P0122 — Throttle/pedal position channel A — low input

P0122 indicates low electrical input from throttle/pedal position channel A. The manufacturer's circuit assignment decides whether A belongs to the throttle, pedal or switch; it does not identify a universally replaceable part. Missing reference/ground, wiring and sensing hardware are separate fault paths.

Affected system: Powertrain

Symptoms

• Engine warning and possible reduced torque or throttle response.
• Intermittent acceleration response, jerks or irregular idle, depending on the vehicle.
• On some vehicles only an intermittent stored code remains.

Possible causes

• Channel A signal grounded or open depending on design, corrosion or loose terminal.
• Missing reference supply or incorrect ground, possibly shared with another sensor channel.
• Failed throttle potentiometer, pedal sensor or proven mechanical restriction; contactless sensors are not diagnosed by resistance sweep.

What to check

• 1. Record P0122 details, freeze-frame and companion A/B/reference-voltage faults. Several channels failing together call for a common supply or ground check first.
• 2. Use the VIN wiring map to determine whether channel A is at the throttle, pedal or a switch. The letter alone cannot identify the part.
• 3. Observe A and any redundant position channels with a scan tool during the manufacturer-permitted slow actuation. A stuck-low A with other tracks changing points toward that signal path, not necessarily the entire throttle body.
• 4. Inspect terminals, moisture, harness routing and recent repairs. Repair displaced contacts and repeat the signal observation to confirm the effect.
• 5. Measure reference and ground at the correct pins under OEM test conditions. An absent reference must be traced before sensor replacement.
• 6. Compare A at the component and ECU with an appropriate meter or scope. Valid at the component but low at ECU suggests wiring; low at both with correct supplies warrants component diagnosis.
• 7. For a disconnected conventional potentiometer only, follow the OEM resistance-sweep procedure; dropouts suggest a worn track. Never apply this test to powered or contactless sensors.
• 8. Check mechanical movement only as approved for the installed throttle system; do not force motor-driven plates. Run adaptation only if the service procedure requires it.

Also written as: P0122-00, P012200, PO122 (some scan tools add the fault-type byte, e.g. -00).