AutoCodes – Mercury – P1121 Mercury

P1121 Mercury Code - Throttle Position Sensor Inconsistent with Mass Air Flow Sensor

Quick Answer

The Powertrain Control Module (PCM) monitors a vehicle operation rationality check by comparing sensed throttle position to mass air flow readings. Common causes include Air leak between Mass Air Flow sensor and throttle body, Faulty Throttle Position Sensor, Throttle Position Sensor harness is open or shorted. 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: P1121 Mercury indicates Throttle Position Sensor Inconsistent with Mass Air Flow Sensor.
Common causes: Common causes include Air leak between Mass Air Flow sensor and throttle body, Faulty Throttle Position Sensor, Throttle Position Sensor harness is open or shorted.
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 3,866

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 Apr 25, 2019

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Cost to Diagnose
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Code P1121 Mercury Description

The Powertrain Control Module (PCM) monitors a vehicle operation rationality check by comparing sensed throttle position to mass air flow readings. If during key ON engine running self-test the comparison of the TP sensor and MAF sensor readings are not consistent with calibrated load values, the test fails and a diagnostic trouble code is stored in continuous memory.

OBDII Code P1121 Mercury - Throttle Position Sensor Inconsistent with Mass Air Flow Sensor - AutoCodes.com — P1121 Mercury Code - Throttle Position Sensor Inconsistent with Mass Air Flow Sensor

What does this mean?

What are the Possible Causes of the DTC P1121 Mercury?

Air leak between Mass Air Flow sensor and throttle body
Faulty Throttle Position Sensor
Throttle Position Sensor harness is open or shorted
Throttle Position Sensor circuit poor electrical connection
Damaged Mass Air Flow sensor

How to Fix the DTC P1121 Mercury?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1121 Mercury 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.