P0101 code on 2500 Av when towing (8.1)

[JakeL]

Hey all -

I did a search in the archives and didn't see any super-conclusive answers, so I thought I'd start up a new topic.

Basically, when we do some towing with our Av, the next engine cycle after towing, we'll get a P0101 code set.  Once we are not towing, the MIL goes away, so it seems to be present mostly when there's just a lot of load on the motor for an extended period of time.

The truck runs perfectly at all times - no issues whatsoever.  Just hauls butt and tows amazingly well.  Zero problems.  Just thought I'd stay on top of this issue before it gets any worse.  (It is a  ...)

Only real common fault I saw in the archive was a failed MAP sensor - sound like a good/inexpensive place to start?

Thanks for any additional thoughts.  Approaching 6 months of ownership of the Av, have towed nearly 10,000 miles with it, and couldn't be happier with the truck! 

-Jake

[sperry]

Will this help?

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DTC P0101

Circuit Description 8.1L

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has the following circuits:

   •    An ignition 1 voltage circuit
   •    A ground circuit
   •    A signal circuit

The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. The frequency varies within a range of around 2,000 Hertz at idle to about 10,000 Hertz at maximum engine load. The PCM uses the following sensor inputs in order to calculate a predicted MAF value:

   •    The manifold absolute pressure (MAP)
   •    The intake air temperature (IAT)
   •    The engine speed (RPM)

The PCM compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. DTC P0101 sets if the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value.

Conditions for Running the DTC

   •    DTCs P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0335, P0336, P0401, P0440, P0442, P0443, P0446, P0449, P1111, P1112, P1114, P1115, P1120, P1220, P1221 or P1441 are not set.

   •    The engine is running.
   •    The ignition 1 signal is between 11-18 volts.
   •    The throttle position (TP) indicated angle is less than 95 percent.
   •    The change in the TP indicated angle is less than 5 percent.
   •    The MAP sensor is less than 80 kPa.
   •    The change in the MAP sensor is less than 3 kPa.
   •    The above conditions are met for 1.5 seconds.

Conditions for Setting the DTC

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.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

   •    The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
   •    A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
   •    A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
   •    Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

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.

[JakeL]

Hi Perry -

Thanks for the detailed list. 

All - is any one of the failure modes more common than any other in the 8.1L motor, and a good starting point for fixing the issue? 

Truck is stock except for a K&N and an apparently shop-built Magnaflow exhaust.

Cheers!

-Jake

[sperry]

There is a TSB on the IF Over-oiled K&N use, I'll dig that up..

[sperry]

OK, here it is:

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Info - Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter #04-07-30-013A - (Jan 25, 2005)

2005 and Prior GM Cars and Light Duty Trucks

2005 and Prior Saturn Models

2003-2005 HUMMER H2

This bulletin is being revised to add additional model years and to clarify warranty coverage. Please discard Corporate Bulletin Number 04-07-30-013 (Section 07 -- Transmission/Transaxle).

DO THIS                                                    DON'T DO THIS

First, Inspect the vehicle for a                   DO NOT repair MAF sensors under
reusable aftermarket excessively             warranty if concerns result from the use
over- oiled air filter                                    of an excessively/over-oiled aftermarket,
                                                                  reusable air filter.

The use of an excessively/over-oiled aftermarket, reusable air filter may result in:

   •    Service Engine Soon (SES) Light On
   •    Transmission shift concerns, slipping and damaged clutch(es) or band(s)
   •    Engine driveability concerns, poor acceleration from a stop, limited engine RPM range

The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur.

When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over- oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern.

The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty.

If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs.

Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items.

[JohnBChef]

Sperry,
     I was thinking about this TSB a couple of months ago. We know the MAF sensor hates the K&N oil. When it contacts and dries onto the sensor we know it sends bad data to the PCM. Which triggers the SES light. What do you think about trying to decontaminate the induction system with something like brake cleaner or another solvent. Something that could dissolve and decontaminate the MAF. Then cleaning and blasting it with water or alcohol or air or something.
     When you look at the situation. If the MAF is the problem. It's a $350 part. Trying to decontaminate it VS Repacing a bunch of parts is a helluva lot more affordable. It's an interesting Idea right???
JB

[sperry]

If one is careful, easy-off oven cleaner.. The oil bakes onto it and only cleaning and close inspection would show if it's hurt. Oven cleaner is quite caustic, as we know. The use of it on something like this should be on a genuea pig first, instead. If it pit's the wire surface, it's toast! But one can't scrub it off either, so any other ideas if brake fluid or carb cleaner won't work for some reason?

The wire is heated by a "bias" current from a constant-current source. The resulting voltage varies by the air inrush, the cooling of the wire (I presume they use NiChrome), depends on how much air flows. That varies a control voltage which varies a "clock" pulse generator, for the CPU to reference. It's a fine wire for a quick response obviously. So, one doesn't just scrub it!

[JohnBChef]

See not such a crazy Idea.  Once again I strongly advise that IF you were to try it. You must be willing to accept the consequences of losing the part if it's damaged and the inherent serious cost to replace it. MAF sensors are not cheap! But when you have to choose between maybe replacing VS Certainly replacing. This suggestion gives you an option. Good Luck
JB

[sperry]

I'll keep my stock Hi-Cap air cleaner...

[JakeL]

Thanks for all the ideas fellas - I'll definitely give some things a try... 

-Jake

[sperry]

Good Luck!