Using SUZUKI Scan Tool

Connect SUZUKI scan tool to DLC (1) with ignition switch OFF.
Check "TP Sensor Volt" value displayed on scan tool under the following each condition.
If measured value is out of specified range, check TP sensor referring to Step 12 of DTC P0121: THROTTLE POSITION SENSOR CIRCUIT RANGE / PERFORMANCE .

If OK, check wire harness of TP sensor.

Also check that "TP Sensor Volt" value varies according to throttle valve opening linearly. If not, it is possible that TP sensor has failed. Replace.

Special Tool
1. SUZUKI scan tool
  TP sensor voltage
  
  When throttle is fully close: 0.70 +/- 0.15 V
  
  When throttle is fully open: 4.0 +/- 0.5 V
  
  Fig 1: Connecting SUZUKI Scan Tool To DLC
  Courtesy of SUZUKI OF AMERICA CORP.