"They charged me 187.00 FOR ABSOLUTELY NOTHING!!!!!" That's a one-star review of a Portland-area repair shop, and it isn't really about $187. Another driver paid more and wrote less: "I paid $200 to be told to get lost."
Neither driver was angry that diagnosis costs money. They were angry they found out at the counter. A diagnostic fee is fair. A surprise one isn't.
Chapter 14 covered a line no repair ad we read used: the warranty law. This second bonus chapter covers a number no repair ad we read included, the diagnostic fee, and why putting it in the ad costs a shop less than explaining it at the counter.
This chapter explains the rules for an educational guide. It isn't legal advice. Check your state's estimate and advertising rules before an ad with a price runs.
48 of 389 Bad Repair Reviews Fight Over the Diagnostic Fee. Most Fees They Name Fall Between $100 and $250.
We read every low-star Google review about a repair job at Portland-area shops and dealers in our sample, 389 in all. Forty-eight of them complain about a diagnostic, inspection or "just to look at it" fee. That's about one in eight, and it sits inside a bigger pattern: 184 of the 389 complain about price in some form.
Thirty-eight of the 48 name an amount. The lowest is $50 and the highest is $500 for an A/C system check, but most fall between $100 and $250.
Read them together and the anger sorts into a few kinds:
- The fee that bought nothing. "187.00 FOR ABSOLUTELY NOTHING."
- The fee for something the driver already knew. "Charged me to tell me a problem that I told them when I dropped it off."
- The fee that showed up after drop-off. "Just to look at the car was $200 so I couldn't back out after dropping my car off."
- The fee before the estimate. "Had to pay $241 just to get an estimate."
Even a four-star reviewer, otherwise happy, expected a $179 computer check to come off the repair bill. "There wasn't" a credit.
Mechanics see the other side. In a trade thread on Reddit, one wrote: "Most mechanics get paid flat rate. If they don't charge diag, repair, etc then they are working for free." The fee pays for real work. The reviews show what happens when the driver hasn't been told what that work is, or what it costs, before the keys change hands.
The praise points the same way. One positive review of a chain store singled out that they "Don't charge you if something's not found."
Not One of the 12 Shop Websites We Checked Posts a Diagnostic Fee. Not One of the 479 Ads Does Either.
We checked the websites of 12 repair shops in the same market. None posts a diagnostic fee amount.
One comes close. It explains how its fee works without saying what it is: "Diagnostic fee applied to repair -- if we do the work, the scan fee rolls into the repair bill." That's the right policy, written in the right place, missing the one number a driver wants.
Two other sites go the opposite way and offer something free: a "FREE Check Engine Light - Scan" coupon on one, a "FREE CHECK ENGINE LIGHT REVIEW" on the other. The second one's terms say what "free" covers: "Offer covers visual inspection only; additional diagnostic testing or teardowns required to identify specific malfunctions are not included." Seven of the 12 sites offer some free inspection by name.
The ads follow the sites. Across 479 readable Search ads from local shops, chains and dealers, not one named a diagnostic fee. The only ads with the word "fee" in them were about financing. Chains advertise the free part instead: "a free courtesy inspection with every visit," "a Free Brake Inspection."
So a driver whose check engine light comes on sees free offers in the ads and finds the fee at the counter. That's exactly where the angry reviews start.
"Free Auto Diagnostics" Gets 2,900 Searches a Month. A Free Code Read at a Parts Store Isn't a Diagnosis.
Drivers know a free option exists. Drivers type "free auto diagnostics" about 2,900 times a month across the US, with or without "near me," and ask "car diagnostic test cost" roughly 4,400 times. Reddit drivers pass the tip along: "If you get your car scanned at a parts store, just take the code and Google it."
A parts store scan reads the code. It doesn't find the cause. A driver on r/Frugal put the difference better than most shops do: "The mechanic is doing much more... than AutoZone, plus you're paying for an expert opinion."
Some drivers price the fee by brand before they pick a shop: "firestone diagnostic fee" draws about 720 US searches a month, "diagnostic fee at dealership" 590 and "midas diagnostic fee" 260. An independent shop that posts its number is in that comparison. One that doesn't, isn't.
