U0004 Reliant Regal Diagnostic Trouble Code

U0004 Reliant Regal code definition:
U0004 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Reliant Regal.

U0004 Reliant Regal is described as Fuel Rail Pressure Sensor Circuit Malfunction. This code is strictly about the incoming signal from the FRP (fuel rail pressure) sensor falling below the calibrated limit for a certain period of time. So if the problem persists despite of your diagnosis, then you should never hesitate to take your vehicle to your dealer or to a qualified mechanic.

Symptoms

Symptoms of a U0004 Reliant Regal diagnostic trouble code may include:
  • Excessive exhaust leak
  • Hesitation upon acceleration
  • Malfunction Indicator Lamp (MIL) illuminated
  • Rich or lean exhaust
Place of U0004 in engine

Possible Causes :

  • Faulty IMRC actuator relay (if equipped)
  • A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.

Common Misdiagnoses

  1. Crankshaft Position Sensor Circuit Performance Problem
  2. TP Sensor Learn Not Complete Problem
  3. Low Coolant Circuit Problem
  4. Cruise Control System - Vehicle Accel Too High Problem
  5. Kick-Down Switch Failed Short Problem

Repair Processes :

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. With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground.

Process Tips

Diagnostic trouble code U0004 Reliant Regal 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 U0004 Reliant Regal.

Fortunately, U0004 Reliant Regal is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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