U0121 Engine Error Code

When you check engine light came on code U0121 the reason should be Engine Light ON (or Service Engine Soon Warning Light). However your vehicle's manufacturer may have a different definition for the U0121 OBD-II Diagnostic Network (U) Trouble Code. So you should chech it on your car models.

U0121 Code Symptoms

U0121 OBD2 may also be triggered by faults earlier down the line. For example, a dirty MAF sensor might be causing the car to overcompensate in its fuel-trim adjustments. As a result, oxygen sensors are likely to report fuel mixture problems.

Power Steering Pressure (PSP) Switch Signal Malfunction The PCM counts the number of times vehicle speed transitions from 0 to a calibratable speed. After a calibratable number of speed transitions the PCM expects that the PSP input should have changed. This DTC is set if the transition is not detected. Vehicle towed with engine running Power steering hydraulic concern was repaired but DTC was not erased PSP switch/shorting bar damaged SIG RTN circuit open PSP circuit open or shorted to SIGRTN PCM damaged Check, if possible, if vehicle was towed or power steering service was performed. Observe PSP V PID while checking wires for intermittents.

U0121 OBD-II Diagnostic Network (U) Trouble Code Description U0121 OBD-II Trouble Code Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and comm U0121 Code Review : The reason of U0121 OBD-II Engine Error Code is U0121 Lost Communication With Electronic Brake Control Module.

U0121 Code Dictionary Meaning:

u - Network Code - Problem is climate control system, lighting, airbags, etc. 0 - SAE - Generic 1 - Fuel And Air Metering 2 - Cruise Control Servo Indicates Low 1 - PCM Stack Overrun

How long can you drive with a U0121 code ?

If your vehicle is displaying a U0121 OBD2 error code but is still running and driving normally, it means that the issue might not be immediately critical or causing immediate harm to the vehicle. However, it's important to address the issue as soon as possible for several reasons:

• Potential for Worsening
• Decreased Fuel Efficiency
• Emissions Testing Compliance
• Risk of Further Damage
• Safety Concerns
• Legal Considerations