Government regulations in the late 70s and 80s posed a serious problem for auto manufacturers. To meet Federal fuel efficiency regulations, engines had to be tuned to run lean. To meet Federal and California smog regulations, lower compression ratios and retarded ignition timing had to be implemented. These modifications resulted in poor running. Drivers expected their engines to stall when cold and when stopped at a traffic light.
As computer chip miniaturization matured, computerized control of automobile engine functions became possible, leading to our current arrangement. Engine sensors are essential to the efficient operation you expect of your vehicle. They interface with the car’s powertrain control module (PCM), giving it the information it needs to control the engine’s operation. When a sensor fails, it harms emissions, drivability, and performance.
Engineers realized there needed to be a way to analyze malfunctions common to all vehicles. The result is your vehicle’s onboard diagnostic system, OBD ll. Vehicles produced worldwide have a “Check Engine” light to warn drivers there is a bad sensor. Often the car continues to run with a bad sensor, and drivers ignore the warning. This is a false economy, as engine damage may result, and poor fuel economy certainly will.
Since you don’t know why the check engine light is on, you should immediately bring the vehicle to our shop. Here are the most common sensors used and how they work:
Oxygen Sensor
Input from the oxygen sensor to the PCM allows the computer to adjust the fuel/air ratio to maximize performance. The sensor determines how much unreacted oxygen is in the exhaust and sends that information to the PCM. The PCM then uses this information to alter the fuel injector pulses to maintain acceptable emissions and optimum fuel economy. Due to their placement in the exhaust stream, oxygen sensors need frequent replacement.
Coolant Sensor
The PCM uses coolant temperature to know when to run the electric cooling fan. Engine overheating could result from a faulty sensor. If the PCM thinks the engine has not warmed up, there will be poor fuel mileage and increased emissions.
Throttle Position Sensor
The throttle position sensor (TPS) tells the PCM what load you put on the engine. The PCM uses this information to adjust spark timing and fuel mixture. We can find a malfunctioning TPS with our state-of-the-art diagnostic tool, the same equipment the dealer service department uses.
Mass Airflow Sensor
The Mass Airflow (MAF) measures airflow into the engine. The information it sends is used for the PCM to control the air/fuel mixture. When air filter replacement is neglected, we find dirty MAF sensors causing a lean fuel/air mixture, hesitation, and poor performance.
Crankshaft Position Sensor
The PCM finds out about the crankshaft position and engine RPMs through the information the Crankshaft Position Sensor sends. In response to this input, the PCM regulates ignition timing, idle speed, and fuel injection operation.
Vehicle Speed Sensor
The Vehicle Speed Sensor (VSS) tells the PCM vehicle speed. The ABS also uses this input.
Manifold Air Pressure Sensor
The Manifold Air Pressure (MAP) sensor tells the PCM the variance between atmospheric pressure and intake vacuum. The PCM uses this information to regulate engine timing. A malfunctioning MAP could cause fuel mixture and spark timing problems.
Call us or visit our website for an appointment to resolve your check engine light and return your car to peak efficiency.
