Expo LRV AWD L4-2350cc 2.4L SOHC 16 Valve (1993)
Engine Control Module: Technical Service Bulletins
Engine Controls - Never Use a Test Light To Check an ECM
NO.
TSB-92-00-003
DATE
August, 1992
MODEL
All Models, All Years
SUBJECT:
ECU CIRCUIT TESTING PRECAUTIONS
PURPOSE
This bulletin is issued to remind technicians NOT to use a test light when checking computer controlled circuits. A Digital Volt-Ohm Meter (DVOM)
should be used whenever checking the voltage in any computer circuit. NEVER USE A TEST LIGHT TO CHECK ANY COMPUTER CIRCUIT.
DETAILS
Electronic Control Units (ECU) returned for failure analysis contain burnt transistors. This type of transistor damage is typically caused by excessive
current demands. Research has proven that ECU damage can and will occur during diagnosis by using a test light to check for voltage in computer
circuits. A test light bulb, in order to light, will draw a considerable amount of current from the circuit being tested. In some cases, high current flow
overloads solid state components causing damage.
A Digital Volt-Ohm Meter is the preferred measurement device for checking computer system voltages. Of limited alternate use, an Light Emitting
Diode (L.E.D.) tester (logic probe), or lab-type oscilloscope can be used during some tests. These devices draw only a very small amount of current from
the tested circuit.
NEVER USE A TEST LIGHT TO CHECK COMPUTER CIRCUITS.
