yellow check engine light

Yesterday my husbands was driving our car to and from work about 20 miles
into the trip the yellow check engine light came on whatcould that
possibly mean. Its a 1994 civic dx just turned to 130,000 running good
also.

 

So far all we know is that the engine computer (ECU) has decided it isn't
getting what it wants to see from something that will affect the engine's
emissions. The next step depends on what codes the ECU has stored. In your
1994 you can find that out yourself. Instructions are in
http://www.iequus.com/assets/manuals/3173_ICCR_E_14JAN03.pdf with the
procedure for your '94 Civic starting on page 18 of the PDF. Where the
instructions say to insert a "Code Reader" it means to connect the two
terminals in the plug with a wire. (I bought the book with the "Code
Readers" for all the cars listed - Toyota and Honda are little jumper tools
while the Nissan is a plastic screwdriver - for $35. D'oh!) Instructions for
interpreting the codes follows on pages through 25... you will probably want
to print them out so you can take them to the car. The same pages also have
instructions for clearing the codes, which will turn off the yellow light if
condition was transient or after fixing the cause.

I know it would be easier to just reset the codes and see if it is okay, but
it really is important to know why it is disturbing you. Whatever it is, as
long as the car drives the same it won't hurt it to drive in town or gently
on the freeway. There is (at this point) a risk that the mixture could be
very rich, which could damage your catalytic converter through overheating
if pushed hard for more than a moment. Once you determine fuel consumption
is fairly normal that restriction is lifted. The light is there to warn the
driver of emission related failures that would otherwise not be noticed,
although in later years even transmission codes have been piggybacked onto
it. In fact, on 1996 and later systems even a loose gas cap will light the
light, and on those models a special electronic tool is needed to read the
codes and reset them. That's progress?

Mike

 

It means a sensor has either failed or returned an invalid signal to the
ECU.

You need to get the code read, like Mike Pardee says. A paper clip can be
your "wire" for jumping the terminals of the Service Check connector.

The usual procedure here is to make note of the code, then clear it from
the ECU according to the steps in the iequus document. If the Check Engine
light comes on again later, see if the code is the same. If it is, report
back here and somebody can point you in the right direction.

 

go the car checked and fixed it was the heated o2 sensor. thanks guys for
being right.even though i was sticker shocked