AU Tool DM303 User manual

www.autooltech.com
Auto Diagnostic Multimeter
AUTOOL DM303
User Manual
用户手册

COPYRIGHT INFORMATION
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mark, domain name, logo, or company name of AUTOOL or any
third party without permission from the owner of the applicable
trademark, service mark, domain name, logo, or company name.
You may contact AUTOOL by visiting AUTOOL at https://www.au-
tooltech.com, or writing to [e-mail], to request
written permission to use materials on this manual for purposes or
for all other questions relating to this manual.
●
●
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All rights reserved by AUTOOL TECH. CO., LTD. No part of this
publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior written
permission of AUTOOL. The information contained herein is
designed only for the use of this unit. AUTOOL is not responsi-
ble for any use of this information as applied to other units.
Neither AUTOOL nor its affiliates shall be liable to the purchaser
of this unit or third parties for damages, losses, costs, or
expenses incurred by the purchaser or third parties as a result
of: accident, misuse, or abuse of this unit, or unauthorized modi-
fications, repairs, or alterations to this unit, or failure to strictly
comply with AUTOOL operating and maintenance instructions.
AUTOOL shall not be liable for any damages or problems
arising from the use of any options or any consumable products
other than those designated as original AUTOOL products or
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Other product names used herein are for identification purpos-
es only and may be trademarks of their respective owners.
AUTOOL disclaims any and all rights in those marks.

TABLE OF CONTENTS
Cautions .............................................................................................................. 1
Safe operation guidelines................................................................................ 1
Product Introduction.......................................................................................... 3
Overview ......................................................................................................... 3
Composite indicator ........................................................................................ 3
Product Structure............................................................................................... 5
Structure diagram............................................................................................ 5
Button function ................................................................................................ 6
Cable Number................................................................................................. 7
Operations Instruction....................................................................................... 8
Functional operation guidelines ...................................................................... 8
Voltage measurement ..................................................................................... 8
Oscilloscope.................................................................................................... 9
Current measurement ..................................................................................... 11
Resistance test................................................................................................ 12
Automotive circuit test ..................................................................................... 13
Car start-up test .............................................................................................. 16
Injector test...................................................................................................... 17
Automobile relay test....................................................................................... 19
Analog signal test............................................................................................ 20
Ignition pulse signal test.................................................................................. 22
K line data ....................................................................................................... 23
CAN bus data.................................................................................................. 25
Frequency measurement ................................................................................ 26
Other Problems .................................................................................................. 27
Software upgrading ......................................................................................... 27
Equipment identification number..................................................................... 27
Maintenance Service.......................................................................................... 28
Maintenance.................................................................................................... 28

Warranty .............................................................................................................. 29
Warranty access.............................................................................................. 29
Disclaimer ....................................................................................................... 29
Return & Exchange Service .............................................................................. 30
Return & Exchange ......................................................................................... 30

CAUTIONS
Safe
operation
guidelines
The automobile diagnostic multimeter is designed and
produced in strict accordance with GB4793.1 Safety Require-
ments for Electronic Measuring instruments and IEC61010
Safety Standard, and conforms to double insulation, overvolt-
age standards (CATII1000V, CATIII600V) and safety
standards of pollution level 2. Please operate the instrument
according to usage instructions in the Manual; otherwise, it
might weaken or lose protection function of the instrument.
Before use, check that the insulation layer of the probe is intact
without damage or breakage. If any obvious damage to insula-
tion of probe or instrument shell, or you believe that the instru-
ment cannot work normally, please do not use the instrument
any more.
While using a probe, put your fingers behind its finger protec-
tion ring.
Do not apply voltage above 1000Vrms between instrument
terminal and grounding terminal to prevent electric shock and
instrument damage.
In case of measured voltage higher than DC60V and 42Vrms,
be careful to prevent electric shock.
Before covering up the rear cover of the instrument, it is strictly
forbidden to use the instrument; otherwise there will be risks of
electric shock.
Measured signals are not allowed to exceed the regulated limit
value to prevent electric shock and instrument damage.
It is not allowed to use current to test terminals or voltage at
current gear.
A self-recovery fuse is used inside the instrument. Do not
change the internal wiring of the instrument to avoid damaging
the instrument and endangering safety.
When the battery symbol is shown in red on the LCD, the
battery should be replaced timely to ensure the measurement
For the correct use of the instrument, please read the full text
of this manual carefully before use, especially the “safety
precautions”.
1

accuracy.
Do not operate the instrument in the high temperature, high
humidity environment. Especially, do not store the instrument
in the wet environment, as the instrument performance may
deteriorate if being wetted.
Clean the instrument enclosure with a wet cloth and a gentle
detergent, and do not use abrasive agents or solvents.
2

