Car Forum World

How do you read the check engine codes on the 1990 Volvo 740?
The engine computer looks kinda like a lego, how do you read the fault code something to do with the button and red light ? Thanks.

Your Volvo comes with the 1st generation OBD
on board diagnostic feature. So there is not any
aftermarket code reader devices for it. But I can tell
you how to retrieve any codes that are stored in your
Volvo's ECM electronic control module . there's a
black diagnostic test box located in the engine
compartment near the left strut tower. Remover the
cover, if it is still there, put the pin thats
attached to the wire into socket #2. Turn engine key
to the on position. On that box there is a button, push
down on button for no more than two three seconds then
release it. If there aren't codes stored in it the red
led light will flash three times with a pause between each
number. Ex. one 1 1. If code two three two is stored in for
example it could blink two times..pause..blink 3
times..pause ..2 times. If there are more than one code
then you could have to push button for each code
stored. you will no there aren't more codes stored when
the 1st code that has been retrieved repeats itself.
Insert pin in socket #6 to retrieve the ignition in
the same manner mentioned above. you may be able to probably
Google the codes for interpretation of each code. To
clear codes you have to read all codes then hold push
button down for six seconds. Use a clock or stop watch
to count seconds because it is nearly 99.9% efficient.
The led should light up hard. Then hold it down for
another six secs. Light should go out. you will know when
you erased codes when the led flashes the code one 1 1.
Good luck.

VOLVO SERVICE consultant AND 740 OWNER

If it is not listed in your car manuel, you may want to call the car dealer,they can tell you. good luck.

if you do not get an answer you like go to autozone they'll let you look through their manuals.