Engine code P0402

[EvancLBZ]

Still no light for me, got a ten hour drive next week so that will tell the tale if its fixed or not.

[eluebke]

I just cleaned the MAF, and I am going to go to the autoparts store to pickup an air filter to replace that next. I will replace it in the parking lot and then clear the code and see what happens. They said they have a WIX paper filter and a K&N filter that fits in the OEM box for $30 more. Does anyone know if the K&N could give me troubles with the code. From what I read some people said that the aftermarket filter made it throw the code also. Or do you think this was just the cold air intake that did this?

[EvancLBZ]

They say that high performance filters such as k&n where you have to oil the filter is hard on maf sensors. The oil will leave a coating on the sensor and it will have to be cleaned. Probably not a huge deal except that the cel will come on telling you there is an issue. From what I have read I would recommend to use the factory ac delco or equivalent filter.

[eluebke]

I ended up buying the WIX filter. I cleared the code and the light stayed out. Now it is just a waiting game to see if a code trips again. I will drive it on the hiway tomorrow to see what happens as this is where it always threw the code in the past.

[eluebke]

No luck for me. I threw a code today driving a steady 55 mph again. Now off to the next step of trying to look at the egr valve and its motor.

[EvancLBZ]

What did you clean the maf sensor with. Compressed air isn't enough usually. I used an electrical cleaner but I've also used a low strength brake and parts cleaner. When I pulled this one out the first time I just blew it off and put it back in, cel light right away. Took it out again and washed it with the cleaner and mine is still ok. Yours still could be the egr plugged up. From what I've read most times it's dirty maf sensors. That info is from identifix which is an online resource for automotive shops.

[eluebke]

I bought a can of mass air flow sensor cleaner made by GUNK. I sprayed it on the small wires and let it dry and then reinstalled the sensor. I guess I could try to spray it down again since it is so easy to do, before I try to go further.

[Pearseam]

I understand trying to do the cheapest thing first but, IMO it really sounds like a EGR blockage and to include the EGR motor is worn out. The EGR cycles at engine start up and operates during crews speeds such as highway driving. I was getting the CEL light on start up. The motor is held on by four screws, it can be replaced without removing the whole EGR. Even though I cleaned the EGR I still had the light coming on until I replaced the motor its been two weeks and no light. In the beginning I also tried different thing to resolve the issue, not until I got off my @$$ and pulled the EGR and cleaned it. The truck runs sooo much better. Do some reading on it before you start, I had to modify a 12 mm off set box end wrench so I could reach the lower bolt of the EGR, tight fit. Putting everything back together went alot faster than the tare down.

[SST 1953]

The oil for the K&N isn't half as bad as carb, brake or parts cleaner is on your MAF sensor. There are a few companies out there that make cleaner especially for the MAF sensor. Screw the EGR, block it and tune it out

[EvancLBZ]

Strongly reccomend the MAF cleaner, or a good quality electrical cleaner. In a pinch a low strength brake cleaner but not if you can get your hands on MAF sensor cleaner. K and N air filter oil is sticky and coats the MAF sensor which only requires you to clean it, nothing bad. Agreed on the high strength brake and parts cleaner being hard on it. For me, i drove 5 hours today on the highway at 120kph and all is good.