Diagnostic procedure

WARNING: This page is about a different car, the 2004 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: DTC P0421: Diagnostic Procedure Chart (Steps 1-8)

Courtesy of MAZDA MOTORS CORP.

Fig 1: DTC P0421: Diagnostic Procedure Chart (Steps 1-6)

Courtesy of MAZDA MOTORS CORP.

Fig 2: DTC P0421: Diagnostic Procedure Chart (Steps 7 & 8)

Courtesy of MAZDA MOTORS CORP.