DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage. Isuzu S/T Isuzu

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 4WD 🢒 DTC 🢒 DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage

Engine Controls Components
Cell 20: MAP, IAT, TPS and ECT Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM uses the Manifold Absolute Pressure (MAP) sensor output voltage in order to assist in controlling the fuel delivery and the ignition timing. The PCM supplies a 5 volt reference signal voltage and a ground circuit to the MAP sensor. As the manifold pressure changes, the output voltage of the sensor also changes. By monitoring the sensor output voltage, the PCM knows the manifold pressure. A lower pressure (low voltage) output voltage will read between 1.0 to 1.5 volts at idle. While higher pressure (high voltage) output voltage will read between 4.5 to 4.8 at Wide Open Throttle (WOT). The PCM uses the MAP sensor to record the barometric pressure during an engine start up and at wide open throttle. This allows the PCM to make adjustments for different altitudes.

Conditions for Running the DTC

•	DTCs P0122 or P0123 are not set.

•	The throttle position (TP) sensor is less than 12 percent.

•	The vehicle speed sensor is less than 2 km/h (1 mph).

•	The engine run time is more than 20 to 40 seconds.

Conditions for Setting the DTC

•	The MAP sensor is more than 82 kPa.

•	The above condition is met for at least 1.25 seconds.

Action Taken When the DTC Sets

•	The Malfunction Indicator Lamp (MIL) illuminates after two igntion cycles with the malfunction present.

•	The PCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers stores this information.

•	A history DTC is stored.

•	The PCM substitutes a fixed MAP value. The PCM uses the throttle position in order to control the fuel delivery. The scan tool will not show the defaulted value.

•	The vehicle will operate in Open Loop when the vehicle is under 5 mph. The vehicle will operate in Closed Loop when the vehicle is over 5 mph.

Conditions for Clearing the MIL/DTC

•	The malfunction indicator lamp (MIL) will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.

•	A history DTC will clear after 40 consecutive warm up cycles without a fault.

•	Use a scan tool to clear the DTCs.

Diagnostic Aids

Notice:

•	After repairs use the scan tool Fuel Trim Reset function to reset long term fuel trim to 128 (0 percent).

•	Whenever a misfire is present, repair the cause of the misfire before using this table. The misfire counters may be used to determine which cylinders are misfiring.

With the ignition ON and the engine off, the manifold pressure is equal to the atmospheric pressure and the signal voltage will be high. The PCM uses this information as an indication of the altitude of the vehicle. A comparison of this reading with a known good vehicle with the same sensor is a good way to check the accuracy of a suspect sensor. Readings should be the same ±0.4 volt.

Whenever a DTC P0108 is intermittent, refer to Driveability Symptoms or to Manifold Absolute Pressure Sensor Output Diagnosis for further diagnosis.

Test Description

The number(s) below refer(s) to the step number(s) on the Diagnostic Table.

The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.

This step will determine if the DTC P0108 is the result of a hard malfunction or an intermittent condition.

This step simulates the conditions for a DTC P0107. If the PCM recognizes the change, the PCM, the 5.0 volt reference and the MAP sensor signal circuits are OK.

This step looks for an open in the MAP sensor ground circuit.

When the MAP sensor signal circuit is shorted to battery voltage, the TP will display above 0 percent at all times and the A/C High Side will display high. The vehicle will also remain in Open Loop.

The MAP sensor vacuum source should only supply vacuum to the MAP sensor. Check the vacuum port for a restriction caused by casting flash.

Important: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

Disconnect all of the sensors that use a 5.0 volt reference one at a time while monitoring the short on the 5.0 volt reference circuit. Replace any sensor that may have caused the short on the 5.0 volt reference circuit.

Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming and Crankshaft Position System Variation Learn for the crankshaft position system variation learn procedure.

DTC P0108-Manifold Absolute Pressure (MAP) Circuit-High Voltage

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Install a scan tool.
Start the engine.
Idle the engine.

Does the scan tool display a MAP voltage of the specified value or more?

4.0 V

Go to Step 3

Go to Step 4

Turn OFF the ignition switch.
Disconnect the MAP sensor electrical connector.
Turn ON the ignition switch leaving the engine OFF.

Does the scan tool display a MAP voltage of the specified value or less?

1.0 V

Go to Step 5

Go to Step 6

Turn ON the ignition switch leaving the engine OFF.
Review the Freeze Frame data and record the parameters.
Start the engine.
Operate the vehicle within the freeze frame conditions and Conditions For Setting The DTC as specified in the supporting text.

Does the scan tool display a MAP voltage of the specified value or more?

4.0 V

Go to Step 3

Go to Diagnostic Aids

Connect a test light to battery voltage.
Probe the MAP sensor ground circuit terminal.

Does the test light illuminate?

Go to Step 7

Go to Step 11

Turn OFF the ignition switch.
Check the MAP sensor signal circuit for a short to voltage.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 14

Go to Step 12

Connect a DMM to ground.
Probe the 5.0 volt reference circuit.

Does the DMM display near the specified value?

5.0 V

Go to Step 8

Go to Step 9

Turn OFF the ignition switch.
Check the MAP sensor vacuum source for the following conditions:

•

Plugged

•

Leaking

Was a problem found?

Go to Step 10

Go to Step 13

Turn OFF the ignition switch.
Check the 5.0 volt reference circuit for a short to battery voltage.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 14

Go to Step 12

Repair the vacuum source as necessary.

Is the action complete?

Go to Step 14

Turn OFF the ignition switch.
Check for the following conditions in the MAP sensor ground circuit:

•	Open circuit

•	Poor electrical connection(s)

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 14

Go to Step 12

Replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

Go to Step 14

Turn OFF the ignition switch.
Replace the MAP sensor. Refer to the Manifold Absolute Pressure Sensor Replacement .

Is the action complete?

Go to Step 14

Using the scan tool, clear the DTCs.
Start the engine.
Idle the engine at the normal operating temperature.
Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

Go to Step 15

Go to Step 2

Check to see if any additional DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

Go to applicable DTC table

System OK