Code Definition

P1221 — Throtle motor position sensor 1/2 signal fault

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Isuzu

About P1221

P1221 is a manufacturer-specific powertrain diagnostic trouble code recorded for Isuzu vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1221 is stored, the module has detected a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1221 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The electronic throttle body uses two throttle position sensors whose signals the ECM continuously compares to confirm the throttle plate angle. DTC P1221 sets when the ECM detects that the throttle position sensor 1 and sensor 2 signals do not correlate within the expected relationship, indicating one or both signals are reading incorrectly. The sensors are designed to move with a fixed relationship, often one rising while the other falls, so a loss of correlation tells the ECM it cannot trust the throttle feedback. The system normally enters a reduced power mode, and the driver may experienc...

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