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Check Engine Light Question and Answers
This category contains featured questions as examples and relate to
most vehicles.
Question: 1999 Ford Expedition.
We tested the SRS. The malfunction Indicator
blinked Code 52. Checking DERM we found some
water at that area and we thought this the cause
of the fault. After replacing DERM, the vehicle
operated without trouble - but only for two
weeks. After this period, our client came again
for service: MIL of SRS blinked trouble Code 12.
The fuse of the system has blown. Fitting in a
new fuse the MIL blinked Code 52 again. We
didn't find any trouble as before. Shall we
replace DERM again? What would be the cause of
the repeated fault? Can you give us some idea?
(Unfortunately, we haven't DRB for this model
because there are only a dozen Expeditions in
our country) Awaiting for your reply - Regards
from Hungary, Budapest
Answer: You should replace
the DERM again. However, before you do, check
the wiring looms in the engine compartment for
damage or bad connections. Also, check the
ground connections for high resistance. Either a
shorted or a bad connection will overload the 12
volts causing the failure you described.
Question: 1998
Chevy/Spectrum 4 cyl mileage: 86,000. Same as
Isuzu I-Mark Have 1986 Chevy Spectrum, 4 cyl,
AT-AC, 86k miles. Local service centers stumped.
Been checking off and on since 12/18/00. We have
emissions requirements here and vehicle was
waived two years ago. Would not pass test and
diagnosis unknown. State will not allow a waiver
two periods in a row. In last year, had
radiator, heater core, plugs, wires,
distributor, cap, rotor, fuel & air filter, O2
sensor all replaced. Vehicle scoped and no
answer to symptom of wanting to shut off while
idling at a stop. Engine seems to choke & tries
to shut off. When given a little gas, it revs up
nice and smooth. Only other symptoms are an
intermittently blinking check engine light that
shows no trouble code and engine runs cool, even
though thermostat replaced with 195-degree unit.
Was told to go buy another car that passes
emissions.
Answer: Your problem may be
an idle speed control motor or possibly a
partially plugged
catalytic converter. The blinking check
engine light would indicate a stored fault code.
Retrieving the codes of your make and model of
car is difficult.
Question: 1998 Cadillac
Eldorado mileage: 82,000. Recent engine problem
said to be MAYBE a MAP sensor as car stalls with
Fuel Rich Mixture and gives a Code of 21.
Changed TPS and idling improved but erratic
(sometimes) stall occurs proceeded by "Check
Engine Light"! Spent thousands of dollars on
this engine since day #1 - has NEVER run
correctly - believe it to be and have
spent lots more restoring car as my wife loves
it! #1 Do you believe it is as simple as MAP
sensor (current crisis)? And #2 where on earth
can I buy one? Have tried! #3 Can I get this
lemon engine to EVER run right? Can a speed shop
do it? Tell me - please! Can you explain why
this year's engine has been such a problem?
Cadillac was NEVER able to make it run smoothly
and correctly! Remedies?
Answer: The coolant
temperature sensors were not the best. The same
type of sensor is used for the air temperature.
Replacing both of them at the same time is a
good practice. Also, check the
fuel pressure regulator. We do not believe
the MAP sensor is your problem.
Question: 1999 Mustang Cobra
mileage: 87,000. I have been going back and forth
with this Ford dealer who couldn't seem to
install my clutch properly. After three
attempts, the second two at no charge to me, the
clutch seems to be working fine and the car
seems to run ok. However, soon after I picked up
my car the third time and drove to my
destination. My check engine light comes on and
stays on. When I turn my car off and back on it
goes off, but will come back on and stay after
driving some variable amount of time. Does a
clutch replacement require any interaction with
sensors or any component that affects the
computers' readings that may cause the check
engine light to come on?
Answer: Your car is equipped
with four
oxygen sensors that are close to the
transmission. If one of them was inadvertently
not reconnected, it will light the check engine
light.
Question: 1993 Chevy c10
pickup 2wd mileage: 272,000. When I am driving on
a road with a lot of hills or curves sometimes
my service engine light comes on It seems to
only effect the brake system as there is no
noticeable engine change, except when I shut the
motor off it will keep running for a few
seconds. After about 5 minutes, I can restart
with no problems. I have also had the light come
on at highway speeds with the same effect. I
took it to my mech. and he tried to use his
analyzer on it but it would not compute. The
message came back no connection possible. He
said he would have to replace the computer to
find out what the problem was. This seems to be
an expensive way to find the problem.
Answer:
When your car is in use several
electronic components are used. Making this particular repair is one
of the most dreaded. Your problem could be from your ignition switch
to a fuel
pump, about 15 different things can cause this condition.
Question: 1989 Chevy
Corvette mileage: 67,000. I got a code 34 on my
computer, went in had another MAF put in, car
ran fine for 3 days with no codes. Suddenly code
34 is back...what could cause this.
Answer: The
catalytic converter may be the cause of the
failure code for the mass airflow sensor (MAF).
If the converter is partially plugged, it backs
up the exhaust, which affects intake manifold
vacuum. The airflow into the engine is then
affected resulting in your code 34.
Question:
1996 Honda Civic mileage: 155,000. I bought a
liquid bottle called "fuel up"(for fuel
system/anti-rust cleaner) pour half of the
bottle in the gas tank (full), as recommended on
the instructions. Next day I drove my car for
about 15 minutes and the "check engine" light
came up, I stepped on the gas pedal and the car
turned off, I started the car again and it
turned on ok, and the check engine light went
off. I would like to know if it was the fuel
system cleaner I bought or something wrong with
the car. Please help. Thank you.
