DTC P0108. Saturn L300/LW300 2003

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2003 🢒 L300/LW300 🢒 DTC 🢒 DTC P0108

Engine Controls Component Views
Engine Controls Schematics

Circuit Description

The manifold absolute pressure (MAP) sensor transducer that varies resistance according to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits:

•	5-volt reference circuit

•	Low reference circuit

•	MAP sensor signal circuit

The engine control module (ECM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The ECM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the ECM on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The ECM supplies a bias voltage measuring between 4-6 volts on the MAP sensor signal circuit. The ECM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The ECM should detect a high signal voltage at a high MAP, such as the ignition is ON, with the engine OFF, or at a wide open throttle (WOT). The MAP sensor is also used in order to determine the barometric pressure (BARO). This occurs when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The ECM monitors the MAP sensor signal for voltage outside of the normal range.

If the ECM detects a MAP sensor signal voltage that is excessively high, DTC P0108 sets.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The MAP sensor voltage is more than 4.88 volts for more than 1 second.

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

•	This DTC may set as the result of a misfire.

•	The ECM supplies voltage to various components using three separate 5-volt reference circuits. They are designated A, B, and C.

Through three terminals on the ECM, the 5-volt reference A circuit is distributed to the following components:

-	One circuit supplies voltage to the accelerator pedal position (APP) sensor 1.

-	Another circuit is spliced, and supplies voltage to the air conditioning (A/C) pressure sensor and the fuel tank pressure (FTP) sensor.

-	The last circuit is spliced through a 5-volt reference splice pack, and supplies voltage to the camshaft position (CMP) sensor. The mass air flow (MAF) sensor, the MAP sensor, and the exhaust gas recirculation (ERG) valve.

-	A circuit short or component failure that causes the 5-volt reference A system voltage to be pulled low or high, may affect any of the components that receive voltage from the 5-volt reference A circuit.

•	The low reference circuit of the MAP sensor is spliced together, through a low reference splice pack, to the low reference circuits of the following components:

-	CMP sensor

EGR valve

-	MAF sensor

-	Engine coolant temperature (ECT) sensor

-	Intake air temperature (IAT) sensor

-	Throttle position (TP) sensor 1

-	TP sensor 2

From the low reference splice pack, one circuit is connected to the ECM where it is grounded.

If any of the low reference circuits become shorted to voltage, the voltage will back feed through the MAP sensor affecting the 5-volt reference A system voltage, and damage to the ECM may occur.

If this DTC is determined to be intermittent, refer to Intermittent Conditions .

Test Description

The number below refers to the step number on the diagnostic table.

This step determines if the 5-volt reference A system voltage is high.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Connect End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Attempt to start the engine.

Does the engine start and run?

Go to Step 4

Go to Step 3

Turn ON the ignition, with the engine OFF.
Observe the manifold absolute pressure (MAP) parameter with a scan tool.

Is the pressure more than the specified value?

105 kPa

Go to Step 6

Go to Step 5

Observe the MAP parameter with a scan tool.

Is the voltage more than the specified value?

4.88 V

Go to Step 6

Go to Step 5

Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 90 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records.

Did the DTC fail this ignition?

Go to Step 6

Go to Diagnostic Aids

Test for an intermittent and for a poor connection at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?