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:
  • Lack of power
  • Faulty O2 Sensor
  • Poor acceleration
  • The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.
Place of U0120 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.
  • Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.

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 :

If you find a related TSB, the information will often help in diagnosing the code in question as TSBs are crested from many thousands of repairs. 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. 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 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.

Diagnostic Trouble Code look-up and check engine light code viewer.

Copyright 2020 - https://diagnosticTrouble.com

Small Logo