Schematic Reference: Engine Controls Schematics
Circuit Description
The mass air flow (MAF) sensor measures the amount of air which passes through it in a given amount of time. The Engine Control Module (ECM) uses this information to determine the operating requirements of the engine in order to control fuel delivery. The ECM calculates the engine's fuel requirements by monitoring the current flow on the signal wire from the MAF sensor. When the volume of air entering the MAF sensor increases, the current flow seen by the ECM from the MAF sensor also increases. When the air flow decreases, the current seen by the ECM also decreases. The MAF sensor is located between the air intake tube and the air cleaner in the LH front area of the engine compartment.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | MAF sensor output current is greater than 4.9 mA. |
| • | Condition is present for longer than 5 seconds. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
| • | The ECM will enter the Fail-Safe Function and determine injector drive time according to TP sensor and engine speed. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn off after three consecutively passing cycles without a fault present. |
| • | A History DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using a scan tool or by disconnecting the ECM battery feed. |
Diagnostic Aids
Check for any of the following conditions:
| • | MAF sensor readings vary with the air temperature and barometric pressure. The specifications indicated are at 20°C (68°F) and sea level. |
| • | A misrouted wiring harness. Inspect the MAF sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
| • | A damaged wiring 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. |
| • | Check for a restriction. A plugged intake air duct or a dirty air filter element. A wide open throttle (WOT) acceleration from a stop should cause the MAF displayed on the scan tool to increase from about 2 to 3.5 grams per second at idle to 100 grams per second or greater at the time of the 1-2 shift. |
An intermittent malfunction may be caused by a fault in the MAF sensor circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector locks. |
| • | Improperly formed or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
If the DTC P0103 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step will determine if the fault is present.
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Review Freeze Frame data to determine when the DTC set. Always record this information.
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Normal voltage at idle for the MAF sensor signal circuit should be 1.7 volts to 2.0 volts. This voltage reading should increase steadily to 5 volts when engine speed is increased to approximately 4000 RPM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the MAF sensor display above the specified value? | 21.2 g/sec | |||
Is DTC P0103 set? | -- | Fault Not Present-Go to Diagnostic Aids | ||
4 |
Is the voltage within the specified value? | 1.0 to 1.6 volts | ||
|
Important: MAF sensor readings vary with the air temperature and barometric pressure. The specifications indicated are at 20°C (68°F) and sea level.
Does the voltage rise approximately to the specified value when the engine speed is increased? | From 1.6 volts at idle up to 3.0 volts at 4000 RPM | |||
6 |
Is the test light ON? | -- | ||
7 | Check for a faulty connection at the MAF sensor and at the ECM. Repair as necessary. Was a repair necessary? | -- | ||
8 | Locate and repair the open circuit in the ground circuit to the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
9 | Check for a short circuit in the MAF sensor signal circuit. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary? | -- | ||
10 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
11 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement. Is the action complete? | -- | -- | |
12 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
