Faulty Throttle Position Sensor 1 (worn tracks or internal failure); Corroded, loose, or damaged electrical connector at the TP sensor; Chafed or broken wires in the TP sensor circuit (signal, ground, or reference voltage); Contaminated or sticking throttle body causing the sensor to read out of range; PCM software issue or internal fault (rare, but possible on some Chrysler models); Poor ground connection at the throttle body or engine block

DTC codes / Chrysler codes / P1120

P1120 · ChryslerThrottle Position (TP) Sensor 1 Circuit

Q: What does code P1120 mean?

Throttle Position (TP) Sensor 1 Circuit. P1120 on Chrysler vehicles indicates that the powertrain control module (PCM) has detected an out-of-range or implausible signal from Throttle Position (TP) Sensor 1, which is the primary sensor used to determine throttle blade angle. The PCM compares this signal against expected values from the throttle pedal and other sensors, and when the voltage or rationality check fails, it stores this code and typically illuminates the check engine light.

P1120 on Chrysler vehicles indicates that the powertrain control module (PCM) has detected an out-of-range or implausible signal from Throttle Position (TP) Sensor 1, which is the primary sensor used to determine throttle blade angle. The PCM compares this signal against expected values from the throttle pedal and other sensors, and when the voltage or rationality check fails, it stores this code and typically illuminates the check engine light.

SystemPowertrain

Code typeChrysler specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Check engine light illuminated, often with no other noticeable symptoms
Reduced engine power or limp mode, where the throttle responds sluggishly or not at all
Erratic or surging idle, or stalling when coming to a stop
Poor acceleration or hesitation during acceleration
Transmission may shift harshly or refuse to shift due to incorrect throttle input
Cruise control may be inoperative or disengage unexpectedly

Common causes, most likely first

Faulty Throttle Position Sensor 1 (worn tracks or internal failure)
Corroded, loose, or damaged electrical connector at the TP sensor
Chafed or broken wires in the TP sensor circuit (signal, ground, or reference voltage)
Contaminated or sticking throttle body causing the sensor to read out of range
PCM software issue or internal fault (rare, but possible on some Chrysler models)
Poor ground connection at the throttle body or engine block

How to diagnose and fix it

Use a scan tool to read live TP sensor 1 voltage and compare it to TP sensor 2 (if equipped) throughout the throttle range; look for dead spots or irrational readings
Visually inspect the TP sensor connector and wiring for corrosion, loose pins, or chafing, and repair as needed
Check reference voltage (typically 5V) and ground at the sensor connector with a multimeter; repair any wiring faults
Clean the throttle body and perform a throttle relearn procedure if contamination is found
Replace the Throttle Position Sensor 1 if voltage tests confirm it is faulty
If the sensor and wiring test good, check for PCM software updates or a faulty PCM
Clear the code and perform a road test to verify the repair and ensure the code does not return

Common Misdiagnosis Traps for P1120

A dirty throttle body can cause the TP sensor to read outside its expected range at closed throttle, setting P1120 even though the sensor itself is fine; cleaning and relearning often resolves the code.
On many Chrysler vehicles, TP sensor 1 and 2 are redundant and oppose each other; a failure in one sensor can set P1120 while the other sensor still provides a usable signal, so comparing both is critical.
Wiring harness damage near the throttle body is common due to heat and vibration, and a visual inspection alone may miss internal wire breaks; a wiggle test with a multimeter is often needed.
After replacing the TP sensor or throttle body, a throttle relearn procedure with a capable scan tool is required on many Chrysler models to prevent the code from returning.
P1120 can be set by a low battery or charging system issue that causes voltage spikes, so always check battery health and grounds before condemning the sensor.

Can I keep driving with P1120?

You can usually drive the vehicle to a repair shop, but expect reduced power and possible limp mode; avoid heavy acceleration and highway driving until the fault is repaired, as the vehicle may enter limp mode unexpectedly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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