECM can no longer see a proper circuit, which is exactly what P1490 reports — the ECM is not getting the expected electrical feedback from the bypass valve driver circuit, as distinct from P1491, which is set when the valve is electrically alive but does not actually change the pressure in the tank during the leak test. The other failure is mechanical: grit and rust scale work into the valve body so the plunger sticks, or the short rubber hoses between the cut valve and bypass valve go hard and crack. Because this whole assembly only operates during the ECM's on-board EVAP diagnostic — the bypass valve is normally closed and opens only so intake manifold vacuum can be applied to the tank to check it for leaks — the driver usually notices nothing at all except the check engine light. There is no misfire, no drivability change, no fuel economy penalty. The code's real cost is a failed emissions inspection and a permanently lit MIL, and it tends to come back a few weeks after a code clear because the diagnostic only runs under a narrow set of fuel-level and drive-cycle conditions.
Common Symptoms
- Check engine light on with no drivability change
- Code returns days or weeks after being cleared
- Failed state emissions or OBD-II readiness inspection
- EVAP readiness monitor will not set to ready
- Corroded connector or rusted bracket at the rear underbody solenoid
How to Fix
Diagnose the circuit before buying anything. Raise the truck, find the bracket behind the driver's rear spring, and unplug the bypass solenoid. Bench-test it the way the factory manual specifies: apply battery voltage across the two terminals and confirm air passes between ports A and B, then remove voltage and confirm it seals; the valve must switch in one second or less. If it does not click at all, or does not seal, it is bad. If it clicks correctly on the bench, the fault is upstream — check the harness for a broken or chafed wire where it runs along the frame rail, and check the connector pins for green corrosion, spread terminals, or water sitting in the shell. A surprising number of these are fixed by cleaning and re-pinning the connector and packing it with dielectric grease rather than by replacing the valve. Where the solenoid is only clogged with debris rather than electrically dead, it can be taken apart with hand tools, cleaned, and reused — forum members do this routinely because the OEM part is expensive. If replacement is warranted, the Nissan control valve assembly is the 14933-series solenoid; budget for aftermarket equivalents at a fraction of dealer price. Two practical warnings: soak the bracket bolts with penetrating oil a day ahead, because the captive hardware is usually rusted solid and snaps easily, and replace the short connecting hoses at the same time since they are cheap and are half the failures. After the repair, clear the code and drive a full EVAP-enabling cycle — roughly a quarter to three-quarter tank of fuel and a cold start followed by steady cruising — before assuming the fix took, since the monitor will not run and re-confirm the repair on a short trip.
Sources for this issue (4)
The first-generation Xterra carries the same rear-mounted EVAP vacuum cut valve and bypass solenoid as its Frontier and Pathfinder siblings, and it fails the same way — only more often, because the Xterra's buyers actually drove them through the mud, snow and gravel the mounting location is least able to survive. The assembly is visible through the rear passenger wheel well, sitting near the fuel tank on the EVAP purge line between the tank and the charcoal canister. The vacuum cut valve blocks intake manifold vacuum from reaching the tank in normal operation; the bypass valve is a normally closed solenoid the ECM grounds to deliberately route that vacuum to the tank when it wants to run the EVAP leak test. P1490 is set on the electrical side of that: the ECM has driven the solenoid and has not seen the expected circuit response, which points at the solenoid coil, its connector, or the wire between it and the ECM. Owners report the light appearing with the truck driving completely normally, which is what makes this code frustrating — there is nothing to feel, nothing to hear, and no reason to suspect a part hanging under the back of the truck. In salt-belt trucks the connector is often full of corrosion and the bracket hardware is rusted; in trucks that see off-road use the valve body itself is packed with grit. A less common but real variant on this platform: a broken or missing exhaust tailpipe section has been known to route hot gas near the valve and heat-damage the plastic body outright, and that heat damage can extend to melted wiring.
Common Symptoms
- Check engine light with no change in how the truck drives
- P1490 returns after clearing
- Emissions test failure or EVAP monitor not ready
- Solenoid does not click when energized on the bench
- Rusted bracket and corroded two-pin connector at the rear of the vehicle
How to Fix
Start under the truck at the rear passenger-side wheel well rather than in the engine bay. Disconnect the solenoid and inspect the connector — corroded, spread or backed-out pins are common and are a cheap fix. Bench-test the valve by applying battery voltage across its terminals: airflow should pass between ports A and B with voltage applied and stop cleanly when it is removed, with the transition happening in under a second. Blowing through the ports with and without power is the field version of that test. A valve that does not click, sticks partially open, or leaks with voltage removed should be replaced; a valve that clicks correctly but still sets the code means the problem lies in the harness or the ECM driver circuit, so ohm the wire from the solenoid connector back to the ECM and look for chafe points along the frame. Where the valve is merely clogged, it can be disassembled, cleaned of rust scale and debris, and reinstalled — a well-documented forum repair that saves the cost of the part. Inspect and replace the short rubber lines between the cut valve and bypass valve while access is open; they harden and split at this age and will set EVAP leak codes even after a good solenoid is fitted. Soak the bracket fasteners with penetrating oil before attempting removal. Finally, verify the exhaust behind the muffler is intact and not blowing on the valve, and check the nearby wiring for heat damage if it is not. Clear the code and complete a drive cycle with the tank between roughly a quarter and three-quarters full so the EVAP monitor can actually run and confirm the fix.
Sources for this issue (4)
The evaporative emissions system on these trucks commonly develops faults from a sticking vent control valve, saturated charcoal canister, cracked hoses, or rust/dirt intrusion near the rear-mounted canister. Owners frequently report persistent check-engine lights and failed emissions inspections even though the truck otherwise drives normally. Nissan published EVAP-related service bulletins for leak and vent valve diagnosis on Frontier/Xterra-era trucks.
