P0068 Code W/ K&N CAI

[ptparker]

I put on the K&N CAI about 500 miles/2 weeks ago, but now I have a problem. I will be driving down the road, and the car will go into limp mode. When I read the code, it comes back "P0068 MAF/MAP Sensor Throttle Position Correlation", but if I look at the DTC list here it comes back "P0068 Throttle Body Airflow Performance ECM". I am wondering if the description from the handheld code reader is just a more generic description, not specific to our engines/PCM's.

So here is what I have done, I have taken out my MAF sensor and cleaned it out with throttle cleaner. There was a light coating of oil on it, I assume from the K&N Cone. It seemed to have fixed the problem for a couple days, but now it is back. Also it has nothing to do with how hard I am driving the car. Most of the time it happenes in the 40-60 mph while I am cruising.

What are your guys thoughts about this? I am thinking about taking off the intake pipes and giving them a good spraying. Am I barking up the wrong tree?

[clownhair]

Originally Posted by ptparker

I put on the K&N CAI about 500 miles/2 weeks ago, but now I have a problem. I will be driving down the road, and the car will go into limp mode. When I read the code, it comes back "P0068 MAF/MAP Sensor Throttle Position Correlation", but if I look at the DTC list here it comes back "P0068 Throttle Body Airflow Performance ECM". I am wondering if the description from the handheld code reader is just a more generic description, not specific to our engines/PCM's.

So here is what I have done, I have taken out my MAF sensor and cleaned it out with throttle cleaner. There was a light coating of oil on it, I assume from the K&N Cone. It seemed to have fixed the problem for a couple days, but now it is back. Also it has nothing to do with how hard I am driving the car. Most of the time it happenes in the 40-60 mph while I am cruising.

What are your guys thoughts about this? I am thinking about taking off the intake pipes and giving them a good spraying. Am I barking up the wrong tree?

yep the handheld scanners are just the general code. The redline DTC is the one to go off.

[WopOnTour]

Originally Posted by ptparker

I put on the K&N CAI about 500 miles/2 weeks ago, but now I have a problem. I will be driving down the road, and the car will go into limp mode. When I read the code, it comes back "P0068 MAF/MAP Sensor Throttle Position Correlation", but if I look at the DTC list here it comes back "P0068 Throttle Body Airflow Performance ECM". I am wondering if the description from the handheld code reader is just a more generic description, not specific to our engines/PCM's.

So here is what I have done, I have taken out my MAF sensor and cleaned it out with throttle cleaner. There was a light coating of oil on it, I assume from the K&N Cone. It seemed to have fixed the problem for a couple days, but now it is back. Also it has nothing to do with how hard I am driving the car. Most of the time it happenes in the 40-60 mph while I am cruising.

What are your guys thoughts about this? I am thinking about taking off the intake pipes and giving them a good spraying. Am I barking up the wrong tree?

Actually these DTC descriptions are just different ways of stating the same thing.This DTC is unfortunately very common when using a CAI (especially one that is ACTUALLY WORKING!) Here are the basic enable criteria for a P0068 from the FSM

The powertrain control module (PCM) uses the following information to calculate an expected airflow rate:

• The throttle position (TP)

• The barometric pressure (BARO)

• The super charger inlet pressure (SCIP)

• The intake air temperature (IAT)

• The mass air flow (MAF)

• The engine RPM

If the PCM detects the airflow rate is more than expected, DTC P0068 sets.

Basically the MAF is saying it's seeing more airflow than what the ECM is expecting based on conditions and values from other sensors. Unfortunately I dont know what you are going to be able to do about this, other than using your code reader to clear just the DTC when it sets. In a perfect world you would go into the ECM table where the outside "tolerance %" for this DTC was stored and make it larger- fixed. Too bad nobody has hacked this box...YET!

It stiill could be a bad MAF (since few others have commented on this DTC) but you might have trouble getting your dealer to look at it unless you swapped all of you facory intake back in first. Maybe you have a buddy you can swap MAFs with to diagnose??

