Autodata - Diagnostic Trouble Codes Fault locations and probable causes - 2004 edition

Tools & equipment
Test equipment
Multi-meter types
The majority of electrical faults identified in this manual can be successfully diagnosed using an ohmmeter or voltmeter.
Normally these functions will be combined in a multi-meter.
A high impedance (1 0 K ohmslvolt minimum) multi-meter that includes a 0-20 V voltage scale and a low (0-200) and high
(0-20 K) range ohm scale is recommended for measuring the voltage and resistance of the system components.
Analogue meters (with a needle sweeping across a numerical scale),-due to their continuous readout are useful for certain
applications, such as counting needle deflections to identify fault codes on certain models and the identification of
intermittent faults, but for general workshop use a digital meter is easier to use and is more resistant to rough handling and
less likely to be damaged by incorrect use.
Digital meters (with an LED or LCD display), are available in many different types. In addition to the basic, general purpose
meters with voltage (DCIAC), resistance and amperage scales additional features such as temperature, duty cycle and
engine RPM etc. are often incorporated in dedicated test meters for automobile applications.
Using multi-meters
Voltage checking - Fig. 3, Fig. 4, Fig. 5
---
81
-
Fig. 6
Set the meter to VOLTAGE.
If applicable, set the meter to the correct scale e.g.
ACIDC, VImV etc. (most modern meters are selfranging).
Connect the black test lead to the negative terminal
being tested.
Observe the conditions of the test, e.g. ignition ON etc.
Connect the red test lead to the positive terminal being
tested.
Read and record the value displayed.
Measurement of voltage drop through cables and
components can be a useful diagnostic tool, as any
abnormal condition will have an effect on the operation
of the circuit(s) and components involved.
The multi-meter should be set to measure milli-volts
and the circuit should be in its normal operating mode
e.g. all multi-plugs connected and current flowing.
Maximum voltage drop should not exceed the following values:
Control module harness wire - 200 mV
Switch - 300 mV
Earth connection - 100 mV
Sensor connection - 50 mV
Fig. 3
Checking voltage with multi-meter
Fig. 4
Fig. 5
Checking supply voltage - harness multi-plug
disconnected
Checking signal voltage between wires -
harness multi-plug connected