Common Symptoms
- check engine light
- failed emissions test
- fuel smell near rear of truck
- no drivability symptoms
- intermittent EVAP leak code
How to Fix
Diagnosis should include smoke testing the EVAP system, checking the vent control valve operation, inspecting canister hoses and purge lines, and verifying the gas cap seals properly. Repairs range from replacing the vent valve or damaged hoses to replacing the charcoal canister assembly if fuel saturation or contamination is present, then clearing codes and completing a drive cycle.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Nissan EVAP purge control valve 14930-5M00A
2000-2004 Frontier 2.4L and 3.3L applications on the live fitment table; confirm VIN and current supersession.
- Genuine Nissan EVAP pressure/drain-cut valve 14935-5M00B
Confirm VIN.
- Genuine Nissan EVAP canister 14950-5S601
Confirm VIN.
- Standard Motor Products CP3090 carbon canister
Direct listing covers 2001-2003 Frontier 2.4L and 2004 through 07/01/2004; verify the exact production date and live application before purchase.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipBefore replacing the canister, test the gas cap and vent valve first; many owners solve the code with the valve or cracked hose rather than the full canister.
Sources for this issue (1)
On the second-generation Altima the vacuum cut valve bypass solenoid lives just inside the rear wheel well, beside the fuel tank and the spare tire well, bolted to a small steel bracket under the body. It is one of the most rust-exposed electrical components on the car, and in the salt belt the bracket assembly typically corrodes badly — owners in the Northeast describe having to soak the fasteners for a day before the bolts will come out without snapping. The solenoid is normally closed and opens only when the ECM grounds it to admit intake manifold vacuum to the fuel tank for the on-board EVAP leak diagnostic. P1490 is the circuit-side complaint: the ECM drove the valve and the electrical feedback was wrong, which on this car is nearly always either a dead solenoid coil or a corroded connector, not a leak. The companion code P1491 is set when the valve is electrically fine but the tank does not respond to the test, so which of the two codes you have narrows the search considerably before you touch anything. Drivers notice essentially nothing beyond the check engine light — no stumble, no hard start, no smell of fuel — and the car will drive indefinitely with the code present. The consequence is an emissions failure and a MIL that hides any more serious code that might follow, and because the EVAP monitor only runs under specific fuel-level and temperature conditions, clearing the code buys a few days of a dark dash before it returns.
Common Symptoms
- Check engine light on, car drives normally
- Solenoid does not click when 12V is applied at the terminals
- Heavily rusted bracket and hardware at the rear of the car
- Emissions inspection failure
- Code reappears within days of being cleared
How to Fix
The diagnostic that settles this takes ten minutes. Jack the rear of the car, find the solenoid just inside the wheel well next to the tank, and unplug it. Apply battery voltage directly across the two terminals: a good valve clicks audibly and you can feel or hear the air passage open, and it should close again the instant power is removed. If there is no click, the solenoid is dead and needs replacing. If it clicks properly, put the meter on the harness instead — check for continuity from the solenoid connector back to the ECM, check the ground, and inspect the connector for the green corrosion and water intrusion that is endemic at this location. Cleaning the pins and sealing the connector with dielectric grease resolves a meaningful share of these without any parts at all. When the valve itself is bad, the part is the Nissan 14933-54U0A cut valve solenoid shared across Altima, Maxima and Pathfinder of this era; owners have sourced good used units for well under $50, and aftermarket replacements are widely available, while the genuine Nissan part runs considerably more. Before you start, soak the bracket bolts with penetrating oil the day before — rusted-in hardware, not the valve, is what turns this into a long job. Replace the short rubber hoses at the valve while you are there, since they crack at this age. Clear the code afterward and drive the car through a proper cold-start-plus-cruise cycle with a partly filled tank so the EVAP monitor can run and set to ready.
Sources for this issue (4)
- Check/Replace the Vacuum Cut Valve Bypass Valve on a 1998-2001 Nissan Altimaarticle
- P1490 - Vacuum cut valve bypass valve (circuit) - NissanHelp Altima Forumforum
- Code P1490 Nissan - Vacuum Cut Valve Bypass Valvearticle
- Genuine Nissan 14933-54U0A Cut Valve Solenoid (Altima / Maxima / Pathfinder)manufacturer
P1490 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1490 mean on a Nissan?
P1490 stands for "Secondary Air Relief / Injection Solenoid Circuit Malfunction." This is a manufacturer-specific code whose exact meaning varies by maker; on Ford it commonly indicates a fault in the secondary air relief solenoid circuit (part of the system that injects air into the exhaust to reduce cold-start emissions), while some applications use it for an EVAP or vacuum solenoid circuit. The computer detected that the solenoid circuit is open, shorted, or out of range. It is primarily an emissions-system fault and not an immediate drivability danger. Confirming the exact definition against the specific vehicle is recommended. On Nissan it is documented across 4 models: Pathfinder, Xterra, Frontier, Altima.
What are the most common causes of P1490?
The most common causes of P1490 are: Faulty secondary air (or vacuum) solenoid, Open or shorted wiring in the solenoid circuit, Corroded or loose electrical connector, Vacuum leak or collapsed vacuum hose, Failed secondary air pump or related relay, PCM driver circuit fault (less common). The specific cause varies by vehicle.
How much does it cost to fix P1490 on a Nissan?
Published repair estimates on Nissan range from $80 to $600 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P1490 on a different make?
View P1490 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.