What is the P0124 code?
The P0124 trouble code is a generic powertrain code. It indicates that the Powertrain Control Module (PCM) has detected intermittent or erratic operation in the Throttle Position Sensor (TPS) “A” circuit. This code applies to most vehicles built after 1996 (Dodge, Chrysler, Hyundai, Jeep, Mazda, etc.), although specific diagnostic procedures may vary by make and model.
Role of the Throttle Position Sensor (TPS)
The TPS is a potentiometer mounted on the throttle body. It is connected to a 5-volt reference circuit and is mechanically actuated by the throttle shaft. When you press the accelerator, the sensor’s resistance changes, which alters the voltage signal sent to the PCM.
The PCM uses this information to:
- Calculate fuel delivery and ignition timing.
- Monitor intake airflow and Exhaust Gas Recirculation (EGR).
- Determine engine load.
If the PCM receives inconsistent signals over a given period, it will store the P0124 code and may illuminate the Malfunction Indicator Lamp (MIL).
Symptoms of the P0124 Code
A problem with the TPS can seriously affect engine performance. Common symptoms include:
- Hesitation or stumbling during acceleration
- Black smoke from the exhaust (especially on startup)
- Hard starting, particularly when cold
- Reduced power and fuel efficiency
- Appearance of other emission-related codes
Possible Causes of the P0124 Code
- Faulty or misadjusted TPS sensor
- Damaged, corroded, or loose wires/connectors in the “A” circuit
- Sticking or damaged throttle body
- PCM programming issue or failure (less common)
How to Diagnose and Repair the P0124 Code?
1. Check Technical Service Bulletins (TSBs)
Consult your manufacturer’s TSBs. It might be a known issue with a specific correction procedure, which can save you time.
2. Visual Inspection
Carefully inspect the wiring, connectors, and throttle body. Look for signs of wear, corrosion, damage, or carbon buildup that could impede movement.
3. Use an OBD2 Scanner
Connect a scanner to retrieve all codes and freeze frame data. Clear the codes and perform a road test to see if P0124 returns. Monitor the TPS live data stream for erratic values.
4. Electrical Test with a Multimeter (DVOM)
With the ignition on, measure the voltage between the TPS signal and ground. The voltage should increase smoothly and progressively from ~0.5V (throttle closed) to ~4.5V (wide open throttle). A voltage drop or spike indicates a faulty sensor.
5. Replacement and Adjustment
If the TPS is faulty, replace it. On some vehicles, a precise adjustment is required after installation. Refer to the manufacturer’s specifications.
Conclusion
The P0124 code indicates an intermittent problem often related to the TPS sensor or its circuit. Although diagnosis can be complex due to the intermittent nature of the fault, a methodical approach based on inspection, scanning, and electrical testing can identify and resolve the root cause.
Call to Action: Not comfortable with these procedures? Entrust the diagnosis to a qualified mechanic to avoid causing further damage to your vehicle.