Dear Tom and Ray: The dashboard of our 2004 Honda lit up like a Christmas tree. We had the car towed to our local Honda dealer. When we were presented with the repair bill, we were dismayed to see that we had been charged $80 three times for “diagnostics.” The service manager explained that they had to connect the car three different times to the diagnostic computer to read the OBD codes. This nasty experience has prompted a couple of questions: (1) Why would they have to connect the computer to the car multiple times? Can't they get all the error codes at once when they first download them? (2) This is a more general question, but why should the customer be charged for the tools the mechanic uses to accomplish his job? After all, don't mechanics need the OBD codes anyway in order to work on today's sophisticated cars? If the mechanic has to use his 5/8 socket wrench to do his job, why should the customer be charged extra for that? It seems to me the diagnostic machine is the same thing. -- Randy

RAY: It certainly seems like a questionable charge, doesn't it? But in fact, there are times when you need to scan a car more than once.

TOM: The codes don't always tell you exactly what to replace; they just indicate a failure of some sort. So if the code says you have an evaporative emissions system failure, you wouldn't start by replacing the whole system; you'd start by replacing the one valve or hose that fails most commonly.

RAY: Then you'd test-drive the car to see if the check-engine light comes on again. If it stays off, you know you've fixed the problem. But if it comes on again, you have to scan the car again for your next clue.

TOM: And whether you know it or not, you DO pay for the mechanic's equipment. If a shop buys an expensive diagnostic machine --whether it's a scanner or a tire balancer -- it charges its customers something every time it's used, to pay for it over time.

RAY: And all businesses charge for their equipment, whether it's separated out in your bill or embedded in the cost of the work. When you go to the hospital, you might pay $1,500 for a night in a hospital bed -- not because the bed is particularly comfortable, but because you're paying for the staff that wakes you up every half-hour and the equipment they stick in you once you're awake.

TOM: And on top of that, if they use a particularly expensive piece of equipment, like an MRI, you get charged for that as well. And it may well be worth it. It may save you several days in the hospital if they can quickly pinpoint your problem.

RAY: The same is true for onboard automotive diagnostics. With the computerized OBD scanner, you get a more accurate diagnosis more quickly, and you save the hours of labor that -- in the old days -- the mechanic would have spent testing each sensor and system individually.

TOM: So we think the dealer has a right to charge you three times if it had to scan your car three times. But we'd never do that.

RAY: No. We'd charge you once for a scan, and then just add the labor time it took to do the follow-up scans.

TOM: The scan tool is a very simple device that plugs in under the dashboard. So there's very little labor involved in hooking it up. It usually takes only a few minutes to plug it in and interpret the results.

RAY: I'll bet if you talk to the service manager, he might be open to giving you a break on your bill. Suggest that you pay for half an hour of labor time instead of the two additional scan charges. And suggest that they may want to make that company policy.