Likely causes
Pick at least one symptom or code to see likely causes.
How to use the result
- Start at the top cause, but do the cheap checks first: connectors and wiring cost nothing to inspect.
- Test before buying. The sweep test separates a worn sensor from a wiring fault in about 20 minutes.
- Read the code guide for any code you ticked: TPS codes hub.
Causes the checker knows about
What the checker weighs
| Cause | Typical clues |
|---|---|
| Worn or failing TPS | Hesitation, surging, P0121, a dropout in the sweep |
| Wiring or connector | P0122 or P0123, readings that change when you wiggle the harness |
| Electronic throttle body | P2135, reduced power, electronic throttle |
| Accelerator pedal sensor | P2135 with pedal codes, electronic throttle |
| Misadjusted or unseated sensor | Codes or high idle right after a replacement |
| Relearn needed | High or hunting idle after battery or throttle work |
| Vacuum leak or dirty throttle body | Rough or high idle with no TPS codes |
| Engine computer | Only after everything else tests good |
Questions people ask
How does the checker rank causes?
Each symptom and code adds weight to the causes that code references and repair guides associate with it. The weights are rules of thumb, not statistics, so treat the ranking as a starting order for testing.
Why does throttle type matter?
On electronic throttles the sensors are inside the throttle body and a pedal sensor is involved, so throttle body and pedal causes become possible. On cable throttles, adjustment becomes possible on some older sensors.
Can the checker replace a scan tool?
No. Codes and live data are the real evidence. The checker helps you decide what to test first and which guide to read.
Sources
Last reviewed 2026-10-12. General guidance only: specs, procedures and fitment vary by vehicle, so confirm in your service manual and on the listing before you buy or wrench.