That's the case the ad has to make, and it can't make it without the number. "Diagnostics" in a headline says nothing about what the driver pays or what the test does. A fee in the headline, with one line on what it covers, answers both before the driver books.
Matching "free" comes with federal guidance. A "free diagnostic with any repair" offer is free only if the driver books the work, and the FTC's guide wants that catch stated at the start of the offer. The same guide caps how often a shop promotes one service as free in its area: 6 months out of any 12. A check engine "free with repair" ad that runs every month of the year goes against it.
A Price Asset Puts the Diagnostic Fee Right Under the Ad. Google's Rules Say the Page Must Show That Price Too.
Two places in a Search ad can carry the fee.
The ad text. Headlines get 30 characters and descriptions 90. Using $129 as an example (each shop sets its own number):
- "$129 Check Engine Diagnostic" (28 characters)
- "Fee Credited Toward Repair" (26)
- "Our $129 test finds the cause, not just the code, and it's credited if we do the repair." (88)
Those lines go in the check engine light and diagnostic ad groups, the searches from Chapter 2 where a driver already knows something is wrong.
A price asset. Google's price assets show a row of services with prices under the ad. Google's help page says a shop must enter "a minimum of 3 items," recommends "5 or more," and allows "up to 25 characters per header and 25 characters per description." For a repair shop, three diagnostic services is a natural set:
- Check Engine Diagnostic, "Finds the cause, not code"
- A/C Performance Test, "Leak and pressure check"
- Battery & Charging Test, "Battery and alternator"
Google's rules for price assets are strict about two things. The header and description can't carry the price or promotional text, so "Free" and "Sale" stay out. And under its unavailable offers policy, "Products or services should be priced accurately, easily found at the ad's destination, and match with headers and descriptions." If the ad says $129, the landing page says $129, near the booking button, with the same line about the credit.
The phone has to match too. The same reviews complain about prices that changed between the call and the counter: "Was told over the phone that an alignment would be $90, got there and the price was $150." If the ad and the page say $129, whoever answers the phone says $129, and the work order says it again before the car goes into the bay. One number in four places is what keeps the fee from becoming a review.
Michigan Law Puts the Diagnosis Cost in the Written Estimate. A Fee Named in the Ad Heads Off the Fight at the Counter.
Some states already require what this chapter recommends, just later in the process. Michigan's repair law requires a written estimate before work begins, and the cost of diagnosis has to be in it. New Jersey and Connecticut also have rules on how a diagnosis charge is disclosed and agreed to before the work. A shop in those states is already writing the number down. The ad only moves it earlier.
When a written estimate is required differs too. California and Michigan require one before the work. Florida requires one when the repair will cost more than $150, Washington when the estimate is over $100, and New York only when the customer asks. A diagnostic fee in the $100 to $250 range sits close to those lines.
The estimate rules also limit how far the final bill can drift. These are the thresholds for charging more than the estimate without the driver's new consent in a few of the states we checked:
- California, New York, New Jersey, Connecticut. Nothing above the estimate.
- Florida. Up to $10 or 10%, whichever is greater, capped at $50.
- Michigan. Up to 10% or $50, whichever is less.
- Oregon. Up to 10% or $200, whichever is less.
- Washington. Up to 110% of the estimate.
A shop's ad shouldn't promise more than its state allows. "No surprises on your bill" is a strong line in California, New York, New Jersey and Connecticut, where any increase needs the driver's consent anyway. In the other states it's a promise the shop has to keep on purpose.
Rules vary by state and change. Confirm your state's estimate, invoice and advertising rules with the agency that licenses or registers repair shops there.
A fee in the ad, a matching price on the page, and a credit policy written in one plain line are how our Google Ads management team handles the diagnostic ad groups in a repair account.
Next: Google Lets You Bid on "Subaru" and "BMW." Your Ad Still Has to Make Clear You Aren't the Dealer.
Chapter 16, the last bonus, covers the car-make searches from Chapter 4, and how an independent specialist's ad stays clear of looking like the dealer's.
This chapter is part of Google Ads for Auto Repair, a sixteen-chapter guide for independent repair shops in every state.
