2001-2002 NB Miata EVAP Purge Valve, Canister, CDCV and Fuel-Cap Diagnosis

NC10-42-250B is currently cataloged as replacing NC49-42-250, NC10-42-250 and NC10-42-250A. The 1999 catalog changes engine-bay purge from Z504-18-741A to KLG5-18-741 at VIN 102379, while 2001-2002 uses KLG5-18-741. Do not present BP4W-13-970 versus BP5R-13-970 or BP4W-18-741A versus BP5R-18-741 as interchangeable supersession chains; the checked evidence shows year/production distinctions, not permission to cross-order.

Identify model year, US emissions label, VIN and standard/non-turbo engine before ordering. KLG5-18-741 controls vapor flow from the canister toward the intake; the rear CDCV closes the atmospheric side during the leak test; BP5R-13-970 stores vapor; the cap is one sealing boundary. Hoses, filler neck, non-return valve, chamber, catch tank, rollover/fuel shut-off hardware, air filter and FTP sensor remain separate leak or failure paths. A DTC or loose-cap message does not identify a failed component. Test the cap separately and leak-test the system using the vehicle-specific service procedure before replacing parts.

No evidence-gated direct aftermarket purge, CDCV or canister replacement was retained. Present checked new and used OEM paths only. Generic caps, universal valves and smoke-test equipment are not represented as direct replacement parts; diagnostic equipment does not establish the failed component.

This guide is only for US-market 2001-2002 naturally aspirated 1.8L NB cars. Late NA, 1999-2000 NB, 2003-2005 NB and Mazdaspeed use different identities, production branches or leak-test architecture. BP5R-18-741 is OEM-cataloged generically as a rear fuel-tank solenoid; its CDCV role is a strong location/function correlation, so verify VIN, installed number, connector and hose routing. A cap is only one possible sealing boundary, and no EVAP code proves a valve or canister failed. Work cold in a well-ventilated area with no smoking, flames or sparks; do not apply uncontrolled pressure or shop compressed air, and follow Mazda's vehicle-specific leak-test procedure. Seller prices and inventory are dated observations.

Supersede reviewed 23 unique research sources for this guide. 9 also appear above as a seller or official action and are not repeated here; 14 additional citations follow.

Research last verified 2026-07-27.

1. Emanualonline — 2001 2002 mazda miata mx 5 nb parts catalog emo 110023Open source
2. Emanualonline — mazda mx5 mx 5 miata 1990 to 1997 collision parts ipl manual emo 110021Open source
3. PartSouq — source pageOpen source
4. PartSouq — source pageOpen source
5. Charm — LocationsOpen source
6. Charm — Service and RepairOpen source
7. Charm — Evaporative System TestOpen source
8. Charm — Testing and InspectionOpen source
9. Charm — Using Leak TesterOpen source
10. Charm — Repair and DiagnosisOpen source
11. Charm — Testing and InspectionOpen source
12. Mazda USA — 2002 mx 5 miata owners manualOpen source
13. Klze — 00000 ALL IN ONEOpen source
14. MX 5NB — NB collision guidepdfOpen source