Don't you just hate that little light...

Well, one week and 400 miles into my "new" car ('02 Blazer), there goes the check engine light, and a slight intermittent shudder at the idle.

Luckily it's well within the token 2 month/2,000 mi warranty, so of course I intend to pursue that, but if it turns out that I've been screwed, I hardly trust their mechanic to tell me so...

Which brings me to my question, since this thing is 10 years younger than any other car I've ever laid hands on...

Can you still read ECM codes on a Chevy by finding the two terminals near the fuse pannel and bridging them to read the blips on the check engine light, or do you need one of those pricey little trouble shooting computers that I've heard complained about?

I suppose it'll tell me that when I buy the manual I'll need to find out what the trouble codes are, but no sense buying the manual if I can't do that.

The best tool you can buy for your vehicle:

www.autoenginuity.com...

It's not cheap, but neither is being "had" by a mechanic.

A scan tool like this allows you to scan for codes, clear codes (get rid of the "check engine light") and run diagnostics.

A worthwhile investment IMO.

I read the other day that if the check engine light comes on and nothing seriously seems to be wrong it is often the seal around the gas cap. Once you lose pressure in the tank the light comes on.

It may not help one bit but I thought i'd toss that out there. Hell, it might just work.

The "money light" LOL.

Doesn't matter, you're going to owe someone 1,100 dollars.
Just kidding really!!

Gas cap, even an incorreclty positioned Oil dipstick can cause it ( i did not know that)..
Here is a website with a Car "fessing up"Check Engine

Well, I went and bought the manual before I noticed the replies here... no big deal because I'm sure I'll eventually need it.

And unfortunately you're right... don't bridge anything. I really miss the OBD-I (I've never owned anything newer than '94 before, so I've always been able to just run a wire between two terminals and count the blinks of the check engine light- I wasn't even entirely certain that this was impossible on OBD-II until I checked into it).

I'll have to invest in the scanner soon- 250 bucks seems worth it to keep the gas mileage good. Preventing the loss of 1 MPG to a bad sensor or other problem would save me 6% on fuel if I've done the math right, meaning that the scanner will pay for itself within 2,000 miles of the first problem that costs me gas mileage.

To my delight though, the dealership isn't giving me any flak about actually using the 2,000 mile token warranty that they offer (I just naturally assumed that there'd be fine print specifying that it only covers a piston protruding through my hood), so this one is on them, giving me a little time before I have to spend 250 bucks (a small fortune to a college student who has elected not to take student loans until transfering to a 4 year school).

Thanks for the replies.

(edit to add- I've lost 2mpg it appears, and I'm still noticing a slight shake at the idle, so I doubt gas cap and dip stick. Timing came to mind, but someone a little more experienced than me says that while that makes sense for my usual cars, it seems unlikely for a newer one.)

[edit on 9-1-2007 by The Vagabond]

This may be knowledge so common it's irrelevant, but I'll throw it out there anyway.

Many auto repair places will charge you a "diagnostic fee" of $75 (or more) to hook your car up to their computer and tell you why the light is on.

Auto Zone locations (and some other parts places I believe) will hook your car up and give you that info for free.

If you aren't near an Auto Zone, you might check with some other auto parts places locally. Could save you some trouble and $$.

Personally, I'm a big fan of Auto Zone.

Thank You for the AutoZone plug..........

pep boys has a mini obd2 scanner you can buy for $40 that will tell you what set the light off.

Not specifically related to your problem, but you should consider making friends with one of the technicians.

Once you're buddies with them, many techs will work for cheap on their own time. Cheap = beer. Most dealerships have shop nights once a month where techs can work on their own cars and that of their 'families'.

A case of beer is a small price to pay to get hooked up to the diagnostic machines.

yeahright
Auto Zone locations (and some other parts places I believe) will hook your car up and give you that info for free.

I feel this can't be stressed enough.

Auto Zone locations will hook your car up to the diagnostic scanner and give you that info for free.
Auto Zone locations will hook your car up to the diagnostic scanner and give you that info for free.
Auto Zone locations will hook your car up to the diagnostic scanner and give you that info for free.
[3X for good measure]

Fair Warning
The code does not specify what the problem is. Only which sensor is indicating a problem. You have to use your brain and think it through to figure out what would cause that particular sensor to give that reading.

For example; it could indicate that you have a misfire on cylinder x. Do you go inside and buy a spark plug or injector? NO. First, ask yourself what would cause the misfire? A bad injector, plug wire, defective ignition coil, a clogged or dead fuel injector, loss of compression due to a leaky exhaust valve, leaky head gasket, worn cam lobe, etc.

Lots of people go spend good money to change out parts (cough *oxygen sensor* cough) because the code said there was a problem. It seems to have fixed the problem because the check engine light went out. In reality, they accidentally cleared the codes by disconnecting the battery during repairs, which shuts of the check engine light, (for a while). And they still have another problem.

My point is that in most cases the code has no meaning except as a pointer to guide you to the problem area, so you can continue standard troubleshooting.

