DTC P0101

Circuit Description

The mass air flow sensor (MAF) is an air flow meter that measures the amount of air that enters 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 that enters the engine indicates deceleration or idle. A large quantity of air that enters the engine indicates an acceleration or a high load situation. The MAF sensor has an ignition 1 voltage circuit, a ground circuit, and 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 that is based on inlet air flow through the sensor bore. The PCM uses the barometric pressure (BARO), the throttle position (TP), intake air temperature (IAT), and the engine RPM in order to calculate a predicted MAF value. The PCM compares the actual MAF sensor signal to the predicted MAF value. This comparison will determine the following conditions: The signal is stuck based on a lack of variation. The signal is too low or too high for a given operating condition. DTC P0101 will set if the actual MAF sensor signal is not within a predetermined range of the calculated value.

Conditions for Running the DTC

DTCs P0102, P0103, P0107, P0108, P0401, P0404, P0405, P0440, P0442, P0446, P0606, P01404, P01441, P1514, P1515, P1516, or P1517 are not set.
DTCs P1120 and P1220 as a combination are not set.
DTC P1518 is not set in combination with any of the following DTCs: P1120, P1125, P1220, P1221, P1271, P1272, P1273, P1275, P1276, P1280, P1281, P1285, P1286.
The engine is running.
The ignition 1 signal is at least 9 volts and not more than 18 volts.
The throttle position (TP) indicated angle is less than 30 percent.
The TP indicated angle is steady within a range of 5 percent.
The manifold absolute pressure (MAP) sensor is greater than 20 kPa.
The MAP sensor is steady within a range of 5.2 kPa.

Conditions for Setting the DTC

The actual MAF sensor signal is not within a predetermined range of the calculated value.
The above condition is present for greater than 40 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:

A misrouted harness--Inspect the harness of the MAF sensor in order to verify that the harness is not routed too close to the following components:
- Secondary ignition wires or coils
- Solenoids
- Relays
- Motors
Deposits on the throttle plate or in the throttle bore
Unmetered air--Any unmetered air that enters the engine may cause this DTC to set. Verify that the oil dipstick is completely seated and the oil filler cap is secure.
The MAF display should increase from 4-7 g/s at idle to 130 g/s or more at the 1-2 shift during a wide-open throttle (WOT) acceleration. If not, inspect for a restriction.
The barometric pressure that is used in order to calculate the predicted mass air flow value is based on the MAP sensor reading at key ON. A skewed MAP sensor will cause the calculated mass air flow 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 displayed at or near sea level. The value decreases by approximately 3 kPa for every 305 M (1,000 feet) of altitude.
Inspect for an unresponsive MAP sensor due to the following conditions:
- Poor vacuum connections
- A damaged vacuum source
- Any defective vacuum hoses
- Any unmetered air into the manifold

If you suspect the vehicle condition may be related to aftermarket accessories, refer to Checking Aftermarket Accessories in Wiring Systems.

If the condition is intermittent, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

