I heard you have "The Computer"

Very often we get referrals where the customer has been sent to us because we have the so called “computer” to hook up to a certain vehicle brand. This computer is then said to be capable of providing an instant solution to an ongoing problem. It will, as many a customer has said, “turn out the light”.

In our industry, as vehicle complexity has increased, it has become more important to have a specific diagnostic tool that interfaces with your vehicle’s diagnostic network. While there has been a standard diagnostic interface since the 1996 model year (called OBD II) this standard has limited capabilities.

These standard capabilities are limited to your vehicle’s emission control system. As soon as any other systems are involved in the problem the standard diagnostic interface is no longer useful. This standard interface will be able to talk to at least your engine’s computer control system and maybe your transmission’s computer control system. It provides rudimentary diagnostic information as mandated by the government.

When it comes to something like your anti lock brake system (ABS) there are no standards. Diagnosing the antilock brake system is proprietary. This is where a special interface and software is required. The antilock brake system is not the only one that requires proprietary software. Almost every chassis, body, and entertainment/communication system on your vehicle is computer controlled and networked to each other.

Thankfully your vehicle’s manufacturer has decided to make these special tools available not only to the dealership that sold you your vehicle but also to anyone that wants to pay for them. There are also many professional tools that have varying capabilities to help diagnose various systems. Each and every one of these tools is a significant investment with ongoing costs to keep them up to date.

So yes an independent auto mechanic can have the diagnostic tool to work on your vehicle. Without these special tools the diagnostic process may not even be possible.

The right tool is only part of the equation though. Yes, no matter what you might think or what you might have been told this diagnostic tool or “computer” has yet to know what is wrong with your car.

These tools give your mechanic information he/she needs to fix your car but none as yet just come right out and solve the problem. There are inexpensive tools that simply read fault codes. These codes usually start with a letter followed by a four digit hexadecimal number. The description of these faults can be searched on the internet. Many fault codes will refer to a vehicle part in the description. For example P0135: Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1).

The armchair mechanic seeing “Oxygen Sensor” in the fault code description will go out and buy an oxygen sensor and install it. Sure, provided the part is the correct one for the application and it gets installed in the correct position (many vehicles have four of these sensors) there is a reasonable chance that this problem may be solved. Probably better than 50 percent for that particular code. 50% chance on a non-returnable several hundred dollar part. People do like to gamble I guess.

Your professional mechanic armed with the correct diagnostic tool will approach this problem differently. The code, as presented by the manufacturer’s proprietary diagnostic tool, may contain more information. The oxygen sensor heater circuit fault may be flagged as a short to ground. The complete oxygen sensor circuit will require diagnosis. The problem could be a broken wire or bad connection anywhere in the circuit.

The proper diagnostic tool will allow the mechanic to turn on the oxygen sensor heater circuit at will and measure the voltage and current and resistance. A new oxygen sensor could be a complete waste of money.

Guessed wrong? It’s only money. That special “computer” is only as smart as its operator.