P2621: Throttle Position Output Circuit Low

What it means

The throttle position output circuit voltage is below the expected level. This code does not identify a particular downstream module or failed component.

At a glance

• Usually lights the check-engine light

How it works

The throttle position output circuit sends a throttle-position signal to other vehicle electronics, and the code does not identify a particular receiving module. P2621 sets when the output voltage is lower than expected, which can result from a short to ground, a failed output buffer, or a poor connection.

Common causes

Most likely first.

1. Output wire shorted to ground
2. Output buffer transistor failed
3. Connector pins corroded - high contact resistance

Symptoms

• Check-engine light
• Reduced engine power or sluggish throttle response

How to diagnose it

1. Review freeze-frame and live data to see how throttle-position output behaved when P2621 set and whether engine response changed.
2. Inspect the output wire and connectors for chafing to ground, corrosion, loose pins, or other damage.
3. Use the wiring diagram to test the output circuit for a short to ground and compare readings with the manufacturer's specification.
4. Check connector contact and circuit continuity to identify excessive resistance or an open connection.
5. If the circuit and connections pass, test the output buffer or control module according to the manufacturer's procedure.

Common fixes

• Clean and secure corroded or loose output-circuit connector pins.
• Repair output wiring shorted to ground or damaged by chafing.
• Repair or replace the output buffer or control module if testing confirms failure.

Can I keep driving?

Drive only if throttle response is steady and predictable, and avoid overtaking or other situations that need rapid acceleration. Stop safely if power becomes severely limited or throttle response is erratic, because the output signal may fail further.