Computer controlled fuel injection. When it's working right things are good, lots of power, good mileage, low maintenance, very clean emissions. When it's not working right you need someone with the experience to properly diagnose the problem and decide the correct repair. Someone that has been around long enough to see engine performance repairs go from points and carburetors to the complex fuel and ignition systems of today. That's what you get when you bring your vehicle to Castner's, access to ASE certified master technicians with enhanced state of California smog technician licenses and a combined experience of over 50 years with engine performance diagnoses and repairs.
Here we see a Snap-on MT2500 scanner hooked to the computer of this vehicle. As computers control more and more systems a good scanner is essential. It's our "X-Ray" in to the computer. Will it tell you exactly what is wrong? No, in fact it's basically row after row of data. Like O2V = .456 and CTSV = 3.7 and VS = 12. It's the technicians job to interpret the data and decide on a course of action.
We get many vehicles from other shops that have "done what the scanner said" and the problem persists. For example: the computer may store a trouble code for "Oxygen sensor voltage high" but changing the sensor won't change the sensor output, it will still be high. You have got to find out why the computer can not control the fuel mixture. Only after repairing this will the oxygen sensor output be correct.