U3921 Nardi 750 Diagnostic Trouble Code

U3921 Nardi 750 code definition:
U3921 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Nardi 750.

U3921 Nardi 750 is described as Oxygen Sensor Circuit No Activity Detected Bank 2 Sensor 1. This code appears when the PCM (powertrain control module, also known as ECM or engine control module in other brands) remains at or close the 0.450 set voltage point. If the car doesn't start, they will proceed by testing the voltage at the fuel pump connector and see if the fuel pump relay, fuse, and PCM circuitry should be inspected.

Symptoms

Symptoms of a U3921 Nardi 750 diagnostic trouble code may include:
Place of U3921 in engine

Possible Causes :

  • A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area.
  • Some aftermarket accessories and performance modifications
  • An air leak forward of the DPF will change the sensor readings resulting in the code

Common Misdiagnoses

  1. TP Sensor Learn Not Complete Problem
  2. Low Coolant Circuit Problem
  3. Cruise Control System - Vehicle Accel Too High Problem
  4. TFP Valve Position Switch-Drive Without Drive Ratio Problem
  5. Problem

Repair Processes :

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. Now, clear the codes and test-drive the vehicle to see if the code is reset.

Process Tips

Diagnostic trouble code U3921 Nardi 750 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 U3921 Nardi 750.

Fortunately, U3921 Nardi 750 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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