Q: I recently had my car repaired at a dealership. A service manager said it would take about an hour and a half, another service manager guessed two hours. After the job was started, I received a call saying the job would take 5½ hours. I know repair costs are set by a flat-rate schedule, but is there any way a customer can find out what the rate would be for a specific job? Or are we just at the mercy of the service department?

A: This is an excellent question. First off, if you've signed a work order with a specific estimate, the service agency must get your approval for any significant additional cost or work. The dealership did so in this case. Perhaps they found more damage or additional problems as the work progressed — not an uncommon situation.

The flat-rate service estimate is based on the repair task taking a specific amount of time to perform, as determined by the carmaker or service industry. In effect, this is a fixed price repair, meaning the agency and technician will be paid a fixed amount to do the work. If the tech can do the work in less than the allotted flat-rate time, he makes the same amount of money in a shorter period of time, effectively a higher hourly rate.

My only concern in your case is whether the additional time required was for the exact same repair that was originally estimated at 1 ½ to two hours. If so, you'd have a basis for complaint. But if the additional time was required for additional work, you would have had two choices: accept the additional cost or decline the repair.

Flat-rate repair times are available to consumers. You can ask the service agency what the flat rate is for a specific repair, check your local library for a current flat-rate manual or look up this information online from a number of sources. Some of these offer a free trial period, while others require a subscription. Consider this effort to be your due diligence to protect yourself from being overcharged.

Q: My 2003 Subaru Forester's check-engine light just came on at 189,000 miles. The oil and radiator checked out OK. Is it necessary to pay for a full diagnostic, or can I just keep holding my breath? The repairman said at least 90 percent of the time it isn't serious. Last year I put in $3,500 to stop engine oil leaks and eliminate noise from some part under the hood. They did the timing belt, etc., at same time.

A: Unless the check-engine light is flashing, the issue is not catastrophic. But until you find out which fault triggered the light, you, me and your service technician can't be sure that the issue isn't serious.

Since 1996 every passenger car sold in the United States is equipped with an OBDII (on-board diagnostic system, version II) that features self-diagnostic information that can identify more than 400 specific fault codes. So why "hold your breath"? As I have shared in this column a number of times before, many auto parts stores will "pull fault codes" from your car's diagnostic link at no cost to you. Of course, service agencies and dealerships do the same thing as a professional service that in some cases provides more precise, in-depth diagnostic information.

Since you've already spent a significant amount of money on recent repairs and maintenance, you should absolutely have a parts store, service agency or dealership plug a scan tool into the diagnostic link to identify any DTC (defect trouble codes) stored in the vehicle's computer systems. At least you'll know if it's serious and can then make a rational decision on whether to fix the problem.