U2181 Honda SM-X Diagnostic Trouble Code

U2181 Honda SM-X code definition:
U2181 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Honda SM-X.

U2181 Honda SM-X is defined as Ignition Coil B Primary/Secondary Circuit Malfunction.This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II tool, or vehicles made since 1996 up to present. Any code that causes the vehicle's engine to die while running should be fixed as soon as possible, as it can be dangerous for both the vehicle and the passengers of the vehicle.

Symptoms

Symptoms of a U2181 Honda SM-X diagnostic trouble code may include:
  • Excessive exhaust leak
  • Hesitation upon acceleration
  • Malfunction Indicator Lamp (MIL) illuminated
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
Place of U2181 in engine

Possible Causes :

  • An air leak forward of the DPF will change the sensor readings resulting in the code
  • Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks.
  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.

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 :

It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem. 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. 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.

Process Tips

Diagnostic trouble code U2181 Honda SM-X 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 U2181 Honda SM-X.

Fortunately, U2181 Honda SM-X is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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