3
The automobile diagnostic multimeter is a hand-held new
diagnostic oscillometric multimeter integrating digital oscillo-
scope, digital multimeter, automobile circuit and automobile
signal inspection, which is designed with the embedded digital
control technology.
The multimeter mode can measure the AC / DC voltage and
current, resistance, diode forward voltage drop, on-off and
frequency.
Oscilloscope mode is a complete intelligent measurement
system, which includes signal input, data sampling, data
processing and automatic search, with the waveform test
bandwidth of 500KHZ. With a variable sampling frequency, the
slowly varying signal amount can be measured. It is applicable
to measuring and observing various signals on the automobile
circuit during the car overhaul, including the motor drive signal
and motor power voltage of new energy vehicle, fuel car engine
ignition pulse signal, camshaft signal, crankshaft signal, wheel
speed sensor signal, oxygen sensor signal and so on;
Car circuit detection can online test the low voltage circuit,
prompt high voltage or line leakage and output the power
supply voltage. It can also output the power voltage to test the
parts of the car, or lower the voltage to drive the parts of the
car, such as lights; Test the battery voltage when the oil-fueled
vehicle starts, and judge whether the vehicle starting system
and the battery are in good condition;
The analog signal output can be applied to the car ECU detec-
tion and can simulate the square wave and sine wave output
and simulate the fuel injection signal to drive the fuel injection
nozzle; Check the data signal K line and CAN bus signal in the
vehicle.
PRODUCT INTRODUCTION
Overview ●
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The multimeter function and the oscilloscope function are
integrated together on the instrument. When measuring the
voltage signal using a probe, switch to the oscilloscope function
with
[Fn] key to facilitate the use and observation of signal wave-
form.
Composite
indicator

4
LCD is a 2.8-inch color screen, with a resolution of 320*240;
Input impedance for the voltage measurement: it is 2~3MΩ
when the voltage is lower than 160V; it is 10MΩ when the
voltage is higher than 160V. The maximum input voltage is
1000Vpp; The analog bandwidth is 500KHz; The voltage
range is converted automatically;
The 10A terminal fuse for current measurement is 15A self-re-
covery fuse, and the maximum measurable current is 20A; The
current measurement mA/uA terminal fuse is 0.5A self-recov-
ery fuse, and the maximum measurable current is 200mA;
Working temperature: 0~40°C(32~104°F) Humidity: ≤75%;
Storage temperature: 10~50°C(14~122°F) Humidity: ≤70%;
Altitude: 2000m.
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5
PRODUCT STRUCTURE
Structure
diagram
Display screen Power supply indicatorA B
Button 10A current input
C D
mA/uA measurement
input COM measurement input
E F
Diode, voltage,
resistance, frequency
measurement input
Lighting lamp
G H
DB15 interface
I
A
B
I
C
D
E F
H
G

6
Button
function
Power key
A
HOLD Pause Hold / Measurement key.B
Direction
button Select the functional items.
C
ESC Return key.D
Fn Measurement mode switch key.
EOK Enter key.
F
F2 Function keys, defined by the test function.G
ZERO / F1 Function key, quick reset setting, or
defined by test function.
H
Lighting key Press the light on / off.
I
A
B
C
D
E
H
I
G
F
Press for power-on, press for about 0.3
seconds to turn off the power when it is
on, and long press 3 seconds to reset the
instrument.

