A Seattle law firm considering a class action suit against Apple wants iPhone users whose devices have been crippled by "Error 53" to contact their office.

The firm -- Pfau, Cochran, Vertetis, Amala (PCVA) -- said on its website that it is "investigating a potential class action lawsuit against Apple," and asked owners of iPhone 6, 6 Plus and their successors to fill out a form "if you have encountered 'Error 53.'"

Attorneys planning on a class action lawsuit often publicize such pleas to locate affected consumers who can serve as the case's plaintiffs.

"Think of it this way: Let's say you bought a car, and had your alternator replaced by a local mechanic. Under Apple's strategy, your car would no longer start because you didn't bring it to an official dealership. They intentionally disable your car because you tried to fix it yourself," PCVA wrote. "That is wrong, and we hope to prove that it violates various consumer protection laws in the United States."

Error 53 has been in the news recently.

The error message appears on iPhone 6, 6S, 6 Plus and 6S Plus devices whose Home button -- which includes the Touch ID sensor -- and/or cable have been replaced by a do-it-yourself owner or a third-party repair shop. Once the error appears, the iPhone is "bricked," or rendered unusable.

The error is triggered when users update/upgrade to a new version of iOS -- some reports have attributed it to iOS 9, but reports of the problem precede iOS 9's release -- when connected to a personal computer via iTunes. It's unclear whether updating/upgrading "over the air" -- cutting iTunes out of the loop -- has the same affect.

Kyle Wiens, the founder of iFixit.com, whose site has been tracking the issue since late 2014, said over-the-air updates did not provoke Error 53. "I've heard that the over-the-air update just fails, while doing the update via iTunes is what bricks the device," Wiens said in an email reply to questions today.

Apple said the error and subsequent disabling of the iPhone is a security precaution.

"Error 53 is the result of security checks designed to protect our customers," an Apple spokesperson said in an emailed statement. "iOS checks that the Touch ID sensor in your iPhone or iPad correctly matches your device's other components. If iOS finds a mismatch, the check fails and Touch ID, including for Apple Pay use, is disabled. This security measure is necessary to protect your device and prevent a fraudulent Touch ID sensor from being used."

Specifically, Error 53 pops up when iOS's checks determine that the Touch ID sensor and/or cable connecting it to the logic board don't have the proper "pairing."

Some users immediately smelled conspiracy, and claimed that Apple is using Error 53 to block customers from do-it-yourself and third-party repairs, which are often less expensive than Apple's own fees -- and in many locales where Apple does not have a physical presence, the only available option.

Others defended Apple on the company's support forums when iPhone owners asked for advice on what to do after Error 53 had crippled their smartphones, and blasted the questioners for not having Apple itself repair their devices.

"You've voided your warranty and all service & support options from Apple, and that includes this forum," chided "TJBUSMC1973" in a Feb. 6 message on one thread. "Please seek an answer to your query elsewhere. Thank you and have a good day."

Wiens decried Apple's practice. "Whatever Apple's reasoning, Error 53 doesn't make us very happy," Wiens wrote last week in a long post to his site's blog. "Owners have the right to repair their products and get them repaired by technicians they trust," he added in his email to Computerworld.

Once an iPhone is made inoperable by Error 53, an owner's options are limited: Replace the original Home button (which includes the Touch ID sensor) and original cable, assuming they are still available; or buy a new iPhone.

Wiens suggested an alternative. "Apple should be providing a tool for people to calibrate their device to the new [Touch ID] sensor," he said in his email. "Or they should allow the user to disable the [Touch ID] sensor." Users could be required to prove that they were the rightful owners by entering their unlocking PIN.

Coincidentally, iFixit and others, including the Electronic Frontier Foundation (EFF) and groups representing repair technicians, recently rebranded the Digital Right to Repair Coalition as the Repair Association. The association has lobbied for pro-repair legislation in several states.

Wiens is on the Repair Association's board, and said that the organization had not had any direct communication with Apple over Error 53.