As for the rough idle, it may be as simple as a bad injector, or perhaps this:

TSB #030604041 -- POOR ENGINE PERFORMANCE - MISFIRE, ROUGH IDLE, SERVICE ENGINE SOON/CHECK ENGINE LIGHT ILLUMINATED, DIAGNOSTIC TROUBLE CODE (DTC) P0300 SET. *TT (NHTSA ID #10004377, FEBRUARY 01 2005)

Chevy Technical Service Bulletin # 030604041

The above is a TSB of a part on the 2002 Chevy Blazer. The Most shops wont volunteer the info, or dont know about it. But if you take it to AutoZone, and get a code P0300, printout the TSB, and take it to the Chevy dealer. If it meets the following conditions, they will fix it free:

Your vehicle is under warranty;

Your service advisor and/or technicians are able to confirm that the problem exists.

[shrugs] Worth looking into anyway, right?

PS
Code P0300 indicates a misfire, but it does not tell you what is causing the misfire.


Diagnostic Code List

other Chevy 2002 TSB's

More about TSB's

Search for vehicle TSB's, Recalls, and complaints

[edit on 1/12/07 by makeitso]

If you live in California,Auto Zone can no longer do a code scan on your car,another way we are screwed,evidently it stops the mechanics from ripping you off for using the same scan tool,you can buy one for around 70 bucks,worthwhile investment if you work on your own car

Well, I've been dealing with this problem intermitently for a year and a half, so the thread is back.

Go figure, the dealer blamed the gas cap and replaced it, and cleared the trouble codes while they were at it, getting rid of the light. It ran fine for a while (the shudder was very mild and went away not long after the gas cap was replaced) then the shudder came back much much worse about 6 to 8 months ago.

I went to autozone, checked the codes, and found a random misfire on multiple cylinders. I filled it up and put in some techron, then limped it up the freeway to my dad's house to change the plugs, and the distributor cap and rotor. The techron and full gas tank fixed the problem before I got to my dad's, (it had gotten to the point where i couldn't put my foot into it or idle it without stalling, and it went away completely) but I changed the plugs, cap, and rotor anyway.

Recently phase III has started. When low on gas (but before the low fuel light comes on) it is extremely difficult to start the engine. I often have to put it on a battery charger to turn it over enough to start it. Filling the gas tank always fixes the problem. A new fuel filter didn't change anything.

So it seems like a slam dunk to me that I've got some crap in the bottom of my gas tank and probably on my fuel injectors too.

Cleaning the injectors is no problem. But the gas tank is outside my experience. Am I going to have to drop the tank to check this out, or is there an easier to access point somewhere that would definitely trap contaminants and let me know whether or not there is a problem in the tank?

reply to post by The Vagabond



Hey Vag. A common problem with the V6 vortec (I'm assuming that is what you have) is leaky injectors with the multiport injection. This will eventually give you codes and make for very hard starting (will take a long time to crank over enough to fire). Simply, the injectors get worn and leakdown causing the fuel system a while to pressurize enough to provide the right mixture for starting. This also causes a poor mixture at idle which will cause intermittent misfires.

You might be able to alleviate this somewhat by turning the ignition key switch to on several times before actual cranking to allow the fuel pump to pressurize the system, then crank it to start.

However, you would really need to buy a new set of injectors, which would probably be around $300 just for the parts.

Hope that helps.

Thanks for the tip. New injectors just aren't in the budget right now. First item on the agenda is to clean them up and hope they are only obstructed.

If the injectors are leaking, I should be able to turn the key off and on repeatedly and then smell it flooding for a quick test, correct?

Originally posted by The Vagabond
Thanks for the tip. New injectors just aren't in the budget right now. First item on the agenda is to clean them up and hope they are only obstructed.

If the injectors are leaking, I should be able to turn the key off and on repeatedly and then smell it flooding for a quick test, correct?

That sounds possible if you had some way to stick your nose in there. The whole plenum is sealed, but if you did that without cranking and opened up the hose connected to the throttle bore you should be able to smell gas if it were leaky.

They make a nifty tool for injector cleaning that attaches to the Schrader Valve somewhere on the pressure side of the fuel system on the line. Any place that sells this would have cleaner as well. It's more effective than putting injector cleaner in your tank. It has a line with a canister and you put the cleaner in the canister and run it dry. It may improve the injectors some, but if they are worn out, there isn't going to be much else to do but replace them.





[edit on 7-12-2008 by ben91069]

Thanks for the tip. I'll let you know how it plays out when I finally get it done. (I am the master procrastinator, as evidenced by the start date of this thread).

i feel for ya man. lotsa trouble dealing with auto's sometimes.

this is just my opinion but i would never take my car to autozone to have them read the codes. i don't even let em put wiper blades on

I've never had a problem with autozone helping me read the trouble codes. Mostly I just do it because having one of them come out to the parkinglot with me is a lot easier than leaving a 200 dollar deposit for the reader. Having seen the test autozone gives applicants, I wouldn't trust them to be the final word on something tricky, but for most intents and purposes, if you also have a decent idea of what you're up to, there's not too much danger of you and them together screwing up too badly.

my car threw a code yesterday while i was driving. car was stuttering and i had to pop in it neutral at a stop light to keep it from stalling. i got to where i was going and shut it off. did what i had to do and when i got back in everything was fine. no light and no running problems.

must not have been a hard code