ALSO- dont use carb cleaner on a MAF as it can damage it if it is the corrosive solvent type (like GM Cleens) Use only the type with high alcohol content that evaporates immediately when you spray it on your hand.(freezing it off in the process - lol)
I actually use GM BrakeCleen for MAF cleaning, never had a problem
WOT

[Sp00ner]

Ahhh... so there we go.. any idea what that parameter looks like Wop? You would think that it's pretty small if just a CAI is setting it off...

[DanM]

Hey Wop, Not to second guess at all. But from your post, you seem to suggest that it's a lookup table ("expected value") check. Are you sure that's the case? The code description "P0068 MAF/MAP Sensor Throttle Position Correlation" seems to suggest that it's more of a MAF/MAP/Throttle rationality check, in which case you would think that the ECM would be able to cope with it just fine w/o failing (as long as none of the sensors were out of range). I'm just wondering if maybe he has a leak/obstruction somewhere, or if the airflow through the MAF is unusual or something. Not ready to give up just yet, cause lots of ppl use intakes w/o problems!

[Sp00ner]

Mine has been off for 3 weeks, I think, at this point. The temps have been from 93-58 in the last two weeks too. I'm not sure that it's solved, but it sure seems to have gone away. Perhaps the ECU needs time to adjust??? How long does an ECU take to adjust to something like that? Is it nearly instant, or does it slowly rebuild the tables to match?

[DanM]

Well that's the thing - the ECM doesn't "adjust" to airflow numbers as far as I understand (not as in updating its tables). It will have some sort of rationality check that compares MAP to MAF to temp to TPS to whatever to make sure that all the values "agree" with one another. Ie if you read huge MAF and TPS=WOT, but MAP says high vacuum, something is wrong, and you fail the rationality check.

The thing is, because it's a rationality check, as long as everything is working properly, it SHOULD be able to cope with more airflow (as long as the other parameters, like MAP, agree with it). That's the reason I wonder if maybe he's got a vac leak or something somewhere. Otherwise, if it can't cope with relatively minor changes in air flow, you'd set codes left & right when you got a dirty air filter, and obviously that's not the case....

[ptparker]

Ok, so this is good info, guys...
DanM, the "P0068 MAF/MAP Sensor Throttle Position Correlation" description is the more generic one coming off the code reader. The Airflow description is the specific one for our cars.

I do not know anyone if the area (Raleigh, Durham, Chapel Hill, Cary, etc) with an RL. So, if anyone in the area wants to participate in a small experment, PM me.

BTW, when I cleaned the sensor, I used fuel injector/throttle cleaner, not carb cleaner. It is just like brake cleaner, but i think it might even be lighter/faster evap rate.

Also what is the part number/how much is a new MAF to try it out?

[DanM]

Originally Posted by ptparker

Ok, so this is good info, guys...
DanM, the "P0068 MAF/MAP Sensor Throttle Position Correlation" description is the more generic one coming off the code reader. The Airflow description is the specific one for our cars.

I do not know anyone if the area (Raleigh, Durham, Chapel Hill, Cary, etc) with an RL. So, if anyone in the area wants to participate in a small experment, PM me.

BTW, when I cleaned the sensor, I used fuel injector/throttle cleaner, not carb cleaner. It is just like brake cleaner, but i think it might even be lighter/faster evap rate.

Also what is the part number/how much is a new MAF to try it out?

Yah I hear you... the descriptions both mean the same thing. Are you 100% sure you don't have a vac leak somewhere, and that everything is installed correctly?? Not sayin I don't believe you, but a little leak between the intake and TB will cause a code like this real easy.... have you done the soapy water thing to look for leaks?

[ptparker]

Originally Posted by DanM

Yah I hear you... the descriptions both mean the same thing. Are you 100% sure you don't have a vac leak somewhere, and that everything is installed correctly?? Not sayin I don't believe you, but a little leak between the intake and TB will cause a code like this real easy....

That is a really good thought... I will check it out... I looked at the joint where the two tubes meet, but I did not very carfully check the connection to the TB and the connection at the cone. It just sucks to have to take off the wheel/wheel well to get to that damn cone.

That would make sence, the connection at the TB being loose, b/c then air would be entering the system past the sensor... I will check it out tonight.