P0220

What Does Code P0220 Mean?

DTC P0220 signifies a detected electrical circuit malfunction within the “Sensor/Switch B” portion of the Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) sensor system. In modern vehicles equipped with electronic throttle control (ETC) or “drive-by-wire” systems, the Powertrain Control Module (PCM), also known as the Engine Control Module (ECM), relies on these sensors to accurately determine the driver’s throttle input and the actual throttle plate position. For safety and redundancy, these systems typically employ multiple sensor elements (often designated A, B, C) within a single physical sensor unit. These redundant sensors often provide opposing voltage ramps (e.g., sensor A voltage increases as throttle opens, while sensor B voltage decreases) or distinct, offset voltage ranges, allowing the PCM to cross-check their rationality.

When the PCM detects P0220, it indicates that the voltage signal from Sensor/Switch B is either out of its expected operational range (too high or too low), exhibits intermittent behavior, or shows a significant, unplausible discrepancy when compared to the signal from Sensor/Switch A (or other redundant sensors if present). This circuit malfunction directly impacts the PCM’s ability to precisely control engine speed and power output, often triggering a “limp-home” mode to prevent potential safety issues or engine damage.

Common Symptoms

• Malfunction Indicator Lamp (MIL) Illumination: The “Check Engine” light will be illuminated.
• Reduced Engine Power (Limp Mode): The vehicle’s speed and power may be severely restricted to a predetermined safe operating mode.
• Erratic or No Throttle Response: The engine may not respond to accelerator pedal inputs, or the response may be inconsistent.
• Engine Hesitation or Stalling: The engine might stumble or die, especially when attempting to accelerate.
• Unintended Acceleration or Deceleration: Although less common, a faulty sensor signal can potentially cause the throttle to open or close without driver input.
• Inoperable Cruise Control: The cruise control system will typically be disabled due to the critical nature of the throttle position data.

What Causes the Code P0220?

• Faulty Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) Sensor: Internal electrical failure, often due to wear on the resistive track or faulty internal components, causing erratic or out-of-range signals from the “B” circuit.
• Damaged Wiring Harness: Open circuits (broken wires), short circuits to voltage or ground, or excessive resistance within the wiring connected to the TPS/APP Sensor B circuit.
• Corroded or Loose Connectors: Poor electrical contact at the TPS/APP sensor connector or the PCM connector due to corrosion, bent pins, or insufficient terminal tension.
• Faulty Electronic Throttle Body (ETB) Assembly: If the TPS is an integrated, non-serviceable component of the ETB, an internal failure of the sensor requires replacement of the entire throttle body.
• Ground Circuit Issues: A poor or intermittent ground connection for the TPS/APP sensor B circuit.
• Faulty Powertrain Control Module (PCM): While less common, an internal PCM fault affecting the sensor reference voltage, ground, or signal processing for the sensor B circuit can trigger this code.

How to Diagnose and Troubleshoot

Diagnosing P0220 requires a methodical approach, utilizing a professional OBD-II scan tool and a digital multimeter (DMM).

1. Initial Visual Inspection:
   • Begin by visually inspecting the wiring harness and electrical connectors for the Throttle Position Sensor (located on the throttle body) and the Accelerator Pedal Position sensor (located at the accelerator pedal assembly).
   • Look for signs of chafing, fraying, cuts, or pinched wires. Check for bent, corroded, or loose pins within the connectors. Ensure connectors are fully seated.
   • Trace the wiring as far as possible towards the PCM, checking for any signs of damage.
2. OBD-II Scan Tool Live Data Analysis:
   • Connect a professional scan tool and access the live data stream with the ignition on, engine off (KOEO).
   • Monitor the voltage readings for both TPS Sensor A and Sensor B (or APP Sensor A and Sensor B, depending on the specific vehicle and sensor configuration).
   • Slowly depress the accelerator pedal from 0% to 100% and observe the voltage sweep for both sensors. They should exhibit smooth, consistent voltage changes without sudden drops, spikes, or flat spots.
   • Pay close attention to Sensor B’s voltage. It should typically have an opposing ramp or a distinct offset voltage range compared to Sensor A. For instance, if Sensor A ranges from 0.5V to 4.5V, Sensor B might range from 4.5V to 0.5V or 1.0V to 4.0V, but the crucial aspect is its rationality compared to Sensor A. The PCM typically expects a specific correlation between the two.
   • If Sensor B’s voltage is stuck high, stuck low, erratic, or shows an illogical relationship with Sensor A, it points to a problem in Sensor B’s circuit.
3. Digital Multimeter (DMM) Testing:
   • Verify Reference Voltage: With the sensor connector disconnected (KOEO), use the DMM to check for a stable 5-volt reference voltage (Vref) at the appropriate pin for Sensor B. Also, verify a good ground signal at the corresponding ground pin.
   • Test Signal Wire Continuity and Shorts: Disconnect both the sensor connector and the PCM connector. Use the DMM to check for continuity of the signal wire for Sensor B between the sensor connector and the PCM connector. There should be less than 5 ohms of resistance. Also, check for shorts to ground and shorts to power on the signal wire.
   • Test Sensor Output (Back-Probing): Reconnect the sensor. With KOEO, carefully back-probe the signal wire for Sensor B at the sensor connector (or a convenient point along the harness) while slowly manipulating the throttle plate (for TPS) or accelerator pedal (for APP). Monitor the voltage sweep on the DMM. Look for a smooth, linear change across the entire range of motion. An internal sensor fault will often manifest as flat spots, sudden voltage drops, or no voltage change at all.
   • Wiggle Test: While monitoring live data or DMM voltage readings, gently wiggle the wiring harness and connectors for both the sensor and the PCM. Watch for any intermittent changes in voltage, which would indicate a loose connection or damaged wiring.
4. PCM Isolation: If all sensor and wiring checks confirm integrity, and the fault persists, only then consider a potential PCM internal failure. This is a rare occurrence.

Recommended Repairs and Solutions

• Repair or Replace Damaged Wiring/Connectors: If the diagnostic process identifies damaged, chafed, or corroded wiring or connectors, the affected section must be professionally repaired or replaced. Ensure proper crimping and insulation for durable repairs.
• Replace the Faulty TPS or APP Sensor: If DMM tests or live data analysis indicate an internal failure of the Throttle Position Sensor or Accelerator Pedal Position sensor (Sensor B circuit), the component must be replaced. It’s crucial to identify if the TPS is a separate, serviceable component or integrated into the electronic throttle body. If integrated, the entire throttle body assembly will need replacement.
• Throttle Body Cleaning (If Applicable): While not a direct fix for P0220, a dirty throttle body can sometimes affect the smooth operation of the throttle plate, which indirectly impacts TPS readings. If the throttle body is being serviced or replaced due to an integrated TPS, a thorough cleaning is recommended.
• Perform Throttle Body Relearn Procedure: After replacing the APP sensor or, more commonly, the electronic throttle body, many vehicles require a “throttle body relearn” or “idle relearn” procedure using a capable scan tool. This calibrates the PCM to the new component’s operational parameters. Consult the vehicle’s service manual for the specific procedure.
• PCM Replacement (Last Resort): If all other components and wiring have been thoroughly tested and confirmed good, and the issue persists, a faulty PCM may be the cause. This should only be considered after exhaustive troubleshooting, as it is an expensive repair and often requires reprogramming.