P1121 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

The Powertrain Control Module (PCM) uses the information from the Throttle Position Sensor (TPS) to calculate throttle openings to match engine speed and load.

Causes

Common causes for this code include:

• Faulty electric throttle control actuator
• Throttle Position Sensor (TPS) that is out of adjustment or faulty
• Vacuum leaks in the intake manifold or related vacuum hoses
• Electrical issues such as loose, damaged, or corroded wires/connectors
• ECM/PCM that is faulty

Symptoms

The symptoms of a P1121 code are:

• Illuminated Check Engine Light
• Idle speed is unstable or vehicle idles erratically
• Engine may stall
• Gear selection issues
• Reduced fuel economy
• Acceleration may be delayed
• May enter limp mode

Diagnosis

To diagnose a P1121 DTC code, a technician would:

1. Scan for codes in the ECM and look at the freeze frame data for failure.
2. Visually inspect the electrical connector at the electric throttle control actuator for any damage or corrosion.
3. Inspect all related vacuum hoses and intake manifold gaskets for leaks.
4. Check the Throttle Position Sensor (TPS) adjustment.
5. With a scan tool, check the live data stream from the TPS to ensure it is within specification.
6. If everything looks good so far, then the next step would be to check for voltage and ground at the electric throttle control actuator connector.
7. If all checks out okay, then the last step would be to test or replace the ECM/PCM.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1121 code:

• Not thoroughly inspecting all the wiring and connectors for damage or loose connections
• Not properly checking the TPS adjustment
• Not paying attention to other codes that may be present along with a P1121 code
• Replacing parts without first checking for voltage and ground at the electric throttle control actuator connector
• Failing to check for other codes that may be stored in the ECM/PCM

How serious is this?

A P1121 code is a serious code because it can cause the engine to stall and may prevent the vehicle from starting. If the engine stalls while driving, it could cause an accident.

What repairs can fix the code?

The following are solutions that may fix this problem:

• Broken or faulty wirings must be repaired or replaced as needed
• Damaged or faulty vacuum hoses must be replaced
• Intake manifold gaskets may need to be replaced
• The Throttle Position Sensor (TPS) may need to be adjusted or replaced
• The electric throttle control actuator may need to be replaced
• The ECM/PCM may need to be tested or replaced

Related codes

A P1121 is related to and may be accompanied by the following codes:

P1122 – Electric Throttle Control Actuator Position Sensor Circuit Low Input

P1123 – Electric Throttle Control Actuator Position Sensor Circuit High Input

P1124 – Electric Throttle Control Actuator Position Sensor Circuit Intermittent/Erratic/Incorrect Signal

Conclusion

In conclusion, the P1121 code is a diagnostic trouble code that refers to a problem with the electric throttle control actuator. This code is set when the Powertrain Control Module detects an abnormal signal from the electric throttle control actuator or if there is a problem with how it is operating. The most common cause for this code is a faulty electric throttle control actuator, but it can also be caused by other issues such as a Throttle Position Sensor that is out of adjustment or faulty, vacuum leaks in the intake manifold or related vacuum hoses, electrical issues such as loose, damaged, or corroded wires/connectors, or an ECM/PCM that is faulty.