P0108
DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage
Circuit Description
The PCM uses the manifold absolute pressure (MAP) sensor output voltage to control 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 can detect the manifold pressure. A lower pressure (low voltage) output will range between 1.0 - 1.5 volts at idle. While a higher pressure (high voltage) output will range between 4.5 - 4.8 volts at wide open throttle (WOT). The PCM uses the MAP sensor to record the barometric pressure during engine start up and at wide open throttle. This allows the PCM to make adjustments for different altitudes.
Conditions for Running the DTC
- There are not any active TP DTCs.
- The throttle position (TP) sensor reading is less than 12 percent.
- The vehicle speed sensor (VSS) reading is less than 2 kph (1 mph).
- The engine has been running for more than 20 - 40 seconds.
Conditions for Setting the DTC
- The MAP sensor reading is more than 3.80 V (82 kPa)..
- The above conditions are met for at least 1.25 seconds.
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool's Freeze Frame and Failure Records.
Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22° C (40° F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70° C (158° F) during the same ignition cycle.
- Use the scan tool Clear Information function
Diagnostic Aids
NOTE:
- After repairs use the scan tool Fuel Trim Reset function to reset long term fuel trim to 128 (0%).
- 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 is misfiring.
- With the ignition ON and the engine OFF, the manifold pressure is equal to the atmospheric pressure and the MAP sensor signal voltage is high. The PCM uses this voltage reading to determine the altitude of the vehicle. The comparison of this reading with a reading from a known good vehicle using the same sensor is a good way to verify the accuracy of a suspect sensor. Readings should be the same to within a range of 0.4 volt.
Whenever a DTC P0108 is intermittent, refer to Symptoms or to MAP Sensor Output Diagnosis for further diagnosis.
Steps 1 - 5:
Steps 6 - 9:
Steps 10 - 14:
Step 15:
Test Description
The numbers below refers to the step numbers on the Diagnostic Table.
1. 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.
2. This step will determine if the DTC P0108 is the result of a hard malfunction or an intermittent condition.
3. 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.
5. This step looks for an open in the MAP sensor ground circuit.
6. 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.
8. The MAP sensor vacuum source should only supply vacuum to the MAP sensor. Inspect the vacuum port for a restriction caused by casting flash.
9. 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 volt reference circuit to ground or battery voltage, the other 5 volt reference circuits will also have a low or high voltage.
Disconnect all of the sensors that use a 5 volt reference one at a time while monitoring the short on the 5 volt reference circuit. Replace any sensor that may have caused the short on the 5 volt reference circuit.
12. Program 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.