P0124 Code: Throttle/Pedal Position Sensor/Switch A Circuit Intermittent

What the P0124 code means

The throttle position sensor (TPS) A sits on the throttle body, at the end of the throttle shaft. The computer relies on it because it manages acceleration enrichment, fuel cutoff on deceleration, idle speed and automatic transmission shifts.

The computer detected that the TPS signal disappears or jumps for a moment and then comes back. Brief dropouts like that are almost never the sensor. They are the typical signature of a loose connection in the connector, or of a wire broken inside its insulation that opens the circuit with vibration or heat.

Remember that the P0124 code points to the circuit where the computer saw the anomaly, not necessarily the failed part. Check the wiring before you replace the sensor, and test the TPS step by step as described below.

P0124 code symptoms

• Check engine light on steadily.
• Jerking or a dead spot when you press the accelerator.
• Rough or high idle.
• Limp mode with limited power on electronic throttles.
• Harsh shifts in the automatic transmission.
• The symptoms come and go, often with bumps in the road, rain or when the engine warms up.
• Companion codes for the same sensor may appear (low signal, high signal or intermittent).

Likely causes of the P0124 code

1. Loose connection in the connector: loose, backed-out or corroded pins.
2. Wire broken inside its insulation, which opens the circuit with vibration.
3. Harness rubbing against moving or hot parts.
4. Loose shared ground that affects several sensors at once.
5. Sensor with an intermittent internal fault, which is less common than the causes above.
6. Complementary check: carbon buildup in the throttle body keeps the throttle from closing completely and changes the reading at idle.

How to diagnose the P0124 code step by step

1. Read the sensor live data and compare it with what is expected. The TPS signal should rise steadily as you open the throttle, with no jumps, and on electronic throttles it should agree with track B and with the pedal.
2. Inspect the connector. Unplug it, look for green, backed-out or oily pins, and plug it back in firmly.
3. Check the supply. There should be 4.8 to 5.1 V on the reference with the key on.
4. Check the ground. The voltage drop between the sensor ground and the battery negative should be under 0.1 V.
5. Measure the signal with the connector plugged in using back-probes. It should change smoothly with the condition (position or pressure).
6. Do the wiggle test with the engine running. Move the harness and the connector while you watch the live data, because a jump shows you where the fault is.
7. Check the continuity of each wire between the sensor connector and the computer connector with the key off.

How to fix the P0124 code

• Repair or replace the connector terminals that do not grip properly.
• Replace the damaged section of wire and protect it from rubbing.
• Only if the fault continues with perfect wiring, replace the sensor.
• Use a quality original or equivalent sensor, because cheap generic ones often have different response curves.
• Clear the codes, drive one full cycle and check in live data that the reading makes sense.

Technical reference data

• 5 V supply, ground and signal.
• Throttle closed: roughly 0.4 to 0.9 V.
• Throttle wide open: 4.0 to 4.8 V.
• On electronic systems, track B usually runs in the opposite direction or with a different slope.
• Values are approximate, so check the manufacturer data for your engine.

Brand-specific notes

When you see a P0124 code on an electronic throttle, the TPS usually cannot be bought on its own. The whole throttle body is replaced, and afterward the throttle position relearn is done.

P0124 on Toyota

On Toyota electronic throttles the TPS is not sold separately. You replace the complete throttle body and then do the throttle position relearn.

P0124 on Nissan

On Nissan electronic throttles the TPS is not sold separately. You replace the complete throttle body and then do the throttle position relearn.

P0124 on Volkswagen

On Volkswagen electronic throttles the TPS is not sold separately. You replace the complete throttle body and then do the throttle position relearn.

P0124 on GM

On GM electronic throttles the TPS is not sold separately. You replace the complete throttle body and then do the throttle position relearn.

Frequently asked questions about P0124