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Buying guide · updated 2026-10-06 · The Real Deal Meter team
Car diagnostic tools under $400 compared
Four tools under $400, and they do three different jobs. One is a scan tool that talks to every module in the car and can tell a part to move. Two are the same key programmer, Autel’s KM100, from two listings. One cleans and tests fuel injectors on a bench. Most people who end up here want the first, so this page starts by sorting out which job is yours, then says what each of the other two needs that is not in the box.
| Product | Price | ||
|---|---|---|---|
| For injectors, on the bench | AUTOOL CT160 Fuel Injector Cleaner & Tester Cleans four injectors at a time in a heated ultrasonic bath, then runs spray, leak and flow tests with a pressure gauge. The injectors come out of the engine to use it. 8 checks since Sep 28 · low $225.01 | ||
| The one most people want | Autel MaxiCOM MK808S Bidirectional Scan Tool (wired OBD2) A 7-inch Android scan tool on a cable: codes from every module, bidirectional tests and about 28 service resets, the oil reset among them. No battery tester; the Bluetooth MK808BT Pro adds one. 10 checks since Sep 26 · low $340.15 | ||
| Key programmer, two keys in the box | Autel MaxiIM KM100 Key Programmer with 2 IKEY Smart Keys Generates a key on Autel’s own IKEY blanks in about a minute, reads, writes and clones transponders, and learns keys to the immobilizer over OBD on the makes Autel lists. Two IKEYs come with it. 8 checks since Sep 23 · low $363.25 | ||
| The same tool, another listing | Autel MaxiIM KM100 / KM100X Key Fob Programmer The KM100 from Autel’s Choice Direct store, in a listing that names both the KM100 and the KM100X — check which one ships. Autel’s US page gives one year of updates; this listing says lifetime, so ask which applies. 13 checks since Sep 23 · low $369.36 |
Prices last checked 2026-10-05. Each one is re-checked daily and this table is rebuilt when any of them moves.
More car diagnostic tools at the stores we work with ↓
Paid links · We may earn a commission if you buy through them.Three jobs, so start with yours
A scan tool is for finding out what is wrong. The MK808S is a 7-inch tablet that plugs into the car’s OBD port by cable, runs active tests and about 28 service functions, the oil reset among them 1.
A key programmer is for making keys. The KM100 generates a key in about a minute, reads, writes and clones transponder chips, and does immobilizer learning 2. That is a locksmith’s or a dealer’s job more often than a home mechanic’s.
An injector machine is for injectors that are already out of the engine. The CT160 cleans four at once in a heated ultrasonic tank and then tests how they spray, leak and flow 3. If you are not pulling injectors, it is not for you.
- Autel MK808S vs MK808BT Pro vs MK900BT OBDPRICE — MK808S: 7-inch 1024 x 600 screen, wired; active (bidirectional) tests; about 28 service functions including the oil reset and auto VIN; no battery testing, which the MK808BT Pro adds
- MaxiIM KM100 Autel — the maker's page: one-minute key generation on Autel IKEY keys; chip read, write, cloning and frequency detection; key and remote learning; IMMO programming for brands including BMW, Volkswagen, Honda and General Motors; 2 IKEYs and a Bluetooth VCI (V200) in the box; a separate adapter kit for some BMW/Mini and VW/Audi work; 5.5-inch screen; one year of free software updates
- Autool CT160 4-Cylinder Car Petrol Injector Cleaner and Tester Auto Supply — 4 injectors tested at once; ultrasonic cleaning, 1300 ml tank, 40 kHz, 70 W, heated detergent; idle, medium, high-speed, accelerating and variable-speed tests, leakage and spray tests; uniformity detection and atomization observation; pressure gauge
A code is where diagnosis starts, not where it ends
A basic reader shows the fault codes a car has stored. What a code rarely says is whether the part it names has failed, or the wiring to it. That is the gap a bidirectional tool closes: it can tell a component to work — the MK808S lists these active tests 1 — so you can watch a fan start or hear a valve click and know which half of the circuit is at fault.
What the MK808S leaves out is battery testing, which Autel puts in the Bluetooth MK808BT Pro instead 1.
- Autel MK808S vs MK808BT Pro vs MK900BT OBDPRICE — MK808S: 7-inch 1024 x 600 screen, wired; active (bidirectional) tests; about 28 service functions including the oil reset and auto VIN; no battery testing, which the MK808BT Pro adds
What a key programmer needs besides itself
The KM100 makes keys on Autel’s own IKEY blanks, and two come in the box with the tablet and a Bluetooth VCI. Autel lists immobilizer programming for makes including BMW, Volkswagen, Honda and General Motors, and sells a separate adapter kit for some BMW, Mini, VW and Audi work 1. So before you buy, look up your own car in Autel’s coverage, and count the blanks you will need.
Updates matter here more than anywhere: a key tool is only as good as its list of cars. Autel’s US page includes one year of free software updates 1; one of the two listings here says lifetime. Ask the seller which is true before you pay.
- MaxiIM KM100 Autel — the maker's page: one-minute key generation on Autel IKEY keys; chip read, write, cloning and frequency detection; key and remote learning; IMMO programming for brands including BMW, Volkswagen, Honda and General Motors; 2 IKEYs and a Bluetooth VCI (V200) in the box; a separate adapter kit for some BMW/Mini and VW/Audi work; 5.5-inch screen; one year of free software updates
What these prices mean
Each price here is the one we last checked on that product’s own page, and each page says the date. All four are AliExpress listings: AliExpress quotes new accounts a lower “Welcome deal” price and runs store coupons on top, so you may be shown less than we list.
The struck-through figures are the sellers’ own list prices, and they claim between about 45% and 70% off. We have not seen any of these tools charged near its list price in our record, which is why the Deal Meter measures them against the prices we recorded ourselves.
More at the stores we work with
1 more car diagnostic tools at $400 or less, besides the ones compared above: each store’s own product at its own price, linked straight to the store. We have not compared these, and their prices are not ones we check.
AliExpress 1
AliExpress’s own prices, read Oct 6, 2026 · AliExpress US local stock: ships from a US warehouse
TOPDON ArtiDiag600S OBD2 Scanner Diagnostic Tool Code Reader Oil/BMS/ABS/SAS/EPB/DPF/TPMS/$178.00 AliExpress list $292.94See it at AliExpress → Paid link
More at AliExpress → Paid link
The stores’ prices are their own, read from the product feed each gives its affiliates and re-read every day; we have not checked them the way we check the deals we track. Stores in alphabetical order, each cheapest first — never in the order of what we earn.
Paid links · Every store link here goes to the store through our affiliate network, and we may earn a commission — see Disclosure.Prices are what we last checked on each product's own page — follow a link for the current price and the date it was verified. Every outbound link here is an affiliate link; see Disclosure.
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