Any unmetered air that enters the engine may cause this DTC to set. This step eliminates any conditions which can cause a DTC to set with a MAF sensor that is operating correctly.
This step verifies the signal circuit from the MAF sensor electrical connector to the PCM. A voltage reading of less than 4 volts, or more than 6 volts, indicates a poor connection or a malfunction in the wiring.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics
1	Did you perform the Diagnostic System Check-Engine Controls?	--	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Install a scan tool. Start the engine. Monitor the Diagnostic Trouble Code (DTC) Information using the scan tool. Does the scan tool display any other DTCs set?	--	Go to Diagnostic Trouble Code (DTC) List	Go to Step 3
3	Observe and record the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or within the parameters observed in the Freeze Frame/Failure Records. Does the DTC fail this ignition?	--	Go to Step 4	Go to Diagnostic Aids
4	Let the engine idle at the normal operating temperature. With a scan tool, observe the MAP sensor voltage parameter. Does the scan tool indicate that the voltage is within the specified range?	0.8-4.0 V	Go to Step 5	Go to Manifold Absolute Pressure (MAP) Sensor Diagnosis
5	Turn OFF the ignition. Inspect for the following conditions: Objects that are blocking the air inlet screen of the MAF sensor. A dirty air filter element or an intake air duct that is obstructed or collapsed. Inspect for vacuum leaks in the following components: The intake manifold The throttle body The EGR valve flange and the pipe The MAF sensor seal The MAP sensor seal The seal on the evaporative emission (EVAP) canister purge valve The crankcase ventilation system The brake booster system The air induction system Did you find and correct the condition?	--	Go to Step 22	Go to Step 6
6	Remove the MAP sensor from the engine vacuum source. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement . Leave the electrical harness connected. Connect a hand operated vacuum pump to the MAP sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe or record the kPa parameter display of the MAP sensor. At the same time, SLOWLY apply vacuum 1 inch Hg at a time up to 20 inches Hg which is indicated on the pump gage. Each 1 inch of vacuum applied should result in a 3 kPa to 4 kPa drop in the MAP sensor value on the scan tool. The value should change smoothly with each 1 inch increase in vacuum. Does the scan tool indicate that the MAP sensor value changed smoothly through the entire range of the test?	--	Go to Step 7	Go to Manifold Absolute Pressure (MAP) Sensor Diagnosis
7	Apply 20 inches Hg vacuum to the MAP sensor. Does the scan tool indicate that the MAP sensor value is equal to or less than the specified value?	34 kPa	Go to Step 8	Go to Manifold Absolute Pressure (MAP) Sensor Diagnosis
8	Disconnect the vacuum source from the MAP sensor. Does the scan tool indicate that the MAP sensor value returned to the original value that was observed in Step 6?	--	Go to Step 9	Go to Manifold Absolute Pressure (MAP) Sensor Diagnosis
9	Turn OFF the ignition. Disconnect the harness connector of the MAF sensor . Refer to Mass Air Flow (MAF) Sensor Replacement . Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Refer to Circuit Testing in Wiring Systems. Does the voltage measure near the specified value?	5.0 V	Go to Step 10	Go to Step 11
10	Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and the ground circuit of the MAF sensor. Refer to Circuit Testing in Wiring Systems. Does the test lamp illuminate?	--	Go to Step 18	Go to Step 13
11	Is the voltage less than the specified value?	4.5 V	Go to Step 14	Go to Step 12
12	Turn OFF the ignition. important Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit. Disconnect the PCM. Refer to Powertrain Control Module (PCM) Replacement . Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Refer to Circuit Testing in Wiring Systems. Does the voltage measure near the specified value?	0.0 V	Go to Step 19	Go to Step 17
13	Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and of a good ground. Refer to Circuit Testing in Wiring Systems. Does the test lamp illuminate?	--	Go to Step 15	Go to Step 16
14	Turn OFF the ignition. Disconnect the PCM. Refer to Powertrain Control Module (PCM) Replacement . Test the signal circuit between the MAF sensor and the PCM for the following conditions: A high resistance or an open A short to ground A short to the ground circuit of the MAF sensor--Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 22	Go to Step 19
15	Repair the high resistance or an open in the ground circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	--	Go to Step 22	--
16	important The ignition 1 voltage circuit of the MAF sensor is spliced to other components on the vehicle. Refer to Power Distribution Schematics in Wiring Systems. Repair the short to ground or an open in the ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Replace the fuse if necessary. Did you complete the repair?	--	Go to Step 22	Go to Step 20
17	Repair the short to voltage in the signal circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	--	Go to Step 22	--
18	Inspect for poor connections at the harness connector of the MAF sensor. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 22	Go to Step 20
19	Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 22	Go to Step 21
20	Replace the MAF sensor. Refer to Mass Air Flow (MAF) Sensor Replacement . Did you complete the replacement?	--	Go to Step 22	--
21	Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement?	--	Go to Step 22	--
22	Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. Does the DTC run and pass?	--	Go to Step 23	Go to Step 2
23	With a scan tool, observe the stored information in Capture Info. Does the scan tool display any DTCs that you have not diagnosed?	--	Go to Diagnostic Trouble Code (DTC) List	System OK