7
Cable
number Cable Number
NO. Distribution
Head No.
Name Functions
C01
C01 - 1
Multi-functional
detection line
DC connector,
connected to the
battery clip line
C02
Battery clip line
C03
Ignition pulse
signal detection
line
Sensing high-voltage
line signal
C05Jumper(Black)
C06Jumper(Green)
C07Jumper(Yellow)
C04
C04 - 1
Automotive
circuit detection
line
DC connector,
connected to the
battery clip line
C04 - 2 Probe terminal
C01 - 2 Terminals for
injector test and
Automobile relay test
C01 - K K line signal line
C01 - CAN+ CAN+ signal line
C01 - CAN- CAN- signal line
C01 - GND Ground wire
C01 - SIN Sine wave signal line
C01 - S1 5V signal line
C01 - S2 Square signal line

RedBlack
8
OPERATIONS INSTRUCTION
The instrument is equipped with a power switch and the
automatic sleep function. The automatic sleep time can be set
to 1-30 minutes. The key tone of the instrument can be set to
turn on and off, but the warning tone cannot be turned off. The
brightness of the screen can be set. The brightness can be set
according to the actual operation environment, and the battery
time can be extended by appropriately lowering the brightness.
The help function of the instrument provides a brief operation
description.
The instrument is configured in one or more languages
according to the sales area. Please contact your local dealer
for different languages.
After turning on the power supply, according to the displayed
icon, use the [up / down / left / right] direction keys to move the
current option, and press [OK] to enter the function item.
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Functional
operation
guidelines
Insert the red probe into the “V” jack and the black probe into
the “COM” jack;
●
Voltage
measurement

Voltage（DC）
<HOLD>Hold
<Fn>Function Mode
<F1>Zero
<F2>PULL DOWN
0.00V
9
Insert the red probe into the “V” jack and the black probe into
the “COM” jack. The instrument does not have a dedicated
BNC interface. The oscilloscope is used as an expanded
function of voltage signal detection, which greatly facilitates
user operation and is particularly suitable for vehicle mainte-
nance.
●
The current measured value is displayed. If the voltage fluctu-
ates, press the [HOLD]key to maintain the display status. If
there is no voltage signal, the displayed value is non-zero, the
red and black probe can be shorted, and press the [F1]key at
the same time to perform the quick zeroing operation. [F2]key
is used to remove the induction power at the measurement
point. Press [F2]key during the measurement, which is equiv-
alent to a 10K resistance connected the red and black probe.
This function is suitable for detecting the induction voltage of
the new energy vehicle. Press [Fn]key to switch to the AC
voltage measurement and the oscilloscope mode to observe
the signal waveform; In the voltage measurement or oscillo-
scope mode, the range is automatically converted, and the
maximum measurable voltage signal is 1000V;
In the voltage measurement mode, the probe only inputs
signal, but no pulse signal, without interference to the
measured point.
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●
Oscilloscope
Enter the function item, displayed as shown below:
●

5V/di v 1mS
0V
U: 0.00V MIN: 0.00V MAX: 0.00V
Trig. +00
10
Display the current signal waveform, 5V/grid - display the
voltage scale value, and press the [up]and [down]keys to
change during measurement; 1ms-scan time scale value;
during measurement, press the [left]and [right]keys to
change; Trigger+01 - displays the correction value of the
trigger level, which can be changed by pressing [F1 / F2]. The
trigger level is the average value of the current waveform
automatically calculated. The positive value of trigger correc-
tion indicates the increase value of trigger level correction, and
the negative value of trigger correction indicates the decrease
value of trigger level correction;
Press the [HOLD]button to pause the display of the waveform.
When the waveform is suspended, the [up / down / left / right]
keys can be used for the left and right movement control of the
waveform, so as to facilitate the comparison and observation
of the waveform.
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●
Enter the function item, displayed as shown below:
●
RedBlack

Ampere(DC) mA(Green)
<HOLD>Hold
<Fn>Function Mode
<F1>Zero
<F2>20A/mA
0.0mA
Below 200mA Above 200mA
Red Black Red Black
11
In the process of voltage signal measurement, the instrument
automatically changes the range and the maximum measur-
able voltage signal is 1000V;
●
Enter the function item, displayed as shown below:
●
Measure the current below 200mA, insert the red probe into
the green “mAuA” jack, and insert the black probe into the
“COM” jack;
Measure the current above 200mA, insert the red probe into
the yellow “A” jack, and insert the black probe into the “COM”
jack;
●
The current measured value is displayed. If the current fluctu-
ates, press the [HOLD]key to maintain the display status. If
there is no current signal, the displayed value is non-zero, the
red and black probe can be shorted, and press the [F1]key at
the same time to perform the quick zeroing operation. [F2]key
is used to switch the large current measurement, [Fn]key is
used to convert measurements of DC current and AC current.
●
●
Current
measurement

