Based on the comments below - I wonder a polluted highway/slow traffic can trigger it - see below.
Note: Believe it happened many years ago - say 5 on my 2000 Acura Integra. Not sure what the code was but it was reset by the m/c - now it on a slow freeway - I recall there was a truck in front of me smelled bad - so I changed vent to circulation - wonder that pollution might have triggered it in my car. I recently did complete timing belt:
" The most “common cause” of the “check engine” light is the Exhaust Gas Recirculation
(E.G.R.) valve on most Asian vehicles. Although
it is sometimes quite disconcerting to have the
light come on it is usually not harmful to the engine or it’s performance. The E.G.R. valve is
exposed to high temperatures and it can get
“carbon fouled” easily and therefore send a
signal to the Electronic Control Module (E.C.M.)
that there may be a problem (not necessarily
a significant one)."
Source: http://forums.edmunds.com/discussion/770/general/x/check-engine-light
Without the code it’s a pure guess, despite what that quote says.
I seriously doubt following a belching truck will set a CEL. The diagnostic system requires the problem to repeat itself multiple times within a certain drive cycle time frame to determine if to set a trouble code and turn on the CEL.
" The most “common cause” of the “check engine” light is the Exhaust Gas Recirculation
(E.G.R.) valve on most Asian vehicles. Although
it is sometimes quite disconcerting to have the
light come on it is usually not harmful to the engine or it’s performance. The E.G.R. valve is
exposed to high temperatures and it can get
"carbon fouled" easily and therefore send a
signal to the Electronic Control Module (E.C.M.)
that there may be a problem (not necessarily
a significant one)."
IMHO this is BS on so many levels that I don’t know where to begin.
High temperatures do not cause carbon fouling. Carbon in the exhaust does. And the reason for the carbon is often elsewhere, like rich operation or poor combustion. Those can further be traced to defective sensors, bad sparkplugs, and/or other root causes.
EVAP system problems causing CEL codes is not unique to Asian cars. Far from it. It’s an equal-opportunity problem.
Assuming that a CEL is usually not harmful can be, and has for many people been, a very expensive assumption. There are large lists of possible causes for a CEL that can cause damage if not addressed.
I recommend against basing any assumptions on the quoted statements.
Your air filtration system is perfectly and totally capable of keeping even the dirtiest, carbon filled truck exhaust from damaging your engine to way, way below levels that the engine can harmlessly process in combustion. It might leave a terrible smell in your nostrils, but your engine is very capable of dealing with it. Your nose is sensitive to a few parts-per-million particles of contamination in the air, your engine is not.
Actually, if anything, high temps would tend to keep carbon at bay. Low temps/short trips/poor quality fuel are the main reasons engines carbon up.
As Busted Knuckles said, it takes several occurrences of an “event” to set a code and turn on the MIL or check engine light. Unless you’re driving through an area where the air is bad enough to asphyxiate you, it’s unlikely your engine will even notice. What do you think the “air” is like in your cylinders during combustion? The only air monitoring done “upstream” to the cylinders is air density or pressure, depending on the system design, and incoming air temperature. Oxygen content is monitored downstream (in the exhaust) The only things monitored by the EGR system are flow and the valve’s position. (both to verify whether it’s actually working)
If your check engine light is coming on, the cause is not anything in front of you, though a car that needs maintenance may be more susceptible to triggering a fault code in certain conditions, such as extended idling, weather conditions, or various driving modes than a healthy vehicle.
You need to discard speculation and get some facts. Get your own OBD-II code reader so you can plug-in and view and document the fault.
Besides everyone who works on cars knows the number one cause for engine light is an evap problem such as a leaking or improperly installed fuel cap.
I dismissed the idea as soon as I saw the word “edmunds.” They create “news” just like the National Enquirer.
It is Acura Integra 2000 Auto with 100k miles.
I had it over 10yrs - changed tranny fluid with Acura as per the book.
Car runs fine. But these are the codes:
P700 - transmission control system malfunction
740 - torque control converter clutch circuit malfunction
Once before, about 4-5yrs ago it happened - not sure what the codes were - it was just reset. It shifts gears fine even now. What is going on?
Mechanic asked me to reset the code and if the CEL came on, then it needs to be repaired. So I did that - have not driven it but started the engine - so far good. Will report after a few days.
I was pulling a loaded U-Haul trailer with my 1990 Ford Aerostar on a busy interstate when the traffic ground to a stop due to road construction. For the next hour, the traffic inched along at less than 10 miles per hour. My check engine light came on. After we got through the construction and back up to highway speed, the light went off and stayed off. I asked a mechanic about it and he thought perhaps all the pollution from the exhaust from all the vehicles in the traffic may have triggered the light. I never had that problem happen again in the next five years I owned the Aerostar. I’ve wondered about my mechanic’s assessment since that time. If true, I am not sure the air we were breathing on the interstate was all that good for us.
@Triedaq - yours went off automatically. Mine didn’t and pointed to Tranny. I drove 20miles and it had not come on yet.
M/c at PepBoy thought that in traffic, if my car was constantly accelerating and decelerating - then the controller might have got lost in tracking the gears resulting in the code. He thought it needs repairs. Let see if the light comes on. I am due for Tranny fluid change in 2 months.
Done over 50 miles no issues.
Referring to the link below, can the CEL came on due to:
“Minimal decrease in fuel economy, …”
Read more at: http://www.obd-codes.com/p0740
Copyright © OBD-Codes.com
<blockquote>Referring to the link below, can the CEL came on due to:
“Minimal decrease in fuel economy, …”
Actually no, It came on due to : Torque Converter Clutch Circuit Malfunction.
Minimal decrease in fuel economy,… is a symptom not a cause.
Some of the causes are:
Wiring harness to transmission damaged, loose connection, open or shorted circuit Torque converter clutch (TCC) solenoid Transmission control module (TCM)
Read more at: P0740 Torque Converter Clutch Circuit Malfunction DTC
Copyright © OBD-Codes.com
M/C at Pepboy… Yes, that sounds about as intelligent as anything else you hear at Pepboys. I only go there when they have a great sale on oil.
I have done over 259 miles without the CEL coming on. So that is a good news.
Thanks for the note. I will take it to a private Tranny m.c to check it out.