P1220 – Series Throttle Control System Malfunction

What is the P1220 Code?

P1220 is a generic powertrain diagnostic trouble code that indicates a malfunction in the throttle/pedal position sensor or related circuits. The exact definition varies slightly by vehicle manufacturer:

• In most vehicles, it means "Throttle/Pedal Position Sensor/Switch "B" Circuit"
• In Fiat vehicles, it can indicate "Manifold Absolute Pressure/Barometric Pressure Circuit High Input"
• In Isuzu vehicles, it may mean "Manufacturer Controlled Fuel and Air Metering"

When triggered, it means the engine control module (ECM) has detected an issue with the "B" circuit of the throttle position sensor (TPS) or accelerator pedal position (APP) sensor. These sensors inform the ECM of the throttle and accelerator pedal's positions.

Symptoms of P1220

Common symptoms when P1220 is present include:

• Illuminated check engine light
• Reduced engine power
• Engine entering "limp mode"
• Poor or no response when pressing accelerator
• Unable to rev the engine

Severity and Driving with P1220

The severity depends on the root cause, but in most cases, you should not continue driving if P1220 is triggered. Reduced throttle control is a potential safety issue. It's recommended to have the vehicle towed to a shop for proper diagnosis, as continued driving may cause further damage to the throttle control system.

Common Causes

Potential causes that can trigger the P1220 code include:

• Defective throttle position sensor
• Faulty accelerator pedal position sensor
• Damaged wiring or corroded connectors in the throttle/pedal circuits
• Problems with the throttle body
• Faulty ECM (less common)

Specifically in some Fiat 500 models, corrosion in the accelerator pedal connector plug causing poor electrical contact is a common cause.

Diagnostic Steps

To diagnose the underlying cause of P1220, a mechanic should generally:

1. Scan for all codes, document them, clear codes and see if P1220 returns.

2. Visually inspect wiring, connectors and components for the throttle and pedal sensors, checking for damage, corrosion or loose connections.

3. Test sensor voltages with a multimeter and compare to specifications.

4. If voltages are out of range, disconnect the sensor and test its resistance. Replace if faulty.

5. If sensors are okay, check wiring continuity between sensors and ECM. Repair damaged circuits.

6. If wiring is fine, the throttle body may need cleaning or replacement if sticking.

7. Rarely, a faulty ECM is possible, but should be professionally tested before replacement.

Repair Costs

Repair costs for P1220 depend on the root issue. Some common estimated repair costs are:

• Throttle position sensor: $120-$300 (€100-€250)
• Accelerator pedal sensor: $80-$200 (€70-€170)
• Wiring repairs: $50-$300 (€40-€250) based on extent of damage
• Throttle body cleaning: $75-$150 (€60-€125)
• Throttle body replacement: $300-$750 (€250-€625)
• ECM replacement: $500-$1500 (€425-€1250) (uncommon)

Preventing P1220 Issues

Some preventative measures for P1220 and related throttle problems include:

• Periodically inspecting and cleaning the throttle body if needed (every 30,000-60,000 miles or 50,000-100,000 km)
• Properly installing aftermarket accessories to avoid damaging wiring
• Repairing any water leaks that could cause connector corrosion
• Promptly addressing running issues before sensors or wiring are damaged

Understanding the meaning of the P1220 code and logically diagnosing it can usually identify and fix the root problem. Proactive maintenance helps prevent throttle control system issues from developing in the first place. Always consult professional mechanics for complex repairs.

Frequently Asked Questions about P1220 Trouble Code

What does the P1220 code mean?

The P1220 is a generic powertrain code that indicates a problem with the throttle/pedal position sensor or associated circuits. The exact definition can vary by vehicle manufacturer, but it generally points to an issue with the throttle control system.

What are the common symptoms of P1220?

Common symptoms of P1220 include:

• Check engine light illumination
• Reduced engine power
• Engine going into “limp mode”
• Poor or no response from the accelerator pedal
• Inability to rev the engine

Is it safe to drive with the P1220 code?

No, in most cases you should not continue driving if the P1220 code is triggered. Reduced throttle control can be a safety issue. It’s best to have the vehicle towed to a repair shop for proper diagnosis, as continued driving may cause further damage.

What are the common causes of P1220?

Common causes that can trigger the P1220 code include:

• Faulty throttle position sensor
• Defective accelerator pedal position sensor
• Damaged wiring or corroded connectors in the throttle/pedal circuits
• Issues with the throttle body
• Rarely, a faulty engine control module (ECM)

How do you diagnose the P1220 code?

