AUTOOL DM303 Automotive Diagnostic Multimeter
US$199.00
- True RMS DMM + Oscilloscope
- Cranking, Ignition + Vehicle Signals
- Injector + Relay Testing
- 5 V / 12 V Signals + K/CAN View
- True RMS DMM + Oscilloscope: Combine True RMS auto-ranging electrical measurements with oscilloscope waveform observation.
- Cranking, Ignition + Vehicle Signals: Check cranking behavior, ignition pulses, and dedicated vehicle signals from one handheld unit.
- Injector + Relay Testing: Use the supported drive and observation modes for electromagnetic injectors, excluding 120 V injectors, plus compatible relays.
- 5 V / 12 V Signals + K/CAN View: Generate 5 V square, 5 Vpp sine, or 12 V square signals and observe K/CAN line data in the dedicated modes.
- 2.8-Inch Multi-Language Screen: Read menus on the brightness-adjustable color screen and carry the tester with its leads in the toolbox.
- True RMS DMM + Oscilloscope: Combine True RMS auto-ranging electrical measurements with oscilloscope waveform observation.
- Cranking, Ignition + Vehicle Signals: Check cranking behavior, ignition pulses, and dedicated vehicle signals from one handheld unit.
- Injector + Relay Testing: Use the supported drive and observation modes for electromagnetic injectors, excluding 120 V injectors, plus compatible relays.
- 5 V / 12 V Signals + K/CAN View: Generate 5 V square, 5 Vpp sine, or 12 V square signals and observe K/CAN line data in the dedicated modes.
- 2.8-Inch Multi-Language Screen: Read menus on the brightness-adjustable color screen and carry the tester with its leads in the toolbox.
- 3-Year Warranty Main unit 3 years · Accessories 1 year
- 90-Day Returns Eligible returns within 90 days
- Official Store Genuine products · Direct support
AUTOOL DM303 · Automotive Multimeter and Oscilloscope
Bring Vehicle-Focused Electrical Tests Together
Bring vehicle-focused electrical measurements, waveform observation, and selected component tests into one handheld kit. DM303 supports cranking and ignition checks, compatible injector and relay tests, signal output, and K/CAN line viewing in dedicated modes for broader vehicle-circuit work across workshop and mobile service tasks.
- DMM + Automotive Scope
- Cranking + Ignition Modes
- Injector + Relay Test Modes
- 5 V / 12 V Signal Outputs
- K / CAN Line Observation
Key Features
Meter, Scope and Automotive Signal Tools
True RMS Auto-Ranging Multimeter
Measures DC / AC voltage, current, resistance, diode, and frequency. Auto range helps reduce manual range selection, while True RMS improves reading reliability for electrical testing.
Oscilloscope Mode
The product page lists 500 kHz analog bandwidth, while the current model PDF lists 200 kHz. Confirm the delivered hardware, firmware and manual version before choosing DM303 for a bandwidth-dependent task; neither figure is the sampling rate.
Automotive Circuit Test
Supports automotive circuit voltage and drive-current checks. It can help check battery voltage, vehicle circuits, ECU-related wiring, and other electrical parts through the proper test leads.
Injector And Relay Test
DM303 lists drive and observation modes for supported electromagnetic injectors, excluding 120 V injectors, plus relay testing. Confirm component type, pinout, supply, current and permitted output mode; never drive an ECU output, SRS, data line or unknown module.
Analog Signal And K/CAN Line Data
The listed outputs are 5 V square, 5 Vpp sine and 12 V square. Use them only on a documented permitted load and pin after confirming source impedance/current limits for the delivered version; do not inject into powered data lines, ECU outputs, SRS or unknown modules. K/CAN observation is not a full vehicle scan.
Dedicated Automotive Test Modes
DM303 adds injector, relay, cranking, signal simulation, and K/CAN line checks to multimeter and oscilloscope functions. Injector testing does not support 120V injectors.
Color Screen, Multiple Languages
The brightness-adjustable 2.8-inch color screen presents test menus in multiple supported languages, including English, French, Spanish, German, and Chinese.
Portable Electrical Test Kit
The toolbox stores DM303 and its test leads together for transport and organized storage.
Flexible Battery Setup
Use compatible dry batteries or an optional compatible lithium battery, purchased separately. Only the rechargeable lithium battery option may be charged through the device.
Handheld Controls And Connections
DM303 brings its display, navigation keys, and separate measurement inputs into one handheld unit with a rear stand.
3 Years Warranty Support
Main unit: 3-year warranty. Standard accessories: 1-year warranty. Warranty Policy.
Service Workflow
Select the Vehicle Test and Verify Connections
Define the Measurement
Use the wiring diagram to identify the expected signal, reference point and safe measurement mode.
