2G CEL Light - No Codes Thrown + Bad MPG

[GofaST4life]

Whats up guys...

I did do some searching, but there seems to be a lot of threads with CEL issues so it was hard to find.

Anyway, My DSM's CEL has been coming on and every time I take it to have the codes scanned, no codes are shown.

I'm not sure what else to do. After the light pops on, Ill reset everything to turn it off, but after maybe 10-15 min of driving it just pops back on.



Also, I've noticed my MPG is really not that great, I think i'm getting around 13-15mpg's. I by no means drive this car hard, and make it a point to drive efficiently. I'm thinking of changing the plugs/wires and checking for boost leaks. Not sure what else I should look for.

 

[skatershawn]

That's a good start! I would say bad MPG could be caused by a faulty o2 sensor also.

 

[L1v1ng L3g3nd]

Bad Front O2 Sensor for sure.
Had the same problem. Check engine light turned on after the car got the normal driving temperature. CEL was always O2 sensor heater malfunction...

 

[GofaST4life]

I will surely have the O2 sensor checked.

But, wouldn't that throw a code?

Im curious as to why my CEL is on, yet no codes are able to be scanned or scene.

 

[L1v1ng L3g3nd]

Yeah, your code should be "O2 sensor heater malfunction"

Maybe there is something wrong with your OBD interface

Do you check the codes with ECMLink?

 

[GofaST4life]

I was also thinking there may be an ODB interface issue.

I have been checking them with your generic code scanner. I don't have ECMlink available.

 

[Kevin4G63]

At my work we often have the same problem. Lights keeps popping on and no codes shown.
Always turns out the be the heater-core from the o2 sensor. You can easily measure the resistance(just take the sensor-plug), if there isn't any it's broke.

From what I know is, when the engine is hot it doesn't use the heater-core. When you start your car 3-4 times whens it hot, obd erases the code right?

 

[GofaST4life]

I'm going to change out the plugs, wires and front O2 today after work.

Then ill reset the CEL and see what happens.

 

[Miakehl]

I'm going to change out the plugs, wires and front O2 today after work.

Then ill reset the CEL and see what happens.

Good start, a bad o2 can also cause the computer to throw a lean code or a fuel trim code. They all pretty much point to the o2 as these have a tendency to go out. If you haven't replaced/had it replaced it's a good idea to do it anyway.

If you do that and it's still throwing codes it could point to the MDP sensor (the sensor on top of the intake manifold.)

YMMV but on my car I was throwing lean codes, then fuel trim codes so I replaced the front o2 and it was happy for like a week. Then the ecu decided randomly that the MDP was bad, I replaced it and it all went away.

For the record, the front o2 isn't just a r&r, it's actually kind of a pain on a GS-t with the heatshield and the stupid long wire and all.

 

[GofaST4life]

Miakehl - Thank you for the heads up.

Ill be picking up an O2 and wires from Autozone today or tomorrow and get them installed.



I called my local shop, and they wanted $425.00 to do plugs, wires, O2 sensor, with labor...heck, its going to cost me under $125 for the parts only...geeze.

 

[skatershawn]

Plugs, wires, and o2 sensor are all extremely easy to accomplish, save the money from having a shop do it, and do it yourself.
Total time should take ~30min.
It's just the o2 senor can be a pain sometimes, and requires a o2 sensor socket (if you want to use a socket and ratchet)

 

[Groundation]

You can rent the special O2 socket tool for free from some parts stores, just have to put down a deposit.

 

[GofaST4life]

Awesome guys, thank you!

That will surely make things much easier.

 

[gusu]

To test a O2 sensor manually is easy.

Take a propane torch, take the negative end of the wire and touch it to the metal end of the O2 sensor. I usually use a ziptie to hold it in place, then take your positive end and ouch it to the connector side.

If it is good it should be able to read .9 volts in less than a minute and should fully cool down to at least .008 volts in less than 3 seconds. If not, it's a piece of shit.

 

[GofaST4life]

So Autozone was going to get me the parts for $125ish.

Just checked out RockAuto.com and I can get everything for $45. Bosch Plug Wire set and Ultra Power OE O2 sensor!

RockAuto FTW!