Common Causes of a Check Engine Light

Diagnosing Your Check Engine Light

Nothing causes more unnecessary stress to a car owner than seeing the little orange check engine light illuminate. For those not fluent in vehicle maintenance, it seems as though this can be due to a million issues in today’s complex vehicles. Luckily every car is made up of the same moving parts, even if there are a lot), and it helps to know that they all function in roughly the same manner.

A typical check engine light diagnosis includes a conversation to learn as much about the concern from the customer as possible, a test drive to observe data from the car’s computer and to attempt to duplicate the fault. Once we have codes and have duplicated the concern, each manufacturer provides a procedure to troubleshoot each problem. At Cary Car Care, we research your information, follow the procedure and then talk with you about the diagnosis and the estimate to repair.

A typical diagnosis costs $53-$110 (roughly one half to a full hour of time). Some problems require more test time or are intermittent (and difficult to duplicate). The charge to diagnose is directly related to the time it takes to find the problem. We try to stay in constant contact with you to make sure your expectations align with reality, and as always remain as transparent as possible to the consumer. And just as a reminder, our technicians do NOT work on commission, so you can always expect an honest diagnosis here at Cary Car Care!

Common Causes of a Check Engine Light

Failed Oxygen Sensor
Oxygen sensors are the most common sensors to fail in vehicles. This little guys’ job is to tell the vehicles computer how much air and fuel to mix for the engine to run smoothly. All obd2 cars have multiple o2 sensors (at roughly $300 each). Mass air flow sensor codes and o2 sensor codes can be the result of vacuum leaks (intake gaskets, pcv systems, vacuum lines or mass air flow tubes leaking air into the engine bypassing the MAF/ mass air flow sensor).

  • Signs- Rough Idle, terrible fuel efficiency, stuttering during acceleration
  • Diagnosis – Have Diagnostics Checked at CCC
  • Cost to repair – Typically around $300 each

Failed Catalytic Converter
Your Catalytic Converter is responsible for turning toxic combustion gases from the motor into mostly harmless exhaust. Most modern cars have at least 2 catalytic converters, sometimes costing upwards of $2,000 each.

  • Signs – Rotten Egg Smell (sign that CC is not converting Hydrogen Sulfide into sulfur dioxide properly)
  • Diagnosis – Have Diagnostics Checked at CCC
  • Cost to repair – $600 – $1200

Bad Ignition, Spark Plugs
Normally the cause of a failed Catalytic Converter, the ignition system provides the spark necessary to ignite the fuel in your engines cylinders. When the fuel is not sufficiently ignited it passes through the exhaust system into the Catalytic Converter.

  • Signs – Car will start and then die, or not start at all. Hesitation under acceleration
  • Diagnosis – Visual inspection of coil and wires, Have diagnostics checked at CCC
  • Cost to repair – $200-$400

Mass Air Flow Sensor Failure
The Mass Air Flow Sensor (MAF) measures the amount of air passing through the intake, then helps the computer determine the optimum mix of fuel and air for the engine to run smoothly.

  • Symptoms – Erratic Idle, Bumpy Acceleration, Poor Throttle Response
  • Diagnosis – Have Diagnostics Checked at CCC
  • Cost to repair – $400 – $600

Worn Gas Cap
Your issue may be as replacing a worn gas cap! The air allowed into your vehicles fuel system from a loose gas cap can interrupt the fuel supply enough to trigger a response from the monitor. Usually the seal around the cap weakens over time; This requires the cap to be replaced. While there are many aftermarket options, we prefer original equipment caps since the evap system is so sensitive (the evap system is responsible for keeping raw fuel from evaporating into the atmosphere).

  • Signs – Fuel Smell near gas door
  • Diagnosis – See if cap is loose or will tighten properly
  • Cost to repair –$25-35 if you must replace

As always, here at Cary Car Care we are happy to help you diagnose your car’s Check Engine Light issues. Remember that a responsible and dedicated maintenance schedule can play a major role in never seeing your car’s check engine light at all, and we are happy to help with all of your maintenance needs!

Remember – It must be right, or we’ll make it right!

Written by Cary Car Care