On Board Diagnostics for Your Engine

Sensors throughout a vehicle send readings to the Engine Control Module. These readings help the computer make adjustments in various vehicle systems to allow for constantly changing driving conditions and even to compensate for minor problems. However, if the computer encounters a situation it can’t adjust for, it turns on the Check Engine light. (The Check Engine light is called the “service engine soon” light on some vehicles.)

These options are often not the money-savers they seem for Tucson vehicle owners. They can end up costing the vehicle owner extra in unnecessary repairs and engine damage.

For example, the trouble code P0133 reads “Bank 1 sensor 1 circuit slow response.” Translated, that means the front oxygen sensor shows a slow response time in changing the mix of air to fuel. The seemingly obvious conclusion is that the sensor needs to be replaced. The vehicle owner purchases a sensor, installs it and happily goes on his way.

However, read the trouble again: a slow response time in changing the mix of air to fuel. Nowhere does this indicate that the sensor is bad. There are a lot of parts involved in changing the air-fuel mix, any of which could be causing a slow reaction time. Those include a bad or contaminated airflow sensor, an exhaust leak, a problem in the electrical system or a leak in the intake manifold. The sensor is merely relaying that the response time is slow; it doesn’t indicate where the trouble is.

So the vehicle ends up with an oxygen sensor it did not need, and the delay in repairing the actual problem may have led to further damage to the engine. Both are added costs for the vehicle owner.

On-board diagnostics, then, are a tool to help diagnose what is wrong with a vehicle. They cannot specify what part needs to be fixed or replaced, and they cannot replace a well-trained and well-equipped service technician.