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U0126 – 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.

Definition

U0126 is an OBD-II Code that refers to Lost Communication with Fuel Pump Control Module (FPCM)

Meaning

A U0126 code is a diagnostic trouble code that occurs when the other control modules on the vehicle are not communicating with each other. In this instance the Controller Area Network bus communications, or simply CAN indicates there’s a loss of communication with your steering angle sensor module. 

The steering angle position sensor sends a signal indicating the degree to which the steering wheel and front tires are angled. This data is used by the automobile to assist with complex movements, which are frequently associated with accident prevention.

Causes

Common causes for this code include:

  • Open power or ground to SAS module (most common) 
  • Short to power in either CAN bus circuit 
  • Short to ground in either CAN bus circuit 
  • Open in the CAN bus + circuit 
  • Open in the CAN bus – circuit 
  • Bad Control Module (Rare)

Symptoms

The symptoms of a U0126 code are:

  • Illuminated Check Engine Light 
  • Steering wheel performance issues
  • ABS light is Illuminated 
  • TRAC indicator light is Illuminated 
  • ESP/ESC light is Illuminated

Diagnosis

To diagnose a U0126 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect all wiring for damage, chafing, shorts, etc. 
  3. Check power and ground at the SAS module. 
  4. Measure voltage and resistance on both CAN bus circuits.
  5. Test the Control Module.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a U0126 code:

  • Not thoroughly inspecting all the wiring and connectors.
  • Not checking the power and ground at the SAS module.
  • Not checking voltage and resistance on both CAN bus circuits.
  • Testing the Control Module without first clearing the codes.

How serious is this?

A U0126 code in most cases can be serious because of its effects on the steering wheel, ABS, and battery.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Repair or replace any faulty parts such as wiring, connectors, or control modules
  • Check all the fuses and replace any that are blown
  • Replace or repair your vehicle’s battery
  • Replace the SAS module
  • Reset the ECM.

Related codes

A U0126 is related to and may be accompanied by the following codes:

B0085 – Lost Communication with Steering Angle Sensor Module

C0065 – Failed or Incorrectly Installed Control Module.

Conclusion

In conclusion, the U0126 code is a diagnostic trouble code that refers to a problem with the communication between various control modules on the vehicle. The most common causes of this code are an open or short in the power or ground wiring, a bad control module, or a loss of communication on the CAN bus. The symptoms of this code can include illuminated warning lights, steering wheel performance issues, and ABS light illumination. The best way to diagnose and repair this code is to thoroughly inspect all wiring and connectors, check for power and ground at the SAS module, and measure voltage and resistance on both CAN bus circuits.