AutoCodes – GMC – P1221 GMC

P1221 GMC Code - Throttle Position Sensor 1- 2 Correlation

Quick Answer

The Throttle Position (TP) Sensor is mounted on the throttle body of the Throttle Actuator Control (TAC) assembly. Common causes include Faulty Throttle Position (TP) Sensor, Throttle Position (TP) Sensor harness is open or shorted, Throttle Position (TP) Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1221 GMC indicates Throttle Position Sensor 1- 2 Correlation.
Common causes: Common causes include Faulty Throttle Position (TP) Sensor, Throttle Position (TP) Sensor harness is open or shorted, Throttle Position (TP) Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 24,907

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 15, 2019

Description
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
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Code P1221 GMC Description

The Throttle Position (TP) Sensor is mounted on the throttle body of the Throttle Actuator Control (TAC) assembly. The sensor is actually 2 individual throttle position sensors within 1 housing. Two separate signal circuits, a low reference circuit, and a 5-volt reference circuit are used in order to connect the TP sensor assembly and the TAC module. The TP sensor signal voltage increases as the throttle opens. The signal circuit for TP sensor is pulled up to 5-volt reference voltage.

OBDII Code P1221 GMC - Throttle Position Sensor 1- 2 Correlation - AutoCodes.com — P1221 GMC Code - Throttle Position Sensor 1- 2 Correlation

What does this mean?

What are the Possible Causes of the DTC P1221 GMC?

Faulty Throttle Position (TP) Sensor
Throttle Position (TP) Sensor harness is open or shorted
Throttle Position (TP) Sensor circuit poor electrical connection

How to Fix the DTC P1221 GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1221 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.