P2621 moderate

Throttle Position Output Circuit Low

The P2621 code means the vehicle's onboard diagnostic system has detected: Throttle Position Output Circuit Low. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $100 - $700 (parts and labor)

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Common Symptoms

Transmission upshifts too early
Traction control overactive
Poor acceleration response
Cruise control disengages

Probable Causes (Ranked by Likelihood)

Short to ground in throttle output wiring Very High
Receiving module pulling signal low High
ECM output driver shorted low Moderate
Corroded output circuit connector Low

Step-by-Step Diagnostic Procedure

Check throttle output circuit for short to ground
Compare ECM throttle input to output signal
Disconnect receiving modules to isolate short
Inspect connectors for corrosion

Frequently Asked Questions

Why does my car shift too early with P2621?

The low signal makes the transmission module think the throttle is barely open, so it upshifts early for fuel economy. The module does not know the driver is actually demanding acceleration.

Can P2621 cause sluggish acceleration?

Indirectly, yes. The transmission shifts too early for the driving conditions, making the vehicle feel sluggish even though the engine itself may be producing normal power.

How do I test the throttle output circuit?

Use a scan tool to read throttle position at the ECM, then check the output signal at the receiving module connector. They should match proportionally.