U1955 Mazda Xedos+9 Diagnostic Trouble Code

U1955 Mazda Xedos+9 code definition:
U1955 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Mazda Xedos+9.

U1955 Mazda Xedos+9 is described as Fuel System Too Rich, which basically means bank 1's oxygen sensor has detected a rich condition of fuel. This means there's not enough oxygen in the exhaust from too much fuel being delivered into the air and gas mixture for combusion. 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 U1955 Mazda Xedos+9 diagnostic trouble code may include:
  • If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected
  • Corroded or damaged connector
  • Reduction in engine performance, especially at low RPM levels
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
Place of U1955 in engine

Possible Causes :

  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
  • Fuel with a large percentage of sulfur will clog the DPF quickly

Common Misdiagnoses

  1. Control Module Throttle Actuator Position Performance Problem
  2. Air Conditioning (A/C) Clutch Feedback Circuit High Voltage Problem
  3. Cruise Vehicle Speed/Set Speed Difference Too High Problem
  4. Kick-Down Switch Failed Short Problem
  5. Park/Neutral Postion (PNP) Switch Circuit Engine Torque Signal Circuit Problem

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed. Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications.

Process Tips

Diagnostic trouble code U1955 Mazda Xedos+9 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 U1955 Mazda Xedos+9.

Fortunately, U1955 Mazda Xedos+9 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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