Check engine light from nowhere?

[Proto_Man]

I drove my msp down to rehobeth today, and it was running perfect, no problems whatsoever. Then all the sudden as I leave the grocery store stopped at an intersection, I notice that the check engine light is on. There were no odd noises, no changes at all in the car. I drove it 15 minutes back home and had no problems, listening for anything at all. When I drove it home I checked everything I could and found nothing wrong. Tommorrow I'm going to autozone to get a read because Im assuming the problem is small.. and electrical. My msp is completley 100% stock, so its sureley no problem due to a stupid mistake on my part. I know my description is vauge, but I figure someone might have a similar problem? Any feedback would be GREATLY appreciated.

[Sveivo]

I drove my msp down to rehobeth today, and it was running perfect, no problems whatsoever. Then all the sudden as I leave the grocery store stopped at an intersection, I notice that the check engine light is on. There were no odd noises, no changes at all in the car. I drove it 15 minutes back home and had no problems, listening for anything at all. When I drove it home I checked everything I could and found nothing wrong. Tommorrow I'm going to autozone to get a read because Im assuming the problem is small.. and electrical. My msp is completley 100% stock, so its sureley no problem due to a stupid mistake on my part. I know my description is vauge, but I figure someone might have a similar problem? Any feedback would be GREATLY appreciated.

Loose gas cap maybe? (coffee)

[protegeV]

Loose gas cap maybe? (coffee)sounds like it. could be a LOT of things. 9 times out of 10 when the CEL comes on in most modern cars you dont notice anything wrong with the car.

[Proto_Man]

I turned the gas cap till it clicked, and started it.. still got that pesky check engine light. Any more ideas?

[protegeV]

depending on your car you'll have to drive the car for several drive cycles until the test runs itself again and passes. If its an evap leak you'll have to drive the car till the fumes in the tank heat up and cause a rise in pressure. Then once you shut the car off it'll look for the rate of drop in pressure as the tank cools. if it drop too fast you've got a leak. I forgot to tighten the gas cap on my neon and it took about 60 miles and 8 drive cycles before it turned off.

[Proto_Man]

What a drag! Well im 99% sure I put it on right the first time.. but will the diagnostic system recognize that as the problem if it is? I really don't feel right driving it much when that light is on.. idk, guess we'll find out tommorow. I'll let you guys know how it turns out. Fingers crossed.

[protegeV]

good rule of thumb is that its okay to drive the car as long as the light isnt flashing. If the CEL is flashing there is a catalyst damaging problem, likely a multiple cylinder misfire.

[Proto_Man]

Oh.. well.. wouldn't want that. Cylinder misfire is generally frowned upon.. no I don't like that one bit. Thanks for the help! :D

[exNeon]

when the code is read, have the guy clear it and see if it comes back.
or unplug the battery and drain the electrical and see if it comes back.

[protegeV]

if he's having the code read no need to worry about disconnecting the battery and losing your radio presets.

[Proto_Man]

So I went to Autozone, and the code came up as a PO171.. the paper reads as follows:

Troubleshooting P0171
OEM Brand: OBDII

"The PCM has determined that during testing, the fuel system for bank 1 was too lean."


Troubleshooting P0171
OEM Brand: Domestic

Definition
Fuel trim band one condition

Explination
The powertrain control module uses the oxegen sensor to calculate the air/fuel ratio of the engine. The computer has recognized a rich or lean condition on one engine bank only.

Probable Causes
1-If bank one and two codes set together suspect fuel pressure of mass air flow sensor
2-o2 sensor defective
3-Ignition Misfire - repair
4-Fuel Injector problem

:(

[protegeV]

ah, a lean code. tons of different things that could be. Your car is a four cylinder, so no need about a P0174(lean bank 2).

Could be an unmetered air leak. Air getting into the engine somewhere between the after the MAF...Could be a bad 02, bad MAF, low fuel pressure, exhaust leak.
Definitely not as simple as an evap code, but not earth shattering. Usually if your fuel trims go above 20% this code will set.

[Proto_Man]

Well if it was a bad 02, or an exhaust leak, wouldnt it be running too rich? I'm going to check the connections from the turbo to the intake manifold, and the connections from the MAF down to the intake manifold.. just to make sure all the connections are tight, then take off the positive side of the battery.. let it sit for 10 mins and plug it in.. hopefully that fixes my problem. A new fuel filter is also probably due for replacement by now milage wise.. and that could help too. I'll keep you posted, and thanks for the advice.

[Mazda_Tech]

po171 code is prob a vac leak, check all your hoses and see if any are cracked, if so replace it.

But i bet you need a new wastegate actuator. How many miles on your car?

[protegeV]

Well if it was a bad 02, or an exhaust leak, wouldnt it be running too rich? I'm going to check the connections from the turbo to the intake manifold, and the connections from the MAF down to the intake manifold.. just to make sure all the connections are tight, then take off the positive side of the battery.. let it sit for 10 mins and plug it in.. hopefully that fixes my problem. A new fuel filter is also probably due for replacement by now milage wise.. and that could help too. I'll keep you posted, and thanks for the advice.nope...if the o2 sensor is gett what they call "lazy" and slows down in the lean area...above 450mv...then you may get a lean code. As well, if there is an exhaust leak which is causing fresh air to get sucked into the exhaust system before the o2 you can get a lean code...
but yeah, its probably a vacuum leak, most likely.

[Proto_Man]

po171 code is prob a vac leak, check all your hoses and see if any are cracked, if so replace it.

But i bet you need a new wastegate actuator. How many miles on your car?


only 56k

[protegeV]

depending on how you drive it I wouldn't say ONLY 56K...I know the way I drove mine it probably felt like it had 56K on it when it hit 25K...lol

[dragtillidie]

if u have a boost gauge it should sit around -19 to -22 at idle if im not mistaken...if its less then go find ur leak

[protegeV]

if u have a boost gauge it should sit around -19 to -22 at idle if im not mistaken...if its less then go find ur leak
you mean if its more...as in higher...closer to 0?

[greasemonkey524]

Yeah. If it's between 19 to 0 you have a leak somewhere.

[MSP_4_CODY]

yeah or it could be nothing, clear the code out, drive it and if it comes back then you worry. it could be caused be crappy gas even, so clear it and let us know!

[Proto_Man]

Found the problem and fixed it! Turns out it was a simple vacuum leak! I was worried for a while.. thanks for all the help guys!

[MSP_4_CODY]

oh cool! high five

[greasemonkey524]

Glad to hear you found it!

[Proto_Man]

*virtual high five* its never that easy for me.. ive got a 1971 Monte Carlo... im used to the mechanical gremlins popping up all too often.. I LOVE it when its easy, lol.

[Proto_Man]

depending on how you drive it I wouldn't say ONLY 56K...I know the way I drove mine it probably felt like it had 56K on it when it hit 25K...lol

Well who knows how HE drove it, I just got it. It was 1/2 a quart low on oil when I bought it though, and had 3/32 tread left on the tires. Of course he swapped the ones he had and threw those old crappy things on there, thats pretty obvious. My first "Mods" will be tires and rims, along with denso sp's, K&N filter, and a radar detector, lol.(evil)