Damaged, chafed, or corroded wiring in the throttle position output circuit between the PCM and the electronic throttle body; Loose or contaminated electrical connector at the throttle body or PCM; Failed electronic throttle body actuator or internal position sensor; Short to ground on the throttle position output signal wire; Faulty powertrain control module (PCM) driver circuit, though this is less common; Water intrusion or corrosion inside the throttle body connector causing low signal voltage

DTC codes / P26xx · Computer and output circuits / P2621

P2621Throttle Position Output Circuit Low

Q: What does code P2621 mean?

Throttle Position Output Circuit Low. P2621 indicates that the powertrain control module (PCM) has detected an abnormally low voltage on the throttle position output circuit, which is the signal the PCM uses to command the electronic throttle actuator. The PCM compares the commanded throttle position with the actual throttle position sensor feedback, and when the output circuit voltage stays below the expected threshold, it sets this code and typically forces the engine into a reduced-power limp mode.

P2621 indicates that the powertrain control module (PCM) has detected an abnormally low voltage on the throttle position output circuit, which is the signal the PCM uses to command the electronic throttle actuator. The PCM compares the commanded throttle position with the actual throttle position sensor feedback, and when the output circuit voltage stays below the expected threshold, it sets this code and typically forces the engine into a reduced-power limp mode.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illuminated check engine light, often accompanied by the electronic throttle control (ETC) warning light
Reduced engine power or limp mode with a maximum speed or RPM limit
Poor or delayed acceleration when pressing the accelerator pedal
Engine may idle erratically or stall immediately after startup
Cruise control may become inoperative or disengage unexpectedly
Often no symptoms besides the warning light if the fault is intermittent

Common causes, most likely first

Damaged, chafed, or corroded wiring in the throttle position output circuit between the PCM and the electronic throttle body
Loose or contaminated electrical connector at the throttle body or PCM
Failed electronic throttle body actuator or internal position sensor
Short to ground on the throttle position output signal wire
Faulty powertrain control module (PCM) driver circuit, though this is less common
Water intrusion or corrosion inside the throttle body connector causing low signal voltage

How to diagnose and fix it

Connect a scan tool and record all stored and pending codes, then clear codes and test-drive to see if P2621 returns immediately or only under specific conditions
Visually inspect the throttle body connector and the PCM connector for corrosion, bent pins, or loose terminals, and repair as needed
Back-probe the throttle position output circuit at the throttle body and measure voltage with the key on and engine off, comparing to the manufacturer's specification
Perform a wiggle test on the harness while monitoring throttle position output voltage on the scan tool to reveal intermittent wiring faults
Check for continuity and short-to-ground on the signal wire between the throttle body and PCM using a digital multimeter
If wiring and connectors are good, substitute a known-good throttle body and recheck for the code before condemning the PCM
After repairs, clear codes, perform a throttle body relearn or idle relearn procedure if required, and verify the repair with a road test

What the throttle output circuit really does

P2621 is often set by a dirty or worn throttle body rather than a failed PCM, so cleaning the throttle plate and performing a relearn can resolve the code on high-mileage vehicles.
A low voltage on the output circuit can be caused by a short to ground in a harness that rubs against the engine block, which a visual inspection alone may miss without a wiggle test.
This code does not always mean the throttle body is defective; a weak battery or poor ground connection can cause the PCM to misread the output signal and set P2621.
Some vehicles require a throttle position sensor relearn after any throttle body service, and skipping that step will cause the code to return immediately even with good parts.
Intermittent P2621 codes that appear only in cold or wet weather often point to water intrusion in the throttle body connector rather than an internal component failure.

Can I keep driving with P2621?

Do not continue driving with an active P2621 because the vehicle may enter limp mode without warning, leaving you with severely reduced power in traffic. If the code is pending or intermittent and the car drives normally, limit driving to a short trip to a repair shop and avoid highways or heavy traffic.

Tools that help

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