U0251 Daihatsu D-Compact Diagnostic Trouble Code

U0251 Daihatsu D-Compact code definition:
U0251 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Daihatsu D-Compact.

U0251 Daihatsu D-Compact is described as Intake Air Temperature (IAT) Circuit Malfunction. It's actually a general trouble code for a problem on IAT electrical circuit sensor, as it sends incorrect voltage input signals to the PCM. This is because the barometric pressure sensor is part of the MAF sensor. Sometimes, the MAF's sensing wire can accumulate and get covered with dirt, dust and/or oil residue, which can also lead to the error code.

Symptoms

Symptoms of a U0251 Daihatsu D-Compact diagnostic trouble code may include:
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
  • Faulty PCM
  • 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 U0251 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.
  • An air leak forward of the DPF will change the sensor readings resulting in the code

Common Misdiagnoses

  1. Vehicle Speed Output Circuit Problem
  2. Cruise Control Servo Indicates Low Problem
  3. A/C System High Pressure High Temperature Problem
  4. PCM Stack Overrun Problem
  5. Transmission Control Module Reprogrammable Memory Problem

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio. If the scan tool has that capability, and the scan tool can operate the IMRC valves, then the problem is either resolved and a simple code clearing is all that's left or a new PCM would be called for.

Process Tips

Diagnostic trouble code U0251 Daihatsu D-Compact 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 U0251 Daihatsu D-Compact.

Fortunately, U0251 Daihatsu D-Compact is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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