To diagnose P1220, a technician should:

1. Scan for all codes and document them
2. Visually inspect wiring, connectors, and components
3. Test sensor voltages and compare to specifications
4. Check sensor resistance if voltages are out of range
5. Test wiring continuity between sensors and ECM
6. Inspect throttle body for sticking
7. Rarely, test the ECM if no other issues are found

What are the typical repair costs for P1220?

Repair costs depend on the root cause, but some common estimates are:

• Throttle position sensor replacement: $120-$300
• Accelerator pedal sensor replacement: $80-$200
• Wiring repairs: $50-$300 depending on extent
• Throttle body cleaning: $75-$150
• Throttle body replacement: $300-$750
• ECM replacement: $500-$1500 (uncommon)

Can a bad throttle position sensor cause the P1220 code?

Yes, a faulty throttle position sensor is one of the most common causes of the P1220 code being triggered. The sensor may send incorrect voltage signals to the ECM if it has failed or is out of calibration.

Can a bad accelerator pedal position sensor cause P1220?

Yes, just like the throttle position sensor, a defective accelerator pedal position sensor can also trigger the P1220 code. This sensor tells the ECM the position of the accelerator pedal.

What does “limp mode” mean when P1220 is triggered?

When a vehicle goes into “limp mode” due to the P1220 code, it means the ECM has detected a problem with the throttle control system and has restricted engine power to prevent damage. The vehicle may have greatly reduced acceleration and top speed.

Can a loose gas cap cause the P1220 code?

No, a loose gas cap will not directly trigger the P1220 code, as this code is related to the throttle control system, not the evaporative emission control (EVAP) system that a loose gas cap would affect.

Can low battery voltage cause P1220?

Low battery voltage or a weak battery is unlikely to be the direct cause of P1220. However, low system voltage could potentially cause components like sensors to operate incorrectly, which may indirectly lead to the code being triggered.

Can a dirty throttle body cause the P1220 code?

Yes, a dirty or sticking throttle body can cause the P1220 code. If the throttle plate is gummed up with carbon deposits, it may stick or not open and close properly, which could trigger the code.

How often should the throttle body be cleaned to prevent P1220?

As a preventative measure, the throttle body should be inspected and cleaned if needed around every 30,000 to 60,000 miles (50,000 to 100,000 km). A dirty throttle body can cause issues like rough idle, stalling, and trigger codes like P1220.

Can a bad ECM cause the P1220 code?

While it is possible for a faulty ECM to trigger the P1220 code, it is relatively uncommon. A technician should rule out issues with wiring, connectors, and sensors first before suspecting the ECM.

How do you test the throttle position sensor?

To test a throttle position sensor, a technician will typically:

1. Unplug the sensor and check its resistance with a multimeter
2. Compare the resistance to manufacturer specifications
3. Reconnect the sensor and backprobe the wires
4. Check the reference, ground, and signal voltages
5. Compare voltages to manufacturer specifications
6. Replace the sensor if readings are out of range

How do you test the accelerator pedal position sensor?

Testing the accelerator pedal position sensor is similar to testing the throttle position sensor:

1. Unplug the sensor and check its resistance
2. Compare resistance to specifications
3. Reconnect and backprobe the wires with a multimeter
4. Check reference, ground, and signal voltages
5. Compare voltages to specifications
6. Replace sensor if readings are out of range

Can aftermarket accessories cause P1220?

Aftermarket accessories that are improperly installed and interfere with or damage the wiring for the throttle or accelerator pedal position sensors could potentially trigger the P1220 code. It’s important to ensure accessories are installed correctly.

Can a wiring short cause the P1220 code?

Yes, a short or open circuit in the wiring for the throttle position sensor or accelerator pedal position sensor can trigger the P1220 code. Damaged, corroded, or loose wiring and connectors should be inspected when diagnosing the code.

What is the difference between the throttle position sensor and accelerator pedal position sensor?

The throttle position sensor measures the actual position of the throttle valve in the throttle body, while the accelerator pedal position sensor measures the position of the accelerator pedal that is pressed by the driver. Both send signals to the ECM to control the throttle.

Can P1220 be triggered by issues other than the throttle control system?

While P1220 is specifically related to the throttle control system, it’s possible for issues in other related systems to indirectly cause the code to be triggered. For example, a vacuum leak could cause incorrect readings from sensors. However, the throttle system components should be diagnosed first.