Nineteen times the price. Four more channels.

Five scanners, one fault, one car. Car and Driver made the fault rather than waiting for it — unplugging the mass-air-flow sensor on a 2005 Corolla until the light came on — then plugged each scanner into the same car, counted what it could read and timed how long it took to show the code. This is its August 2026 re-test.

The dearest reads four more than the cheapest

Live data channels, or parameter IDs, are what this category is compared on: how many things about the running engine the tool can show you at once. Here is how that count moves across a price range of roughly 19 to 1.

We do not print prices — they go stale, and the retailer’s own page is where the current one lives. The tiers below are ours, assigned from the prices Car and Driver listed when we read its test: budget, mid, upper, premium, spanning that range in that order. They are a comparison made on that day, not a statement about what anything costs now.

The cheapest tool reads 16 channels. The dearest reads 20. The fewest of all, 12, came from the BlueDriver, a mid-tier tool. The TOPDON is left out of the comparison because Car and Driver counted every channel it lists, active or not, and says so.

What you are actually paying for

So what does the money buy? One thing, and it is not on most listings in plain language: bidirectional control. A read-only scanner tells you what the car thinks. A bidirectional one can command it — retract an electronic parking brake for a brake job, bleed the ABS, run an actuator test — which is how you tell a failed part from a failed sensor reporting a healthy one.

Car and Driver describes two of the five as bidirectional, and they are the premium-tier Autel and the upper-tier TOPDON. If you are pulling a code to know whether to worry, read-only is the whole job and the budget tool does it. If you are diagnosing a fault to repair it yourself, that is the feature you are buying and the channel count is a distraction.

The one with a subscription

One unit here charges a subscription to keep its updates coming: the Autel, whose first year is included and every year after that is not. The TOPDON, the other bidirectional tool, comes with lifetime updates and no fee. The BlueDriver asks for no subscription but does require an account before it will work.

A recurring charge on a tool you use twice a year is a different product from the one the price tag describes. It is worth checking on any scanner before buying, because it is rarely on the front of the box.

Five scanners, as tested

Three of the five carry a link. The Autel MaxiCOM MK808Z-BT does not: its Amazon listing carries seven ratings, too few to send you to. The BlueDriver Pro Next Gen does not: the listing Car and Driver links is sold as a colour of the original Pro and never names the Next Gen. Checked on amazon.com on 22 October 2026.

What changed. This page used to rest on the November 2025 version of the same test, in which the Gearwrench Everyday Diagnostic Tool read the most channels and was our pick. Car and Driver re-ran it in August 2026 with a new line-up, and the Gearwrench is now among the scanners it lists without figures. We follow the current test rather than a version you can no longer check.

What nobody has measured

1. Code coverage beyond the generic set. Every OBD-II tool reads the standard powertrain codes. Manufacturer-specific codes — the ones that actually name the part — vary hugely by tool and by car, and no published test compares them across brands.
2. Whether the app still exists in five years. Every Bluetooth unit here depends on a phone app or a vendor’s updates. Nothing measures what happens when the company stops, and a corded tool has no such dependency.
3. Accuracy of the live figures. The counts are of how many channels appear, not of whether the numbers in them are right. No test we found put a known signal in and checked what came out.