U0120 GMC Suburban Diagnostic Trouble Code

U0120 GMC Suburban code definition:
U0120 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for GMC Suburban.

U0120 GMC Suburban is defined as Camshaft Position Sensor A Circuit Low. This means the CMP (camshaft position) sensor circuit on engine bank 1 sends an irregular reading. 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 U0120 GMC Suburban 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
  • Hesitation upon acceleration
Place of U0120 in engine

Possible Causes :

  • A plugged converter will cause of host of driveability problems as well as set this code. A severely plugged converter will result in the inability to increase rpm when under load. Look for a code such as P0421 -- catalytic converter efficiency below threshold if the converter indicating a faulty converter.
  • Dirty air cleaner element Damaged DPF
  • Fuel with a large percentage of sulfur will clog the DPF quickly

Common Misdiagnoses

  1. Exhaust Gas Recirculation System Valve 1 Problem
  2. BBV Sensor Circuit Low Voltage Problem
  3. Transmission Engaged At High Throttle Angle Problem
  4. Cruise Inhibit Control Circuit Problem
  5. TFP Valve Position Switch-Drive Without Drive Ratio Problem

Repair Processes :

You might continue by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. 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. Look for damage to the tank indicating impact that may have damaged the fuel pump or sender.

Process Tips

Diagnostic trouble code U0120 GMC Suburban 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 U0120 GMC Suburban.

Fortunately, U0120 GMC Suburban is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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