Inspect Leads and Ratings
Confirm the instrument, terminal, fuse, lead and probe ratings for the selected task before connecting.
Select the Mode
Choose the supported voltage, current, resistance, continuity, frequency or other model-specific function and start on a safe range.
Qualify Active Output
Before injector, relay or signal output, confirm component type, pinout, supply, permitted mode, current and source-impedance limits. Keep output off ECU outputs, SRS circuits, powered data lines and unknown modules.
Probe the Circuit
Connect to the correct reference and test point without bridging terminals; use back-probing accessories only where appropriate.
Record and Verify
Save or note the value and operating state, then compare it with the vehicle specification and a second check before assigning a root cause.
Safe Use
Control Output, Bus and Input Connections
Limit Active Output
Injector drive and 5 V square, 5 Vpp sine or 12 V square outputs require a documented permitted pin and load. Output amplitude alone does not define safe current, impedance or duty for an unknown circuit.
Dry Battery Option
You can install 4pcs 1.5V dry batteries for normal use. Do not charge dry batteries through the device.
Charge Only Lithium Setup
If a compatible rechargeable lithium battery is installed, it can be charged. Dry batteries must not be charged.
Batteries Are Not Included
DM303 / DM301 is shipped without batteries due to shipping and battery restrictions. Batteries need to be purchased separately.
Lithium Battery Option
You may install a compatible lithium battery by yourself. The reference image shows a 503450 3.7V 1000mAh lithium battery style.
Interpret the Result in Context
Keep measurement, waveform, protocol observation and active output as separate modes. A meter fuse or input rating does not authorize power or signal injection into an ECU, SRS circuit, sensor or data line.
Result Guide
Read the Result Before Deciding the Next Step
Cranking Test
During vehicle starting, a minimum battery voltage above 9.6V is generally considered normal. If the value drops below 9.6V, the battery may be aging or weak.
Model Comparison
Choose the Right Electrical Test Tool
Model Guide
Choose one or more models. DM303 is selected by default.
| Product Name | DM301 | DM303 | DM208 |
|---|---|---|---|
| Measurement & Readout | |||
| Display Screen | 2.8-inch Color Screen | 2.8-inch Color Screen | 2.4-inch, 320 × 240 |
| Languages | 13 Types | 13 Types | Not stated |
| Voltage Measurement Range | AC: 0-700V DC: 0-1000V | AC: 0-700V DC: 0-1000V | Not stated |
| Current Measurement Range | 0–20 A (20 A maximum; 10 A continuous); 0–200 mA | 0–20 A (20 A maximum; 10 A continuous); 0–200 mA | Not stated |
| Resistance Measurement Range | 0-1MΩ | 0-1MΩ | Not stated |
| Frequency Measurement Range | 0-1MHz | 0-1MHz | Not stated |
| Data Lock/Clear | ✓ | ✓ | Not stated |
| Automotive Functions & Fit | |||
| Basic Functions | 6 Types | 12 Types | Not stated |
| Automotive Circuit Drive Current | × | Maximum Output: 5A Maximum Input: 5A | Not stated |
| Fuel Injector Drive Signal Output | × | 500-6000rpm | Not stated |
| Detection Mode | Voltage Measurement Current Measurement Resistance Measurement Frequency Measurement Oscilloscope Mode Ignition Pulse Signal Testing | Current Measurement Resistance Measurement Frequency Measurement Oscilloscope Mode Fuel Injector Testing Relay Testing Automotive Circuit Testing Automotive Starting Testing Signal Simulation Testing CAN Line Data Reading Ignition Pulse Signal Testing K/LIN Line Data Reading | Not stated |
| Applicable Vehicle Models | Trucks, Sedans, Buses, Electric Vehicles, and Other Vehicle Types | Trucks, Sedans, Buses, Electric Vehicles, and Other Vehicle Types | Not stated |
| Power & Equipment | |||
| Power Supply Method | Dry Battery TYPE-C [Optional] Lithium Battery | Dry Battery TYPE-C 12V Rechargeable Battery [Optional] Lithium Battery | Built-in 2000 mAh lithium battery |
| Accessories | 2 Types of Test Leads | 6 Types of Test Leads | Not stated |
| Flashlight Function | ✓ | ✓ | Not stated |
| Equipped Toolbox | ✓ | ✓ | Not stated |
| Product Details | |||
| Infrared resolution | Not stated | Not stated | 32 × 32 |
| Frame rate | Not stated | Not stated | 7 frames/second |
| Temperature range | Not stated | Not stated | -20°C to 550°C |
| Thermal accuracy | Not stated | Not stated | ±2°C or 2% (maker specification) |
| Emissivity | Not stated | Not stated | 0.10 to 1.00 adjustable |
Manual & Support
Find the Manual and Measurement Guidance
AUTOOL DM303 User Manual
Open the PDF manual for AUTOOL DM303 multimeter and oscilloscope modes, cranking and ignition checks, injector and relay tests, signal output, safety and troubleshooting support.
