P2621 code meaning
Throttle Position Output Circuit Low
What P2621 means
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.
P2621 at a glance
- Check engine lightUsually not
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2621
- Stored code in the engine module
- Receiver behaves as if the throttle were always closed (late or odd shifts)
Common causes of P2621
- Most likelyOutput wire chafed against body ground
- PossibleCorrosion bridging the output pin to ground
- Less likelyShorted input in the receiving module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Control moduleSignal output bufferWiring harness
What each part of P2621 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 6 | Area: computer (engine control module) and output circuits. |
| 21 | The exact fault in that area. |
What to do next
- Note P2621 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2621
What does P2621 mean?
P2621 means "Throttle Position Output Circuit Low". P2621 flags the throttle position output line as shorted to ground or reading below its permitted voltage band. It is a generic code, so it means the same on every make.
Is it safe to drive with P2621?
P2621 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2621 fail an emissions test?
Yes, it can. P2621 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2621 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P2621 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.