P2621: Throttle Position Output Circuit Low

P2621 flags the throttle position output line as shorted to ground or reading below its permitted voltage band. A receiving module such as a transmission controller would then see a value that looks like a fully closed throttle all the time. No carmaker publishes a code-specific description with limits; the CARB requirement for output monitoring and GM's output-driver tests on the crank signal (0.5 ohm toward ground counted as a short, 40 failures in 50 samples) illustrate the usual method, but they are an analogy, not a documented P2621 strategy. Check the wire between the two modules for chafing against body ground and the connectors for corrosion before suspecting either controller. Compared with P2620 (open line) and P2622 (short to supply), the receiver here gets a steady low level.

High severity. Can I keep driving?Be careful: the car may suddenly lose power. If it goes into limp mode, get off the highway and calmly make your way to a repair shop.

Symptoms

Stored code in the engine module
Receiver behaves as if the throttle were always closed (late or odd shifts)

Most likely causes

Output wire chafed against body ground
Corrosion bridging the output pin to ground
Shorted input in the receiving module

What to check, in order

Start with the simplest. You can tick off each step.

Check the pedal and throttle connectors
With the connector unplugged, check whether the signal wire is making contact with ground.
Use live data to confirm that both sensors rise smoothly and consistently
Clean the throttle if it has carbon buildup
Run the relearn procedure with the scanner if the manufacturer requires it
Replace the part identified by the diagnosis

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P2621 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
6: Control modules and outputs
21: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2621?

Be careful: the car may suddenly lose power. If it goes into limp mode, get off the highway and calmly make your way to a repair shop.

What causes code P2621?

The most common causes are: output wire chafed against body ground; corrosion bridging the output pin to ground; shorted input in the receiving module.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.