How to Fix P1121

🚨 Diagnostic Profile

Vehicle Make: Mazda

Code/Issue Name: Throttle Position Sensor (TPS) Signal Not Consistent With Mass Air Flow (MAF) Signal

This diagnostic trouble code indicates that the Powertrain Control Module (PCM) has detected a discrepancy between the throttle position sensor’s reported throttle opening angle and the airflow volume being measured by the mass air flow sensor. Under normal operating conditions, these two values should correlate directly — as the throttle opens wider, airflow should increase proportionally. When the PCM sees a mismatch (e.g., throttle wide open but low airflow reported, or vice versa), it flags this fault to prevent improper fuel trim calculations, which can cause rough idle, hesitation, stalling, or reduced power output.