P2871: Mazda CW6A-EL oil-pump shift-valve diagnosis

P2871 is cataloged as clutch A performance or stuck disengaged. Mazda's CW6A-EL factory page uses a different application-specific description: oil-pump shift valve stuck on.

Confirm the transmission definition first

The monitor applies with the engine running, after driving in a specified gear, with ATF at least 20 °C and the listed speed-sensor fault exclusions. Its detection wording also references the relationship between vehicle and output-shaft speed. This source does not justify identifying a generic clutch A component on every vehicle with P2871.

Mazda inhibits the affected gear and i-stop. Possible causes include insufficient ATF, the pump shift valve and the control valve body. The actual fluid level is therefore a diagnostic branch before an assembly decision, rather than an optional general maintenance check.

Related code and fluid history change the route

The procedure checks P1738 first, then assesses ATF level. It distinguishes a level that was already correct from one that needed adjustment when interpreting the subsequent onboard test. That distinction can change whether the factory branch addresses the valve body or proceeds to a broader transaxle decision.

Professional verification uses the required warm-fluid condition and the exact CW6A-EL onboard procedure. Preserve the original level finding and companion code. The wording difference is a real limitation: this article explains Mazda's monitor and does not equate its pump valve with a universal clutch-A assembly.

Documented application

Mazda3 workshop manual 01/2019 onward, d9n1-1a-22d_ver10; TCM (CW6A-EL). Verify exact vehicle specification; this is a Mazda application example. Mazda factory diagnostic page, mirrored by CHARM.