Check Engine Light ON and sometimes OFF

[mufutau55]

I had a Check Engine Light on my 2005 EXL Ody, so my Mechanic used ODBII and got those P0XXX error, so we changed all the 6 Ignition Coils and all the 6 Spark Plugs and he cleared the Engine light. But now after about 12 hours the Check Engine Light is back and permanently ON. What next could I check or diagnose as the next step. Thanks.

Mufutau

[dvpatel]

Unless someone has a working crystal ball, P0XXX is not going to cut it. You need to post what the original code(s) were and post the new code(s).

[mufutau55]

Thank you dvpatel. I will obtain the new code from him when I take the van there. I am not sure I remember the old codes nut they were those P codes that tells you which cylinder is not good.
I will come with the new code next time. Thanks.

Mufutau

Unless someone has a working crystal ball, P0XXX is not going to cut it. You need to post what the original code(s) were and post the new code(s).

[dvpatel]

All codes are with P. For example, P0325 is a Knock Sensor code. The cylinder misfire codes are P0301 - P0306. Were the old ones like P030X?

[mufutau55]

Yes. The old codes are the misfire codes of PO30X. I don't know the new codes yet. Thanks.

Mufutau

All codes are with P. For example, P0325 is a Knock Sensor code. The cylinder misfire codes are P0301 - P0306. Were the old ones like P030X?

[New Dad New Van]

It is also not normal to replace all the ignition coils at once. If you have a bad coil then the mech should have done the troubleshooting to find the bad coil.

I hope the OEM NGK spark plugs were installed and not another brand.

[mufutau55]

Well, when we had those codes, we checked the coils and one was damaged (broken) and replaced, then the lights came back ON and we got another code for another cylinder and I changed that coil too, then the light came back reporting another cylinder bad with those PO30X codes, that is when I got mad and decided to changed all of the coils to new HITACHI coils.

Also the spark plugs installed were the OEM NGK ones, I think they are called Iridium or something like that.

But now this morning it took me a long time to get the Van started, so I am now thinking it's something else than the coils and spark plugs.
I will take it to the mechanic again to idagnose and see what we get for new codes.. I will report back.

Mufutau

It is also not normal to replace all the ignition coils at once. If you have a bad coil then the mech should have done the troubleshooting to find the bad coil.

I hope the OEM NGK spark plugs were installed and not another brand.

[mufutau55]

Well.. By the time I get to the Mechanic, the Engine light goes OFF again, so I cannot get an ODBII codes.
I will be back if it comes back ON again.

Mufutau

[dagmando]

The codes are stored until you clear them, even if the light goes off. Go back and he will be able to see what code you had.

[dvpatel]

The codes are stored until you clear them, even if the light goes off. Go back and he will be able to see what code you had.

Negative. Most codes are gone if the light is OFF. That is why the dealers won't even look at the car without the CEL on. Only a handful of codes will stay with the CEL being Off. I know first hand as my Maxima has been running a CEL for EGR low flow for 4 years now.

[mufutau55]

OK. Thanks dvpatel. Yeah! I know the Mechanic told me last time, the liught has to be ON for him to check it.
I will wait until the light comes ON.

But what do you think can cause for the light to be ON and then OFF again vice-versa? Just a guess of course.

Mufutau

[dvpatel]

The light comes on when the OBD system detects a problem. If the problem is resolved, the OBD system turns off the CEL. I used to have that with my EGR. It would come on, then if I drive long (30+ minutes) on the free way, the carbon would be burnt up and then the CEL would go off.

On the same token, if you look around, there are posts on pretty much every forum of people filling up with premium for a tank or two before their emissions test when they have O2 sensor issues.

[mufutau55]

Thank you very much. I will see again when the CEL light comes ON again.
I wonder if adding Fuel Injection Cleaner will help anything, is this recommended.
Thank for you all your help.

Mufutau

The light comes on when the OBD system detects a problem. If the problem is resolved, the OBD system turns off the CEL. I used to have that with my EGR. It would come on, then if I drive long (30+ minutes) on the free way, the carbon would be burnt up and then the CEL would go off.

On the same token, if you look around, there are posts on pretty much every forum of people filling up with premium for a tank or two before their emissions test when they have O2 sensor issues.

[mufutau55]

Feedback:
The CEL Light is still ON, and yesterday I had a hard time starting the van.
When I went to the mechanic today, here is the codes they pulled out with OBDII: P0300, P0301, P0302, P0303, P0304, P0305, P0306 (Random Multiple Cylinder Misfire). This is the same exact codes before we replaced all the 6 spark plugs and all the 6 ignition coils, all parts are OEM.
So guys, what should be my next thing to diagnose? Thank you.

Mufutau

[dvpatel]

I think your mechanic had you replace the coils and plugs for no reason. What other maintenance was done on your van before the misfire codes started. I remember in the past people posted these codes on here after their EGR cleaning. The root cause was a gasket installed backwards. All coils and plugs do not go bad at the same time so your mechanic should have done more diagnostics to determine what's up.

Also, have you had a fill up at an unknown gas station recently? Bad gas would cause misfires too. Water in the gas can cause these as well if I remember correctly.