P0101

DTC P0101

CIRCUIT DESCRIPTION
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air that enters the engine. It is fitted between the air cleaner and turbocharger. A small quantity of air that enters the engine indicates deceleration or idle. A large quantity of air that enters the engine indicates acceleration or a high load condition. The MAF sensor has the following circuits.
- Ignition voltage circuit
- Low reference circuit
- MAF sensor signal circuit

The engine control module (ECM) monitors the MAF sensor signal voltage. This output voltage will display on the scan tool as a voltage parameter and as a grams per second (g/s) parameter. The ECM will calculate a predicted MAF value. The ECM compares the actual MAF sensor voltage signal to the predicted MAF value. This comparison will determine if the signal is stuck, or is too low or too high for a given operating condition. If the ECM detects that the actual MAF sensor signal voltage is not within a predetermined range of the calculated MAF value, this DTC will set.

Condition for Running the DTC
- DTCs P0016, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0201, P0202, P0203, P0204, P0261, P0264, P0267, P0270, P0300, P0301, P0302, P0303, P0304, P0335, P0336, P0401, P0403, P0404, P0405, P0406, P0477, P0478, P0500, P0506, P0507, P0602, P0642, P0643, P1125, P1293, P2146, P2147, P2148 P2149, P2150, P2151, P2227, P2228 and P2229 are not set.

AND following conditions are met longer than 3 seconds.
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.
- The engine is running.
- The barometric pressure (BARO) is between 10.9 -17.4psi (75- 120 kPa).
- The intake air temperature (IAT) is between 19 -248 °F (-7- 120° C).
- The engine coolant temperature (ECT) is between 149-198 °F (65-92° C).
- The engine speed is lower than 3600 RPM.
- The engine speed does not vary more than 50 RPM.
- The fuel injection quantity does not vary more than 10 cu.mm.
- The EGR control is commanded OFF.
- The exhaust brake control is commanded OFF.

Condition for Setting the DTC
- The ECM detects that the MAF sensor signal voltage is not within a predetermined range of the calculated MAF value for longer than 8 seconds.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive driving cycle when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records on the second consecutive driving cycle when the diagnostic runs and fails.

Condition for Clearing the MIL/DTC
- The ECM turns OFF the MIL after 3 consecutive driving cycles when 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 after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
- Any unmetered air that enters the engine downstream of the MAF sensor may cause this DTC to set.
- High resistance in the MAF sensor circuit may set this DTC.
- A short between the signal circuit of the MAF sensor and the signal circuit of the intake air temperature (IAT) sensor will skew the MAF sensor lower than normal at higher air flows.
- Normal MAF reading on the scan tool with the engine running in Park or Neutral at idle are around 25 g/s to 220 g/s or more in Park or Neutral at W.O.T. (accelerator pedal full travel).

If an intermittent condition is suspected, the following may cause an intermittent:
- The MAF sensor harness routed too closely to fuel injection wiring or components.
- The MAF sensor harness routed too closely to after-market add-on electrical equipment.
- Poor connections
- Misrouted harness
- Rubbed through wire insulation
- Broken wire inside the insulation

Check for the following conditions:
- Poor connection at the ECM: Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness for damage. If the harness appears to be OK, observe the "MAF Sensor" display on the scan tool with engine running while moving connectors and wiring harness. A change in the display will indicate the location of the fault.

Test Description
The number below refers to the step number on the diagnostic table.
3. A skewed barometric pressure (BARO) sensor value can set this DTC. The BARO on the scan tool should read near boost pressure with the key ON and engine OFF.

DTC P0101
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views

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