Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota Matrix and 2003 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Read freeze frame data using hand-held tester or OBD II scan tool, as freeze frame data records engine conditions when malfunction is detected. When trouble shooting, it is useful for determining whether vehicle was running or stopped, engine was warmed up or not, air-fuel ratio was lean or rich, etc. at time of malfunction.

Check if there are any other DTCs being output (besides P0121). If only P0121 is output, replace EFI throttle position sensor. See REMOVAL & INSTALLATION - 4-CYLINDER article. If P0121 and other codes are output, diagnose and repair those codes first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .