C0091 Chevrolet Cobalt Diagnostic Trouble Code

C0091 Chevrolet Cobalt code definition:
C0091 is a kind of OBD-II Diagnostic C-Chassis Diagnostic Trouble Code for Chevrolet Cobalt.

C0091 Chevrolet Cobalt is a DTC or a diagnostic trouble code. It is a check engine light code which indicates that the catalyst's system efficiency is less than the required threshold. In simple terms, it means that more pollution is added into the air than what was supposed to be because of your car. Other symptoms that may indicate this problem are when the Check Engine Light illuminates and when there is a visible lack of engine power.

Symptoms

Symptoms of a C0091 Chevrolet Cobalt diagnostic trouble code may include:
Place of C0091 in engine

Possible Causes :

  • Fuel with a large percentage of sulfur will clog the DPF quickly
  • The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
  • An air leak forward of the DPF will change the sensor readings resulting in the code

Common Misdiagnoses

  1. Vehicle Speed Output Circuit Problem
  2. Cruise Control Servo Indicates Low Problem
  3. A/C System High Pressure High Temperature Problem
  4. PCM Stack Overrun Problem
  5. Transmission Control Module Reprogrammable Memory Problem

Repair Processes :

Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition. Pack the connector cavity with dielectric silicone compound (same stuff they use for light bulb sockets and spark plug wires) and reassemble.

Process Tips

Diagnostic trouble code C0091 Chevrolet Cobalt 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 C0091 Chevrolet Cobalt.

Fortunately, C0091 Chevrolet Cobalt is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

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