DTC P0101 Mass Air Flow (MAF) Sensor
Performance
The Mass Air Flow (MAF)
sensor measures the amount of air ingested by the engine. The direct
measurement of the air entering the engine is more accurate than calculating
the airflow from the MAP, the IAT and the engine speed (speed/density). The MAF
sensor has a battery feed, ground, and a signal circuit.
The MAF sensor used on
this engine is a hot wire type. This engine uses the MAF sensor to measure air
flow rate. The MAF output frequency is a function of the power required to keep
the air flow sensing elements (hot wires) at a fixed temperature above the
ambient temperature. Air flowing through the sensor cools the sensing elements.
The amount of cooling is proportional to the amount of air flow. The MAF sensor
requires a greater amount of current in order to maintain the hot wires at a
constant temperature as the air flow increases. The MAF sensor converts the
changes in current draw to a frequency signal read by the PCM. The PCM
calculates the air flow (grams per second) based on this signal.
The PCM monitors the MAF
sensor frequency. The PCM can determine if the sensor is stuck low, stuck high,
not providing the airflow value expected for a given operating condition, or
that the signal appears to be stuck based on a lack of signal variation expected
during the normal operation. This diagnostic tests the range/performance of the
MAF sensor. The MAF system performance or rationality diagnostic uses the MAP,
the IAT, and the engine speed to calculate an expected airflow rate. The PCM
then compares the rate to the actual measured airflow from the MAF sensor. The
PCM only compares the actual MAF value and the calculated value during
conditions where the values are likely to match. This DTC sets if the actual
MAF reading is not within a predetermined range of the calculated reading.
Conditions
for Running the DTC
- DTCs P0102, P0103, P0107, P0108,
P0121, P0122, P0123 not set.
- The engine is running.
- The TP sensor angle is less than 50%
and the engine vacuum (BARO-MAP) is greater than 65 kPa.
- The system voltage is greater than
10 volts but less than 16 volts.
- The change in TP sensor is less than
3%.
- All above conditions stable for 2.0
seconds.
Conditions
for Setting the DTC
- The MAF frequency is 50% different
from the speed density calculation.
- All conditions met for 5.0 seconds.
Action
Taken When the DTC Sets
- The PCM illuminates the malfunction
indicator lamp (MIL) on the second consecutive ignition cycle that the
diagnostic runs and fails.
- The PCM records the operating
conditions at the time the diagnostic fails. The first time the diagnostic
fails, the PCM stores this information in the Failure Records. If the
diagnostic reports a failure on the second consecutive ignition cycle, the
PCM records the operating conditions at the time of the failure. The PCM
writes the conditions to the Freeze Frame and updates the Failure records.
- The PCM utilizes speed density (RPM,
MAP, IAT) for fuel management.
Conditions
for Clearing the MIL/DTC
- The PCM turns OFF the malfunction
indicator lamp (MIL) after 3 consecutive ignition cycles that the
diagnostic runs and does not fail.
- A last test failed, or current DTC,
clears when the diagnostic runs and does not fail.
- A history DTC clears after 40 consecutive
warm-up cycles, if no failures are reported by this or any other emission
related diagnostic.
- Use a scan tool in order to clear
the MIL and the DTC.
Important
- Remove any debris from the PCM connector surfaces
before servicing the PCM. Inspect the PCM connector gaskets when
diagnosing/replacing the PCM. Ensure that the gaskets are installed
correctly. The gaskets prevent water intrusion into the PCM.
- For any test that requires probing the PCM or component
harness connectors, use the Connector Test Adapter Kit J 35616-A .
Using this kit prevents damage to the harness connector terminals. Refer
to Using
Connector Test Adapters in Wiring Systems.
- The following may cause an
intermittent:
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
- Any un-metered air may cause this
DTC to set. Inspect for the following:
- An engine vacuum leak
- The PCV system for vacuum leaks
- An incorrect PCV valve
- The engine oil dip stick not fully
seated
- For an intermittent, refer to Symptoms
.
The numbers below refer
to the step numbers on the diagnostic table.
- The MAF system
performance or rationality diagnostic uses the MAP sensor signal along
with other inputs in order to calculate an expected airflow rate. The PCM
then compares the expected flow rate to the actual measured airflow from
the MAF sensor. The first few steps of this table verify that the MAP
sensor is working properly. Correct any MAP sensor DTCs first. Refer to DTC
P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage if
the MAP sensor voltage is less than 0.8 volts. Refer to DTC
P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage if
the MAP sensor voltage is greater than 4.0 volts.
- Twist the sensor
towards the front of the vehicle and lift upward in order to remove the
MAP sensor.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic
(OBD) System Check? |
-- |
|||
|
If
any MAP sensor DTCs are set, refer to the applicable DTC before proceeding.
Is
the MAP sensor voltage outside of the specified range? |
0.8-4 volts |
Go to DTC
P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage or DTC
P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage |
||
Did
the MAP sensor value change smoothly through the entire range of the test
without any erratic readings? |
-- |
|||
|
Apply
20 inches Hg vacuum to the MAP sensor. Is the MAP sensor reading on the scan
tool the same or less than the specified value? |
34 kPa |
|||
|
Disconnect
the vacuum source from the MAP sensor. Does the MAP sensor reading return to
the original value? |
-- |
|||
Does
the scan tool indicate that this diagnostic failed this ignition? |
-- |
Go to Diagnostic
Aids |
||
Did
you find and correct the condition? |
-- |
|||
Is
the voltage near the specified value? |
5.0V |
|||
|
Connect
the test lamp J
34142-B between the MAF sensor ignition feed and the ground circuit at
the MAF sensor harness connector. Is the test lamp illuminated? |
-- |
|||
|
Is
the voltage less than the specified value? |
4.5V |
|||
Does
the voltage measure near the specified value? |
0.0V |
|||
|
Connect
the test lamp J
34142-B between the MAF sensor ignition feed circuit and the battery
ground. Is the test lamp illuminated? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
|
Locate
and repair the open in the ground circuit to the MAF sensor. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
|
Locate
and repair the open in the ignition feed circuit to the MAF sensor. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
|
Locate
and repair the short to voltage in the MAF sensor signal circuit. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
|
Replace
the MAF sensor. Refer to MAF
Sensor Replacement . Is the action complete? |
-- |
-- |
||
|
Replace
the MAP sensor. Refer to MAP
Sensor Replacement . Is the action complete? |
-- |
-- |
||
|
Important: Program the replacement
PCM. Refer to PCM
Replacement/Programming . Replace
the PCM. Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test ran and passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC table |
System OK |