Diagnostic Aids
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
This DTC uses two-trip detection logic. If problem exists with by-pass valve for HCAC system, it is possible that DTC P1431 will be set before DTC P1436 and DTC P1437. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.