Ampere(DC) 10A(Yellow)
<HOLD>Hold
<Fn>Function Mode
<F1>Zero
<F2>20A/mA
0.00A
RedBlack
12
●
Enter the function item, displayed as shown below:
●
Insert the red probe into the “Ω” jack and the black probe into
the “COM” jack;
●
Press [F2]key and switch to detect high current mode as
shown below:
●In the high current mode, the maximum measurable current is
20A and the maximum measurable continuous current is 10A.
There is 15A 30V self-recovery fuse inside, which can protect
the instrument from damage due to excessive current in the
use of vehicle detection. However, the detection of current in
220V / 380V strong current circuit cannot prevent damage
caused by excessive current, and cannot exceed the measur-
able current range during use.
Resistance
test

Resistance
<HOLD>Hold
<Fn>Function Mode
<F1>Zero
Diode： . V
0.00Ω
Diode/Short
<HOLD>Hold
<Fn>Function Mode
<F1>Zero
Resistance： . Ω
0.00V
13
●
Insert the special wire for automobile circuit into the multi-func-
tional interface (top of the machine), connect the battery clip
line, clamp the red clip on the positive plate of the automobile
battery, clamp the black clip on the negative plate of the
automobile battery, and use the probe to detect the automobile
circuit. During the detection process, the probe will send a test
signal to detect the electric leakage of the circuit.
●
The instrument detection resistance and the diode are
two-in-one function display. Press [Fn]key to switch the
display mode. When measuring the resistance, the resistance
can be set as the main display; when measuring the diode, the
diode can be set as the main display; As shown in the following
figure:
●The resistance value displayed is the resistance value when
measuring the resistance, and the voltage value displayed is
the pressure drop value when measuring the diode. Connect
the red and black probe, and press [F1]key for zeroing. If the
resistance is excessive low, the instrument will give a sound
prompt.
Automotive
circuit test

Voltage(DC)
<HOLD>Hold
Supply voltage: 12.50V
<UP>SHORT TO B+
<F1>Zero
<DOWN>SHORT TO B-
0.00V
Red
Red
Black
C04 - 1C04 - 2
C04
C02
14
Enter the function item, displayed as shown below:
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●
Connecting the battery for power supply, the instrument will
obtain the external power;
The instrument displays the current probe voltage value and
the voltage value of the power clip;
Insert the probe into the COM port of the instrument, showing
the voltage is zero; if not zero, press [F1]key to zero;
Detect the circuit on the automobile using a probe, showing the
current detection voltage. If the voltage is a constantly chang-
ing signal, press [Fn]key to enter the oscilloscope for observa-
tion; if the detected voltage is lower than 0.7V, the instrument
will automatically detect the leakage; if the figure with blue
background is displayed and there is a sound prompt, it
indicates that the circuit resistance to ground is lower than
Test signal

12.40V
Voltage(DC)
<HOLD>Hold
Supply voltage: 12.50V
<UP>SHORT TO B+
<F1>Zero
<DOWN>SHORT TO B-
0.00V
Voltage(DC)
<HOLD>Hold
Supply voltage: 12.50V
<UP>SHORT TO B+
<F1>Zero
<DOWN>SHORT TO B-
15
If the detected voltage is very high and close to the power
supply voltage, the instrument will display a number on the red
background with a sound prompt, indicating that the circuit
voltage is high, which may be a power supply line. If it is an
insulated line, it indicates that the line is leaking to the power
supply, as shown in the following figure:
Probe power supply function on instrument line: Press the [up]
function key, and the probe outputs the power supply voltage;
Probe grounding function on instrument line: Press the [down]
function key, and the probe is short circuited to the negative
pole of the power supply;
Test function of automotive electrical appliances: The instru-
ment outputs a power supply voltage value through the probe
to drive the automobile electrical appliances to work. It judges
whether the electrical appliances are damaged by observing
whether the electrical appliances are working, or drive the
automobile electrical appliance through short connecting the
special probe to the negative pole, and then judge whether the
electrical appliance is damaged by observing whether the
electrical appliance is working. For example, check whether
the turn signal is intact and use the probe to detect the current
voltage value of the two leads of the lamp. If both lines are
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10K. If the circuit is insulated to ground, it indicates that the
circuit has leakage, as shown in the following figure: