Circuit Description
The mass air flow (MAF) sensor measures the amount of air which passes through it into the engine during a given time. The PCM uses the mass air flow information to monitor engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle. The MAF sensor produces a frequency signal which can be monitored using a scan tool. 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 be set if the signal frequency from the MAF sensor is lower than the possible range of a normally operating MAF sensor.
Conditions for Setting the DTC
| • | The engine is running. |
| • | TP angle is less than 50%. |
| • | System voltage is greater than 8 volts. |
| • | MAF signal frequency is less than 1200 Hertz. |
| • | The above conditions present for longer than 0.5 seconds + 100 3X reference periods (33 crankshaft revolutions). |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
A low minimum air rate can cause DTC P0102 to be set during deceleration. Check the minimum air rate as follows:
- Run the engine until fully warm (above 85°C / 185°F).
- Disconnect the IAC.
- Install a J 37027-A IAC System Monitor.
- With the engine idling, command the IAC valve to the fully extended position (0 counts).
- With the IAC fully extended, observe the Mass Air Flow reading on the scan tool.
- Check for conditions that can cause a low minimum air rate, including throttle bore and throttle plate coking if the Mass Air Flow reading is less than 2.27 g/sec.
- If the minimum air rate is less than specification, clean or replace the throttle body as necessary. Go to Throttle Body Assembly Replacement .
Check for the following conditions:
| • | Poor connection at the PCM - Inspect harness connectors for the following conditions: |
| - | Backed out terminals. |
| - | Improper mating. |
| - | Broken locks. |
| - | Improperly formed or damaged terminals. |
| - | Poor terminal to wire connection. |
| • | Misrouted harness - Inspect the MAF sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
| • | Damaged harness - Inspect the wiring harness for damage. |
| • | If the harness appears to be OK, observe the scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the fault. |
| • | Plugged intake air duct or filter element - A wide-open throttle acceleration from a stop should cause the Mass Air Flow displayed on a scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or greater at the time of the 1-2 shift. If not, check for a restriction. |
If DTC P0102 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. This may assist in diagnosing the condition.
Test Description
Number(s) below refer to the Step number(s) on the Diagnostic Table:
-
This step verifies that the problem is present at idle.
-
A voltage reading of less than 4 or over 6 volts at the MAF sensor signal circuit indicates a fault in the wiring or a poor connection.
-
Verifies that ignition feed voltage and a good ground are available at the MAF sensor.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||
Is MAF Frequency less than the specified value? | 1.2 kHz (1200 Hz) | |||||||||||||||
3 |
Does the scan tool indicate DTC P0102 failed this ignition? | -- | Refer to Diagnostic Aids | |||||||||||||
4 |
Was a problem found? | -- | ||||||||||||||
Is the voltage near the specified value? | 5V | |||||||||||||||
Connect a J 35616-200 Unpowered Test Light between the MAF sensor ignition feed and ground circuits at the MAF sensor harness connector. Is the test light ON? | -- | |||||||||||||||
7 | Connect the test light between MAF sensor ignition feed circuit and chassis ground. Is the test light ON? | -- | ||||||||||||||
8 |
Was a problem found? | -- | ||||||||||||||
9 |
Was a problem found? | -- | ||||||||||||||
10 | Locate and repair the open in the ground circuit to the MAF sensor. Refer to Wiring Repair in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||||
11 | Locate and repair an open ignition feed fuse or an open in the ignition feed circuit to the MAF sensor. Refer to Wiring Repair in Electrical Diagnosis. Is the action complete? | -- | -- | |||||||||||||
12 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Is the action complete? | -- | -- | |||||||||||||
Replace the PCM. Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||||||||
14 |
Does the scan tool indicate DTC P0102 failed this ignition? | -- | System OK |
