scrnchr

2004 Tahoe LS 4WD

I'm still getting the P0101 MAF DTC. I cleaned the MAF wires with carb cleaner and reset the code but it comes back. Some info is below, but I'm not sure what to do next. Nothing has changed with the cable routing. Is it worthwhile to change the air filter? It looks pretty new. I've read about "MAF cleaner" but other threads/videos say to clean the wires with carb/brake cleaner. Any ideas? Thanks.



P0101 OBD-II Trouble Code

Technical Description

Mass Air Flow (MAF) Circuit Range/Performance Problem

What does that mean?

Basically this means that there is a problem with the Mass Air Flow (MAF) sensor or circuit. The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 4.0 seconds. Other MAF sensor circuit DTC trouble codes are P0100, P0102, P0103, and P0104.

Symptoms

You will likely not notice any serious drivability problems, although there may be symptoms.

Possible Solutions

The simplest thing to do is to reset the code and see if it comes back. Then start with the cheapest, easiest repair procedures:

Inspect for the following conditions:

An incorrectly routed harness--Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components:
- The secondary ignition wires or coils
- Any solenoids
- Any relays
- Any motors

A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.

A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 6-12 g/s at idle to 230 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.

The barometric pressure (BARO) that is used in order to calculate the predicted MAF value is initially based on the MAP sensor at key ON.

When the engine is running the MAP sensor value is continually updated near WOT. A skewed MAP sensor will cause the calculated MAF value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.

A high resistance on the ground circuit of the MAP sensor can cause this DTC to set.

Any loss of vacuum to the MAP sensor can cause this DTC to set.

If you suspect the condition may be related to aftermarket accessories, refer to Checking Aftermarket Accessories in Wiring Systems.

kevinkpk

Have you changed anything in the air intake?

MDTAHOE

More than likely you have an intake vac leak. Does the truck run bad or idle low on cold start? Very common problem and will set a MAF code.

scrnchr

No -- I mean, I did remove the MAF sensor to clean it, but it was already throwing the code then, and I put it all back together.

scrnchr

Actually, yes, I have noticed that the truck doesn't idle as well. One thing about this Tahoe is that I was always amazed at how quiet and smooth the idle was--sitting inside, you almost couldn't tell the engine was running. Now when I start it cold, it shudders a bit and hunts a little on rpm, and you can definitely tell it's running. I was thinking this was being caused by the MAF sensor messing up, but you're saying it could be a symptom of a different problem that is also causing the MAF code.

How do I check for an intake vacuum leak? I don't even know where to start.......

MDTAHOE

Replace the intake gasket it is your problem. You described the exact symptom. I guess it runs ok after it is warm?

scrnchr

I looked up some threads on replacing the intake manifold gasket. It doesn't look horrible, but it's not trivial either. Are there any simple things I could try first, or is there some way to confirm it's the gasket? Even some way to limp past emissions so I could wait until spring to replace the gasket. I'm in Wisconsin, and it snowed here today. >

MDTAHOE

No temporary fix the problem, it is only going to get worse. Eventually it may not run at all.

MDTAHOE

You could get it smoke checked for a vac leak.

scrnchr

Just to try a few things, I opened up the air filter box and vacuumed it out good, although there was very little dirt on the bottom anyway. I also vacuumed out the filter, which looks pretty new.

I checked the oil dipstick and underside of oil fill cap for any signs of coolant and didn't find any. There's nothing dripping under the truck, and no puddles on top of the engine block that I could see.

I took the VORTEC cover off the top of the engine and took a look at the vac lines. I also jiggled and pushed down what I think is the EVAP purge solenoid near the front top of the intake manifold.

I started the truck and for some reason the CEL is now off. I checked the codes and the P0101 is still there, and the EVAP is still NOT READY (about 2 or 3 days since I reset codes). The truck was idling great, started cold.

I carefully sprayed carb cleaner all around the base of the intake manifold, except in back where I couldn't get at it. The rpm never changed a bit.

Put the VORTEC cover back on, then cycled the ignition from OFF to ON (not start) five times--I thought I read somewhere that this might clear a P0101, but I'm sure I'm mistaken. Anyway, it didn't--the P0101 is still there (and did a rescan with the reader), and the EVAP still isn't set.

So I'm going to give it a few days to let the EVAP set (I replaced the vent solenoid due to EVAP DTC codes and am waiting to see if it helped). And to see if the P0101 might go away.

Any thoughts?

Thanks.