thdrill

Little help here: is it possible for the engine on a 2003 Tahoe to hold a code without activating the check engine light. The reason I ask is that last week the light came on and I took it to Autozone who pulled two codes (P0101, and P0455). I know about the P0101 code (as I have been chasing it and thought I found the problem) and the P0455 code I had before and just resecured the gas cap. Within 5 min the light cleared. The reason I ask is that the P0101 code should not have been cleared by the gas cap being resecured. Now the light comes on and clears when I initially start up the truck, however if I've turned the vehicle off and haven't opened the door, the light does not come on at all.

in2pro

I believe that the check engine light will only illuminate as long as the error is present, andmay remain on until the next stop / start cycle.
Some codes will resetthe CE lightafter a certain number of stop start cycles without the error coming back.
The code can be stored for sometime even thou the light no longer comes on, this is a good thing for checking for intermittent issues.

thdrill

So basically as long as the CE light isn't on, I should have no worries. However I should expect the P0101 code to show up on the log as it may be "in memory" on the computer. Thanks

in2pro

Yes,that is my understanding from the exp I have had.

FYI this is what I found on the web for the P0101, if you didnt already have it...
From : http://www.obd-codes.com/
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.



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:
[ul][*]Inspect for the following conditions:
An incorrectly routed harnessInspect 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.[/ul]