P0101 -What Does It Mean? (1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 4.8L, 5.3L, 6.0L Chevrolet Silverado And GMC Sierra)

A trouble code P0101: MAF Sensor System Performance Problem tells you that the fuel injection computer is seeing a problem with the MAF sensor signal.

If this code is lighting up the check engine light on your V8 Chevrolet Silverado (GMC Sierra), then this article will help you. I'll explain what this trouble code means and what it takes to solve it.

APPLIES TO: This tutorial applies to the following vehicles:

Chevrolet:

  1. 4.8L Chevrolet Silverado (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
  2. 5.3L Chevrolet Silverado (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
  3. 6.0L Chevrolet Silverado (2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006

GMC:

  1. 4.8L GMC Sierra (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
  2. 5.3L GMC Sierra (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
  3. 6.0L GMC Sierra (2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006

What Does Trouble Code P0101 Mean?

A trouble code P0101: MAF Sensor System Performance Problem tells you that the MAF sensor is reporting an air flow measurement that DOES NOT correlate to the actual throttle plate angle (TPS signal) and engine RPM information the fuel injection computer is receiving from the crankshaft position (CKP) sensor.

When this non-correlating air flow measurement occurs during at least 12 seconds of engine operation, the fuel injection computer sets the P0101 trouble code and lights up the check engine light.

In a nutshell this means that the MAF sensor is reporting a smaller than normal air flow measurement when you're stepping on the gas pedal and engine RPM have increased.

Or the MAF sensor is reporting a larger than normal air flow measurement when the engine is idling (liken when your foot is off the accelerator pedal).

To better understand why this is a problem, take a look at the section: What Does The Mass Air Flow Sensor Do?

Common Symptoms Of A P0101 Trouble Code

The mass air flow sensor's job is to measure the amount of air entering the engine.

The fuel injection computer then uses this air flow measurement (along with other input sensor information) to calculate the amount of fuel to inject into the engine.

Since it's a critical component of the engine management system, when it fails, engine performance will suffer. You'll see one or more of the following symptoms:

  1. Rough or low idle.
  2. Very high idle.
  3. Engine may start and stall.
  4. Little to no acceleration

What Does The Mass Air Flow Sensor Do?

The mass air flow sensor's job is to measure and report the amount of air entering the engine (when it's running) to your Chevrolet Silverado or GMC Sierra's fuel injection computer.

To be a bit more specific: When the throttle plate is at rest (closed), like when the engine is idling, the signal frequency that the MAF sensor produces is low.

Now, as the throttle plate opens and the engine accelerates (which means more air is entering the engine), the mass air flow sensor signal frequency increases.

As the throttle plate closes and the engine returns to idle (due to the decrease in air entering the engine), the mass air flow sensor signal frequency decreases.

As long as the fuel injection computer sees the MAF signal frequency increasing/decreasing in agreement with the info the throttle position and crankshaft position sensors are reporting, it knows more/less air is entering the engine.

What Causes A P0101 Trouble Code?

A bad mass air flow sensor is generally the most common cause of a P0101 trouble code. Before replacing the MAF sensor, it's important to note that several other factors can cause this trouble code.

These other factors that can cause a P0101 trouble code are:

  1. Throttle body inlet screen blocked with debris (if equipped with TB inlet screen).
  2. MAF sensor's hot wires are contaminated.
  3. Intake manifold vacuum leaks (they are notorious for vacuum leaks).
  4. A bad MAP sensor.
  5. An open-circuit or short-circuit problem in the MAF signal wire between the MAF sensor and the fuel injection computer.
  6. An open-circuit or short-circuit problem in the MAF Ground wire.
  7. An open-circuit or short-circuit problem in the MAF power (12 Volt ignition feed) wire.
  8. Bad fuel injection computer (although very rare).

How To Diagnose And Repair A P0101 Trouble Code

Troubleshooting and repairing the trouble code P0101 involves visually inspecting any component involved in piping the air into the throttle body, cleaning the MAF sensor, and finally testing the mass air flow sensor's frequency output.

The first part of your diagnostic tests should be to carefully inspect:

  1. The intake air duct, that connects to the throttle body, for any blockage.
  2. The MAF sensor's inlet screen for blockage.
  3. The mass air flow sensor connector and its wiring for any obvious damage.
  4. The mass air flow sensor's hot wires for contamination.

Cleaning the MAF sensor's wires (if they're dirty) is not hard. This tutorial explains the procedure in detail: How To Clean The GM Mass Air Flow (MAF) Sensor (although the procedure explained here is for the older type of GM MAF sensor, it applies to the newer type of MAF sensor).

After visually inspecting aforementioned components and not finding any problems, the next step is making sure that the mass air flow sensor's frequency signal increases/decreases as you open/close the throttle plate (with the engine running of course).

You can find the MAF signal frequency test explained in detail here: How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L).

Where To Buy The MAF Sensor And Save

AC-Delco is the original equipment replacement part. The following links will help you comparison shop MAF sensor trusted brands (no cheap knockoff parts that only last a few days):

Not sure if the above MAF sensor fits your particular vehicle? No worries, once you get to the site they'll ask you for the particulars of your vehicle and make sure it fits. If it doesn't fit, they'll find you the right one.

More Chevrolet Silverado (GMC Sierra) Tutorials

You can find a complete list of V8 Chevrolet Silverado (GMC Sierra) tutorials in this index:

  1. GM 4.8L, 5.3L, 6.0L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

  1. Resistance Specifications Of The TAC Electronic Throttle Body.
  2. How To Test The GM Accelerator Pedal Position (APP) Sensor 2.
  3. How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L).
  4. Blown Head Gasket Test (GM 4.8L, 5.3L, 6.0L).
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