HIGH System: Throttle & Idle Control SAE J2012 Standard

P0121: Throttle/Pedal Position Sensor 'A' Circuit Range / Performance

The ECM detects that Throttle Position Sensor 1 reading does not correlate with calculated airflow (MAP / MAF) or exhibits erratic voltage jumps.

Driveability & Safety Advisory

Reduced throttle response. Drivable only at low speeds.

Official Manufacturer TSB Advisories

GM 08-06-04-041 Target: 2007–2011 Chevrolet Impala / Malibu

Factory Condition: Throttle body plate carbon buildup causes physical binding of the throttle shaft.

OEM Service Remedy: Clean throttle body bore and perform throttle position idle relearn.

Physical Component Location & Service Access

Mounted on throttle body inlet.

Electrical Specifications & Live PID Benchmarks

Scan Tool Live Data Targets

TPS 1 Voltage at Idle: 0.65V – 0.85V (smooth climb to 4.3V at WOT)

Digital Multimeter (DMM) Specs

TPS 5V Reference: 4.95V – 5.05V

Signal Wire: Smooth sweep without resistance spikes

Documented Model-Specific Case Studies

2009–2014 Dodge Ram 1500 (5.7L Hemi)

Root Cause: Worn throttle body electronics.

Verified Fix: Replace throttle body assembly.

Technician Inspection & Testing Workflow

Graph TPS 1 on scan tool.

Sweep pedal slowly.

Inspect for carbon deposits.

Cost Breakdown

DIY Replacement Parts: $65 – $170

Independent Repair Shop (Parts + Labor): $280 – $550

Standard Diagnostic Time: 1.0 – 2.0 Flat-Rate Hours

Tools & Parts Matrix

Recommended Parts: Throttle body, Gasket

Required Test Tools: Scanner, Multimeter, Basic tools

Diagnostic Questions & Answers

Will cleaning the throttle body fix P0121?

If the cause is mechanical binding from carbon deposits, cleaning will fix it. If the cause is worn electrical contact tracks inside the sensor, replacement is required.