U0125 Cord 8 Diagnostic Trouble Code

U0125 Cord 8 code definition:
U0125 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Cord 8.

U0125 Cord 8 is described as Oxygen Sensor Circuit No Activity Detected (Bank 1, Sensor 1). This means there's a problem in the front oxygen sensor on Bank 1, as the O2 sensor is inactive. There are two wires dedicated for each coil; one is battery feed which usually comes from the distribution center, and the other one for the coil driver circuit from the PCM. The PCM grounds or ungrounds the circuit to activate or deactivate the coil.

Symptoms

Symptoms of a U0125 Cord 8 diagnostic trouble code may include:
  • Faulty O2 Sensor
  • Lack of power
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
  • Diminished fuel efficiency
Place of U0125 in engine

Possible Causes :

  • A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
  • Faulty IMRC actuator relay (if equipped)
  • Fuel with a large percentage of sulfur will clog the DPF quickly

Common Misdiagnoses

  1. IC Circuit High Voltage Problem
  2. Control Module Throttle Actuator Position Performance Problem
  3. Air Conditioning (A/C) Clutch Feedback Circuit High Voltage Problem
  4. Cruise Vehicle Speed/Set Speed Difference Too High Problem
  5. PCM Stack Overrun Problem

Repair Processes :

If you find a related TSB, the information will often help in diagnosing the code in question as TSBs are crested from many thousands of repairs. Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. Look at the plug wires to make sure they are not burnt or laying on the exhaust.

Process Tips

Diagnostic trouble code U0125 Cord 8 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before U0125 Cord 8.

Fortunately, U0125 Cord 8 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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