AUTOOL DM303 Automotive Diagnostic Multimeter & Oscilloscope
The AUTOOL DM303 is an advanced handheld diagnostic meter designed for automotive electrical and electronic troubleshooting. It combines a True RMS digital multimeter, digital oscilloscope, automotive circuit tester and vehicle signal diagnostic functions in one portable instrument.
It is suitable for technicians working on cars, trucks, buses, motorcycles and supported electrical systems in hybrid or electric vehicles. The DM303 helps inspect circuits, sensors, actuators and signal waveforms without requiring several separate testing instruments.
Four Integrated Diagnostic Tools
• True RMS digital multimeter
• Automotive digital oscilloscope
• Vehicle circuit testing system
• Automotive signal diagnosis and output
Main Functions
• DC and AC voltage measurement
• DC and AC current measurement
• Resistance measurement
• Frequency measurement
• Diode and continuity testing
• Oscilloscope waveform observation
• Cranking-system testing
• Ignition-pulse signal testing
• Fuel-injector signal testing
• Compatible injector drive testing
• Automotive relay testing
• Vehicle circuit voltage testing
• Controlled automotive circuit drive output
• Square-wave and sine-wave signal output
• K-line and CAN-bus line observation
• Camshaft and crankshaft sensor signal checking
• Wheel-speed sensor signal checking
• Oxygen-sensor signal checking
• Motor drive-signal and power-voltage measurement
True RMS Digital Multimeter
The AUTOOL DM303 supports auto-ranging True RMS measurements for greater flexibility when diagnosing automotive and general electrical circuits.
Supported measurements include:
• DC voltage
• AC voltage
• Current
• Resistance
• Frequency
• Diodes
• Circuit continuity
Digital Oscilloscope
The integrated oscilloscope allows technicians to view changing electrical signals as waveforms. This is useful for analyzing automotive sensors, actuators, ignition signals and other signals that cannot be diagnosed accurately using voltage values alone.
Possible automotive applications include:
• Ignition pulse signals
• Crankshaft sensor signals
• Camshaft sensor signals
• Oxygen sensor signals
• Wheel-speed sensor signals
• Fuel-injector control signals
• Relay activation signals
• Motor drive signals
• K-line and CAN-line activity
The manufacturer’s product page lists a maximum analog bandwidth of 500kHz, while some manual versions may show a different value. Confirm the specification of the supplied hardware and manual when oscilloscope bandwidth is critical.
Injector and Relay Testing
The DM303 provides dedicated modes for testing supported electromagnetic fuel injectors and automotive relays. It can observe injector signals and provide supported drive signals for component testing.
The injector test does not support 120V injectors. Always identify the injector type, pinout, operating voltage and current before applying any output.
Analog Signal Output
The device supports selected signal outputs, including:
• 5V square-wave signal
• 5V peak-to-peak sine-wave signal
• 12V square-wave signal
• Adjustable injector drive signals
These functions can assist with controlled component testing and simulated signal diagnosis when used according to the vehicle wiring diagram and component specifications.
K-Line and CAN-Bus Observation
The AUTOOL DM303 can observe electrical activity on supported K-line and CAN-bus lines for circuit-level diagnosis.
This function does not make the DM303 a complete OBD diagnostic scanner. It does not replace a professional scan tool for reading vehicle modules, diagnostic trouble codes or live data.
Cranking and Ignition Analysis
Dedicated automotive modes allow technicians to observe voltage behavior during engine cranking and inspect ignition pulse signals. These functions help identify abnormal battery voltage drops, starter-system problems and ignition-signal irregularities.
2.8-Inch Color Display
The 2.8-inch adjustable color display presents measurements, menus and waveforms clearly. The built-in stand allows the device to remain upright on a workshop bench while both hands are used for testing.
Technical Specifications
• Model: AUTOOL DM303
• Display: 2.8-inch color screen
• Voltage range: DC 0–1000V
• AC voltage range: 0–700V
• Current ranges: 0–20A and 0–200mA
• Resistance range: 0–1MΩ
• Frequency range: 1Hz–1MHz
• Listed oscilloscope bandwidth: Up to 500kHz
• Automotive circuit drive current: 0–5A
• Injector drive signal: 500–6000rpm
• Operating temperature: 0°C to 40°C
• Power option: 4 × 1.5V dry batteries
• Alternative power: Compatible rechargeable lithium battery configuration
• Measurement type: Auto-ranging True RMS
Power Supply
The unit can operate using four 1.5V dry batteries. A compatible lithium-battery configuration may also be supported according to the supplied device version.
Dry batteries must never be charged inside the unit. Batteries are normally not included in the package.
Common Applications
• Automotive electrical troubleshooting
• Sensor signal analysis
• Injector and relay testing
• Cranking and ignition diagnosis
• Wiring and continuity inspection
• ECU-related circuit inspection
• CAN and K-line electrical observation
• Automotive training laboratories
• Mobile vehicle electrical service
• Traditional, hybrid and supported electric-vehicle circuit work
Package Contents
• 1 × AUTOOL DM303 Main Unit
• 1 × Multifunction Test Lead
• 1 × Battery Clip Cable
• 1 × Set of Multimeter Probes
• Jumper and Adapter Cables
• Additional Automotive Test Leads
• 1 × Portable Protective Toolbox
• 1 × User Manual
• 1 × Retail Package
Batteries are not included. Package contents may vary according to the supplied version, so verify the included accessories before purchasing.
Important Safety Information
Do not apply an output signal to an unknown wire, powered communication line, ECU output, airbag or SRS circuit. Always identify the circuit, pinout, allowable voltage and current before using a drive or simulation function.
When working on hybrid or electric vehicles, follow the manufacturer’s high-voltage safety procedures. The presence of a 1000V measurement range does not by itself make every supplied probe, accessory or test procedure suitable for high-voltage traction systems.
Disconnect power when performing resistance, diode or continuity measurements unless the vehicle procedure specifically states otherwise.
Use the correct input terminal and measurement mode before connecting the probes. Incorrect settings or connections may damage the tester, vehicle electronics or the component under test.
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