Throttle position sensor 2 input low

What P0222 means

Modern drive-by-wire throttle bodies carry a single non-contact Hall-effect throttle position sensor that outputs two independent signals: VTA1 (throttle position no. 1, the primary angle used for engine calculations) and VTA2 (throttle position no. 2, a secondary signal offset above VTA1 that lets the computer cross-check VTA1). Both signals ride on a shared 5 V reference (the VC line) and a sensor ground (E2), and both climb from a low idle voltage toward roughly 5 V as the plate opens -- but VTA2 sits deliberately higher than VTA1 at any given angle so the two can never legitimately match. P0222 is the sensor "B" low-input code: on a Toyota 1GR-FE system it sets on one-trip logic when VTA2 falls to about 1.75 V or less for two continuous seconds, because in normal operation VTA2 should never drop below that floor even at a closed throttle. The likely causes are a VTA2 signal wire shorted to ground, an open in the shared VC reference (which drags both signals toward zero), or a failed sensor inside the throttle-with-motor body assembly. Because this is an electronic-throttle fault, the ECM enters fail-safe: it cuts current to the throttle actuator so the return spring holds the plate at about a 7 degree opening, then manages power through intermittent fuel cut and spark timing based on the accelerator pedal angle, letting the vehicle limp along at reduced speed.

Symptoms

• Check-engine light comes on right away -- this monitor commands the MIL immediately, not after several trips
• Severe loss of power, since the throttle enters fail-safe and the plate is held near a 7 degree rest angle by its return spring
• Sluggish, unresponsive throttle -- the engine will not rev normally and the pedal feels disconnected
• Reduced top speed and the need to feather the accelerator gently just to keep the vehicle moving
• Rough idle or a tendency to stall if the throttle plate rests too closed or sticks with carbon buildup

Common causes

• Failed throttle position sensor element inside the throttle-with-motor body assembly -- the VTA2 Hall channel has degraded; most common on higher-mileage vehicles
• VTA2 signal wire shorted to ground between the throttle body connector and the ECM, pulling the reading below the 1.75 V floor
• Open in the VC 5 V reference circuit, which collapses both VTA1 and VTA2 toward zero at the same time
• Corroded, spread, or backed-out terminals at the throttle body connector on the VTA2 or VC pins
• Moisture or contamination in the throttle body connector creating a leakage path that drags VTA2 low
• ECM internal fault (rare) -- a damaged VTA2 input or a faulty VC reference driver

Severity & driving advice

Severity: High — The fault forces electronic-throttle fail-safe, holding the plate near a 7 degree opening and sharply cutting power -- unsafe at highway speed.

Can I drive? Do not drive normally. The engine goes into limp-home fail-safe with the throttle held near idle, so it will barely accelerate. Repair before the next real journey.

Diagnostic approach

1. Read both throttle position signals on a scan tool — With a scan tool (Techstream on Toyota) read Throttle Position No. 1 (VTA1) and No. 2 (VTA2) together while releasing and pressing the pedal. If BOTH sit at 0-0.2 V everywhere, the shared VC reference is open. If both read 4.5-4.98 V, the E2 sensor ground is open. If VTA2 reads low (near 0-0.2 V) while VTA1 sits in its fail-safe band, the fault is isolated to the VTA2 circuit or the sensor itself.
2. Inspect the throttle body connector and harness — Unplug the throttle-with-motor body connector and examine the terminals for corrosion, green film, spread or pushed-back pins, and moisture -- especially on the VTA2 and VC contacts. The connector sits in a hot underhood location, so heat-cracked housings and water intrusion are common. Repair any bad terminal before condemning the sensor, and wiggle-test the connector on live data to catch intermittent drop-outs.
3. Measure VTA2 harness continuity and check for a ground short — With both the throttle body connector and the ECM connector disconnected, measure resistance on the VTA2 line from the throttle body pin to the matching ECM pin -- it should read below 1 ohm. Then measure that same VTA2 pin to body ground; a healthy circuit reads 10 kohm or higher, while a reading near zero confirms the VTA2 wire is shorted to ground. Check the VC and E2 lines the same way while you are in there.
4. Verify the ECM supplies the 5 V reference (VC) — With the throttle body connector unplugged and the ignition on, measure voltage from the harness-side VC pin to the sensor ground (E2). It should read roughly 4.5-5.5 V. If it reads 0 V, either the VC wire is open or shorted to ground, or the ECM reference driver has failed -- trace the wire for pinch damage before condemning the ECM, since an open VC drives both VTA1 and VTA2 low.
5. Confirm the VTA2 output pattern against spec — On a good sensor VTA2 sits around 2.1-3.1 V with the pedal released and rises toward 4.6-4.98 V at wide-open throttle, always offset above VTA1 (about 0.5-1.1 V released rising to 3.2-4.8 V open). If VTA2 measures 1.75 V or less at any point, that is out of the normal operating window and confirms the low-input fault rather than a wiring or reference problem.
6. Replace the throttle body assembly and relearn if the circuits are good — If harness continuity, ground isolation, and the 5 V reference all pass, the internal sensor is at fault -- and on modern electronic throttle bodies the sensor is not sold separately, so the whole throttle-with-motor body assembly is replaced. Afterward perform the throttle initialization/relearn (ignition-cycle procedure, then let the engine idle undisturbed) so the ECM relearns the closed-throttle position, then clear codes and re-run the confirmation drive.

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