Code Definition

P1121 — TP Sensor Circuit Intermittent Voltage High

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

About P1121

P1121 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 P1121 is stored, the module has detected a signal or supply voltage higher than the expected operating range; and 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.

P1121 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 Engine Control Module (ECM) monitors the Throttle Position (TP) sensor signal voltage to determine throttle plate angle for fuel delivery and ignition control. DTC P1121 is set when the ECM detects an intermittent high voltage condition on the TP sensor signal circuit, where the signal momentarily spikes toward or beyond its upper limit (near 5 volts) instead of reporting a stable value that matches throttle angle. On Isuzu electronic throttle applications the TP sensor is integrated into the throttle body and shares a 5 volt reference and ground with the ECM, so a brief loss of ground or ...

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