Answer:
There is a chance that having it in the fuel
system may have caused a malfunction in the
oxygen sensor lighting your check engine
light.
Question:
1999 Nissan Sentra mileage: 121,000. The "Check
Engine Soon" light came on the other night, but
the car seems to run fine. One of my friends
says it's probably just that I need more
anti-freeze or coolant. Is this right? This
is Michigan and its about 10 degrees F during
the night.Answer:
The “check engine” light will “light” when there is a malfunction in the engine
management system. The fault code is then stored in the computer.
The computer must be scanned to retrieve these stored faults to pinpoint the
malfunctioning component.
Question:
1997 Chevy Lumina 3.8L mileage: 98,520. I have
been getting a service engine soon light for
some time and haven't been able to find a cheap
code scanner for this vehicle. I bought a Hayes
computer code trouble-shooting manual and it
tells me to put a jumper in the A and B slots on
the ALDL to ground the diagnostic terminal. The
only problem with this is that there is nothing
in the B slot; it just goes all the way through
the back of the socket. This ALDL has only 3
terminals being used in it. There is one in the
A position and one below it. According to the
book there should be a B terminal right next to
the A. This car is OBD1 certified and I guess
what I need to know is what is the proper why to
jumper out the ALDL to retrieve the codes or do
I have to take it to a service shop to have it
done on a diagnostic machine. I would greatly
appreciate your help in this matter.
Answer:
Your car cannot be jumped between the A and B
slots to read the codes. 1993 was the last year
where this could be done. Your car has to be
scanned with an OBD II scanner.
Question:
1997 Saturn SL2 mileage: 118,000. If I change
the O2 sensor (on the exhaust manifold), how can
I re-set the diagnostic computer codes so the
"Check Engine" light will go off? Also, the
J.C. Whitney catalog lists a universal
'one-wire' oxygen sensor; will this work on my
Saturn? Thanks!Answer:
The check engine light on your car must be reset
with a computer scanner. In addition, if your
car is equipped with a one-wire oxygen sensor,
then the one-wire sensor should work. However,
your car has a four-wire sensor.
Question:
1992 Hyundai Accent mileage: 155,000. Ok my
Hyundai Excel was not treated as well as it
should have been. I believe the one of the
cylinder piston skirts cracked. It was time
for a new engine. My mates and I pulled out the
old one. Placed in a reconditioned engine...
much better. But. Initially the timing was
retarded too far and therefore the engine
backfired. I drove about 100 miles with the
engine like this. I got my hands on a timing
light and was just about to tune it when the
CHECK ENGINE light came on. My manual says
that this indicates a problem with the exhaust
system. I cannot detect any such problem and
the engine appears to be working perfectly (Once
I fixed the timing). What do I need to fix?
Did the backfiring just fry some environmental
circuit? I have heard third hand of an Excel
having the same light turn on, nothing wrong
with it. Kept on going for years. Any help
would be appreciated.
Answer:
The light can be extinguished and fault codes
cleared by disconnecting the battery for several
minutes. If there is a malfunctioning sensor or
switch, it will relight the light. The “check
engine” light will “light” when there is a
malfunction in the engine management system.
The fault code is then stored in the computer.
The computer must be scanned to retrieve these
stored faults to pinpoint the malfunctioning
component.
Question:
1998 Chevy 1500 Truck 4x4. I just bought a used
Chevy 1500 4x4. I was wondering if there is one
of those levers or buttons that you have to push
in to turn off the service engine light after
you have changed the oil. If you know where
this magical button is could you email me back,
thanks a lot.Answer: There is no magic button
for the service engine light. If there is a
malfunctioning sensor or switch, it will relight
the light. This is good you will know for sure
that something is wrong. The “check engine”
light will “light” when there is a malfunction
in the engine management system. The fault code
is then stored in the computer. The computer
must be scanned to retrieve these stored faults
to pinpoint the malfunctioning component.
Question:
1994 Buick Regal mileage: 105,000. The check
engine light comes one frequently but with no
certain pattern. We asked our technician about
this indicating there was no change in
"functionality" of the car when the light comes
on and he said not to worry about it. I have
also been told this is a common trait with this
vehicle. What is your professional opinion?
Answer:
When your car is in use several
electronic components are used. Making this particular repair is one
of the most dreaded. Your problem could be from your ignition switch
to a fuel
pump, about 15 different things can cause this condition.
Question:
1990 Buick Electra Park Ave. mileage: 124,000.
Car runs great. Speedometer does not always
work. When it does not work and I am climbing a
hill the "check Engine" light comes on. As soon
as the speedometer starts to move again, the
light goes off. Sometimes the light will stay
on for 30 minutes, but when the speedometer
moves, it goes out. Immediately car runs
great. If I am going with traffic say 55 - 60
the speedometer reads 25 or so (sorta got to be
careful about getting out at that speed Eh?) I
get a code 24 from flashes on dashboard when
asking computer about "check engine" deal.
Problem is: the guys at the GM dealer say that
there is no VSS on that year and model. And
besides when I do find it, if I do have one on
the car. Is it behind the speedometer or on
transmission somewhere? Thanks for any help.
Answer:
Your problem may be caused by the cruise
control transducer. The speedometer cable from
the transmission goes into the transducer and
back out to the speedometer. It is more likely
than not that the transducer is causing the
problems you are experiencing. The vehicle
speed sensor should be located in the rear of
the transmission.
Question:
2001 Ford Escort 1.9l Fi mileage: 75,000. I am
an ex GM mechanic, is there anyway to read and
clear fault codes on this vehicle without a
scanner?
Answer:
A scanner is necessary in order to read and
clear the codes on late model Fords.
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