Package Contents
See What Comes in the Box
- Main UnitAUTOOL DM303 auto diagnostic multimeter
- StoragePortable protective toolbox and retail box
- DocumentationUser manual
- Test LeadsMultifunction test lead, battery clip cable, multimeter probes, jumper / adapter cables, and additional test leads
- BatteryNotice Batteries are not included. Use 4pcs 1.5V dry batteries or a compatible lithium battery setup according to the battery rules.
Buyer Questions
Electrical Connection and Measurement Questions
Does AUTOOL DM303 Include Batteries?
No. DM303 / DM301 is shipped without batteries. You need to buy batteries separately. You can use 4pcs 1.5V dry batteries, or install a compatible lithium battery setup by yourself.
Can I Charge Dry Batteries Inside DM303?
No. Do not charge dry batteries. Only a compatible rechargeable lithium battery setup can be charged. If you are not sure whether your battery is rechargeable or compatible, contact AUTOOL Store before charging.
What Lithium Battery Style Is Shown For DM303?
The reference image shows a 503450 3.7V 1000mAh lithium battery style. Confirm the connector, size, and compatibility before installing a lithium battery.
What Is The Difference Between DM301 And DM303?
DM301 focuses on basic measurement functions such as voltage, current, resistance, frequency, oscilloscope, and ignition pulse signal testing. DM303 adds more automotive diagnostic functions, including fuel injector testing, relay testing, automotive circuit testing, cranking test, signal simulation, CAN line data reading, and K/LIN-related line data reading.
Does DM303 Support Injector Testing?
Yes. DM303 can drive supported electromagnetic injectors, including supported GDI injectors, and can detect real-time injector signals; it does not support 120V injectors. Confirm injector type, pinout, supply, current, and the vehicle procedure before output. A drive response does not by itself prove spray pattern, flow, or root cause, and active output must stay off ECU outputs, SRS circuits, powered data lines, and unknown modules.
What Does The Cranking Test Result Mean?
During vehicle startup, DM303 records the minimum battery voltage and uses 9.6V as a general reference. A lower reading can indicate a weak or aging battery or a starting-system issue that needs further inspection. Apply the battery maker or vehicle procedure for the battery type, temperature, and state of charge.
What Measurement Ranges Does DM303 Support?
The page lists DC 0–1000V and AC 0–700V voltage, 0–20A and 0–200mA current, 0–1MΩ resistance and 1Hz–1MHz frequency ranges. The manual distinguishes 20A maximum from 10A continuous current. These values remain subject to the selected terminal, mode, probe and CAT conditions.
Can DM303 Replace A Full Vehicle Diagnostic Scanner?
No. DM303 is an automotive diagnostic multimeter and circuit / signal testing tool. K/CAN line data reading helps with circuit-level diagnosis, but it should not be described as a complete vehicle diagnostic scanner.
What Accessories Are Included?
Package contents: DM303 main unit, user manual, retail box, portable toolbox, multifunction test lead, battery clip cable, multimeter probes, jumper / adapter cables, and additional test leads. Batteries are not included.
Which Languages Does DM303 Support?
DM303 supports a multi-language interface, including English, French, Portuguese, Polish, Spanish, Japanese, Russian, Italian, German, Dutch, Korean, Chinese, and other supported firmware options. If a specific language is required, confirm before ordering.
How Long Is The Warranty?
Main unit: 3-year warranty. Standard accessories: 1-year warranty. Warranty Policy.
Bill ✓ Verified Purchase –
I’ve been using the DM303 multimeter and it’s been a great help.
I’ve been using the DM303 multimeter and it’s been a great help. The 2.8-inch color screen is clear and easy to read in different working conditions. The oscilloscope works well for checking automotive signals, and the auto range and true RMS make measurements accurate. It comes with plenty of test cables, supports multiple languages, and the plastic toolbox keeps everything organized and protected. Very reliable for auto repair work.
Noah ✓ Verified Purchase –
Reliable relay testing, machine trigger testing, and efficient injector…
Reliable relay testing, machine trigger testing, and efficient injector operation Precise automotive circuit analysis and analog signal analysis Wide-range and efficient performance Convenient and easy operation High-quality materials Reliable K/CAN test system
Luke ✓ Verified Purchase –
I've been using it for a month and it hasn't let me down, it's been wonderful…
I’ve been using it for a month and it hasn’t let me down, it’s been wonderful, and today it was very helpful in detecting a problem. I highly recommend it.