Throttle/Pedal Position Sensor/Switch “B” Circuit High

What P0223 means

Drive-by-wire throttle bodies use a single non-contact Hall-effect throttle position sensor that puts out two independent signals: VTA1 (throttle position no. 1, the primary angle the computer actually uses) and VTA2 (throttle position no. 2, a secondary signal that rides deliberately higher than VTA1 so the ECM can cross-check the primary). Both share a 5 V reference (the VC line) and a sensor ground (E2), and both rise from a low closed-throttle voltage toward roughly 5 V as the plate opens. P0223 is the sensor "B" high-input code: on a Toyota 1GR-FE system it sets on one-trip logic when VTA2 reaches about 4.8 V or more while VTA1 sits between 0.2 V and 2.02 V for two continuous seconds. That combination -- VTA2 pinned near the top of its range while VTA1 reports only a small-to-mid throttle opening -- cannot happen if the sensor and wiring are healthy, so the ECM treats it as a fault. This is the direct opposite of P0222 (VTA2 low, 1.75 V or less): both watch the same VTA2 channel, but P0223 trips on over-voltage while P0222 trips on under-voltage. Because it is an electronic-throttle fault, the ECM drops into fail-safe -- it cuts current to the throttle actuator so the return spring holds the plate near a 7 degree opening and manages power through intermittent fuel cut and spark control based on the accelerator pedal angle, letting the vehicle limp along.

Symptoms

• Check-engine light appears immediately -- this monitor commands the MIL on the first trip, not after several drive cycles
• Major loss of power, because the throttle drops into fail-safe and the plate is held near a 7 degree rest angle by its return spring
• Dead, unresponsive throttle -- the engine will not rev cleanly and the pedal feels disconnected from the engine
• Reduced top speed, with the need to feather the accelerator just to keep the vehicle creeping forward
• Rough idle or a tendency to stall, especially if the plate rests too closed or is fouled with carbon

Common causes

• Failed throttle position sensor element inside the throttle-with-motor body assembly -- the VTA2 Hall channel has degraded and outputs a stuck-high reading; most common on higher-mileage vehicles
• Open in the VTA2 signal wire between the throttle body connector and the ECM, which lets the input float up toward the reference voltage
• Open in the E2 sensor-ground circuit -- with no ground return, VTA2 is pulled high toward the 5 V supply
• Short between the VC 5 V reference and the VTA2 signal wire, driving VTA2 straight to full scale
• Corroded, spread, or backed-out terminals at the throttle body connector on the VTA2 or E2 pins, creating a high-resistance or open path
• ECM internal fault (rare) -- a damaged VTA2 input or a failed sensor-ground reference inside the computer

Severity & driving advice

Severity: High — The fault drives the electronic throttle into 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 enters limp-home fail-safe with the throttle held near idle, so it will barely accelerate. Repair before your next real trip.

Diagnostic approach

1. Read both throttle position signals on a scan tool — With a scan tool (Techstream on Toyota) watch Throttle Position No. 1 (VTA1) and No. 2 (VTA2) together while you release and press the pedal. P0223 is confirmed when VTA2 sits high near 4.8-5 V while VTA1 stays low in its 0.2-2.02 V band. If BOTH signals read near 4.5-4.98 V everywhere, suspect an open E2 sensor ground shared by both; if only VTA2 is pinned high, the fault is isolated to the VTA2 signal circuit or the sensor.
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 -- focus on the VTA2 and E2 contacts. The connector lives in a hot underhood spot, so heat-cracked housings and water intrusion are common. Repair any bad terminal before condemning the sensor, and wiggle-test the connector while watching live VTA2 data to catch intermittent spikes.
3. Check the VTA2 signal wire for an open — With both the throttle body connector and the ECM connector unplugged, measure resistance on the VTA2 line from the throttle body pin to the matching ECM pin -- it should read below 1 ohm. A high or infinite reading confirms an open in the VTA2 signal wire, which allows the ECM input to drift up toward the reference voltage and trip the high-input code.
4. Verify the E2 sensor ground is intact — Still with both connectors apart, check continuity of the E2 sensor-ground line from the throttle body pin to the ECM pin; it should be below 1 ohm. An open E2 circuit removes the ground reference and pulls VTA2 (and often VTA1) high, so a bad ground can set P0223 even with a perfectly good sensor. Repair the ground path before replacing parts.
5. Look for a short between VC and VTA2 — With the connectors disconnected, measure resistance between the VC 5 V reference line and the VTA2 signal line -- a healthy pair reads open (very high resistance). A low reading means the two wires are shorted together, which forces VTA2 up to full scale. Inspect for a chafed or pinched harness section where the reference and signal wires run side by side.
6. Confirm the VTA2 output pattern, then replace the throttle body if the wiring is good — On a healthy sensor VTA2 sits around 2.1-3.1 V released and rises toward 4.6-4.98 V at wide-open throttle, always offset above VTA1; its normal window is above 1.75 V and below 4.8 V. If VTA2 reads 4.8 V or more with VTA1 still low, and the VTA2 wire, E2 ground, and VC line all pass, the internal sensor is at fault. Because the sensor is built into the throttle-with-motor body and not sold separately, replace the complete assembly, then perform the throttle initialization/relearn and re-run the confirmation drive.

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