Dirty or contaminated throttle body causing the throttle plate to stick or bind; Worn or faulty throttle position sensor (TPS) internal tracks; Damaged or corroded wiring and connectors in the TPS circuit; Poor electrical ground at the throttle body or engine block; Failed throttle actuator control (TAC) motor or its associated circuits; ECM software calibration issue requiring a reflash or update; Mechanical binding in the accelerator pedal assembly or cable (on older models)

DTC codes / Jaguar codes / P1251

P1251 · JaguarThrottle Position

Q: What does code P1251 mean?

Throttle Position. P1251 on a Jaguar indicates that the engine control module (ECM) has detected an implausible signal or out-of-range condition from the throttle position sensor (TPS) circuit. The ECM compares the TPS voltage against expected values derived from other sensors, such as the mass airflow (MAF) sensor and engine speed, and sets this code when the correlation falls outside the acceptable window.

P1251 on a Jaguar indicates that the engine control module (ECM) has detected an implausible signal or out-of-range condition from the throttle position sensor (TPS) circuit. The ECM compares the TPS voltage against expected values derived from other sensors, such as the mass airflow (MAF) sensor and engine speed, and sets this code when the correlation falls outside the acceptable window.

SystemPowertrain

Code typeJaguar specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Intermittent or sustained reduced engine power, sometimes entering limp mode
Poor throttle response or hesitation during acceleration
Rough idle or stalling when coming to a stop
Automatic transmission may shift harshly or refuse to downshift smoothly
Cruise control may become inoperative or disengage unexpectedly

Common causes, most likely first

Dirty or contaminated throttle body causing the throttle plate to stick or bind
Worn or faulty throttle position sensor (TPS) internal tracks
Damaged or corroded wiring and connectors in the TPS circuit
Poor electrical ground at the throttle body or engine block
Failed throttle actuator control (TAC) motor or its associated circuits
ECM software calibration issue requiring a reflash or update
Mechanical binding in the accelerator pedal assembly or cable (on older models)

How to diagnose and fix it

Use a scan tool to read live TPS voltage and compare it to the specified range through the full sweep of the accelerator pedal.
Visually inspect the throttle body, TPS connector, and wiring harness for corrosion, chafing, or loose pins; repair as needed.
Clean the throttle body with approved cleaner and perform a throttle body adaptation reset using a diagnostic tool.
Backprobe the TPS signal, reference voltage, and ground wires to check for voltage drops or intermittent opens while wiggling the harness.
Check the accelerator pedal position sensor (APP) readings for correlation with TPS; replace the APP sensor if erratic.
If the TPS signal is erratic but wiring is good, replace the throttle position sensor or the complete throttle body assembly as required.
After repairs, clear the code and perform a road test with live data monitoring to confirm the TPS signal remains within specification.

Throttle body carbon is a frequent culprit

A throttle body that is only slightly carboned up can cause the TPS voltage to fall outside the expected range at closed throttle, setting P1251 without any driveability complaint.
On many Jaguars, the TPS is integrated into the throttle body and cannot be replaced separately, so technicians often replace the entire unit when the sensor fails.
A weak battery or poor charging system can cause voltage spikes that corrupt the TPS signal and set P1251 intermittently, so always check battery condition and grounds first.
The ECM may set P1251 as a result of a miscalibrated throttle body after a battery disconnect or replacement; a relearn procedure is often required.
P1251 can be triggered by a sticking throttle plate due to a failing throttle actuator motor, which may not set a separate TAC motor code until the failure is more advanced.

Can I keep driving with P1251?

You can usually drive the car to a workshop, but avoid aggressive acceleration and be prepared for the engine to enter limp mode with reduced power. If the throttle response becomes unpredictable or the engine stalls repeatedly, stop driving and arrange a tow.

Tools that help

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Guidance is general and written for Jaguar vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.