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DTC codes / Chrysler codes / P1221

P1221 · ChryslerThrottle Position (TP) Sensor 1-2 Correlation

P1221 on a Chrysler vehicle means the powertrain control module (PCM) has compared the two throttle position (TP) sensor signals inside the electronic throttle body and found they do not agree within the expected tolerance. The PCM expects TP Sensor 1 and TP Sensor 2 to move in a correlated, mirrored fashion, and this code sets when that relationship is broken for a calibrated amount of time.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illumination of the check engine light, often with no other symptoms besides the warning light
  • Reduced engine power or limp-home mode with a noticeably sluggish throttle response
  • Unstable or surging idle as the PCM struggles to trust the throttle position signal
  • Hesitation or a flat spot during light acceleration from a stop
  • Transmission shifting harshly or holding gears longer than normal because shift scheduling relies on throttle position
  • In some cases the engine may stall or refuse to rev past a limited RPM threshold

Common causes, most likely first

  1. Carbon buildup or contamination on the throttle plate and bore causing the two TP sensor wipers to track unevenly
  2. A failing electronic throttle body assembly where one of the two internal TP sensors has worn or developed a dead spot
  3. Corroded, chafed, or pinched wiring in the TP sensor circuits between the throttle body and the PCM
  4. A poor ground or reference voltage supply shared by the throttle body sensors
  5. A PCM that has lost its throttle body adaptation values or has an internal driver fault
  6. Mechanical binding or sticking of the throttle shaft due to debris or a failing return spring
  7. Aftermarket or incorrectly installed throttle body that does not match the PCM calibration

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data for P1221, then check for related throttle codes before touching any parts
  2. Inspect the throttle body bore and plate for carbon deposits and clean them with throttle-body-safe cleaner if contamination is present
  3. Back-probe both TP sensor signal wires at the throttle body and compare their voltages through a slow sweep of the throttle plate by hand
  4. Check the sensor reference voltage and ground circuits for voltage drop and continuity back to the PCM
  5. Perform a throttle body adaptation or relearn procedure with a capable scan tool after cleaning or replacement
  6. Replace the electronic throttle body if one sensor track is proven faulty, then clear codes and verify correlation live data
  7. If wiring and throttle body are good, test the PCM circuits and consider PCM replacement only after all other causes are ruled out

What the correlation code really tells you

  • A dirty throttle body is the most common cause of P1221 on Chrysler vehicles, and a proper cleaning with a relearn often resolves the code without any parts replacement.
  • The two TP sensors are designed to read in opposite directions, so a technician must verify that Sensor 1 voltage rises while Sensor 2 voltage falls smoothly and that their sum stays within specification.
  • A scan tool that only shows throttle position percentage can hide the fault, so live voltage graphing of both sensors is essential for an accurate diagnosis.
  • This code does not automatically mean the throttle body is bad; chafed harness sections near the intake and corroded connector pins frequently mimic a failed sensor.
  • Replacing the throttle body without performing the PCM adaptation relearn will often set P1221 again immediately because the learned limits no longer match the new unit.

Can I keep driving with P1221?

You can usually drive the vehicle to a shop, but expect reduced power and possible limp-home mode, so avoid highway merging, heavy loads, and aggressive acceleration until the fault is repaired.

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.

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