Circuit Description
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 deceleration or idle. A large quantity of air entering the engine indicates an acceleration or 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 based on inlet air flow through the sensor bore. The frequency will vary within a range of around 2,000 Hertz at idle to about 10,000 Hertz at maximum engine load. DTC P0102 will set if the PCM detects a frequency signal lower than the possible range of a normally operating MAF sensor.
Conditions for Running the DTC
| • | The engine is cranking for 0.5 second or running for 1 second. |
| • | The engine speed is at least 50 RPM. |
| • | The Ignition 1 signal is greater than 8 volts. |
| • | The idle air control (IAC) position is greater than 5 counts. |
| • | All of the above conditions are present for greater than 1 second. |
Conditions for Setting the DTC
| • | The MAF sensor frequency signal is less than 1,200 Hz. |
| • | The above condition is present for more than 12 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 MAF sensor harness in order to ensure that the harness is not routed too close to the following components: |
| - | The secondary ignition wires or coils |
| - | The solenoids |
| - | The relays |
| - | The motors |
| • | A low minimum air rate may cause this DTC to set during deceleration. Inspect for the following conditions: |
| - | A plugged or collapsed intake air duct or dirty air filter element |
| - | Objects blocking the MAF sensor air inlet screen |
| - | Throttle bore and throttle plate coking |
| • | A wide open throttle (WOT) acceleration from a stop should cause the Mass Air Flow display on a scan tool to increase from about 4-7 gm/s at idle to about 130 gm/s or more at the time of the 1-2 shift. If not, inspect for a restriction. |
| • | Any unmetered air entering the engine may cause this DTC to set. Inspect for vacuum leaks anywhere downstream of the MAF sensor. |
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.
-
This step verifies the signal circuit from the MAF sensor electrical connector to the PCM. A voltage reading of less than 4 volts or greater than 6 volts indicates a malfunction in the wiring or a poor connection.
-
This step tests the signal circuit of the MAF sensor for a short to another 5 volt reference circuit.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Does the scan tool indicate that the MAF sensor frequency is less than the specified value? | 1200 Hz | Go to Step 4 | Go to Step 3 | ||||||
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||||
4 | Inspect the fuse that supplies the ignition 1 voltage circuit of the MAF sensor. Is the fuse open? | -- | Go to Step 14 | Go to Step 5 | ||||||
Does the voltage measure near the specified value? | 5 V | Go to Step 6 | Go to Step 8 | |||||||
Do any additional DTCs set? | -- | Go to Step 16 | Go to Step 7 | |||||||
7 |
Does the test lamp illuminate? | -- | Go to Step 18 | Go to Step 11 | ||||||
8 | Does the voltage measure less than the specified value? | 4.5 V | Go to Step 10 | Go to Step 9 | ||||||
9 |
important: Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit. Refer to Circuit Testing in Wiring Systems.
Does the voltage measure near the specified value? | 0 V | Go to Step 12 | Go to Step 15 | ||||||
10 |
Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 12 | ||||||
11 | Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Circuit Testing in Wiring Systems. Does the test lamp illuminate? | -- | Go to Step 13 | Go to Step 14 | ||||||
12 | Test for continuity at the harness connector of the PCM from the signal circuit of the MAF sensor to all other circuits at both PCM connectors. Refer to Circuit Testing in Wiring Systems. Does the DMM indicate continuity between any other circuit? | -- | Go to Step 17 | Go to Step 19 | ||||||
13 | 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 | -- | ||||||
14 |
Important: The ignition 1 voltage circuit of the MAF sensor is spliced to other components of the vehicle. Did you complete the repair? | -- | Go to Step 22 | Go to Step 20 | ||||||
15 | 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 | -- | ||||||
16 | Repair the short between the signal circuit of the MAF sensor and the circuit for which the DTC set. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 22 | -- | ||||||
17 | Repair the circuits that are shorted together. 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 Conditions and Poor Connections and 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 Conditions and Poor Connections and 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 Airflow Sensor Replacement . Did you complete the replacement? | -- | Go to Step 22 | -- | ||||||
21 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 22 | -- | ||||||
22 |
Does the DTC run and pass? | -- | Go to Step 23 | Go to Step 2 | ||||||
23 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||
