Circuit Description
The manifold absolute pressure (MAP) sensor responds 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 powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The PCM 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 PCM monitors the MAP sensor signal for voltage outside of the normal range.
If the PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage
Conditions for Running the DTC
| • | The engine has been running for a length of time that is determined by the startup coolant temperature. The length of time ranges from 5.5 minutes at less than -30°C (-22°F) to one second at more than 30°C (86°F). |
| • | DTC P0068, P0120, P0220, P1516, P2101, P2108, P2120, P2125, P2135, P2138 are not set. |
| • | The throttle angle is less than 2 percent when the engine speed is less than 3,000 RPM. |
| OR |
| • | The throttle angle is less than 30 percent when the engine speed is more than 3,000 RPM. |
Conditions for Setting the DTC
| • | The PCM detects that the MAP sensor voltage is more than 4.3 volts for more than 3 seconds. |
| • | This diagnostic runs continuously. |
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 due to poor idle characteristics. A possible cause may be uncontrolled fueling due to an open or high resistance in the heated oxygen sensor (HO2S) 1 low signal circuit. Before replacing any component, ensure that this condition does not exist.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 |
Is the voltage more than the specified value? | 4.3 V | Go to Step 4 | Go to Step 3 | ||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||
4 | Inspect the manifold absolute pressure (MAP) sensor vacuum source for the following conditions:
Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 5 | ||||||
5 | Monitor the DTC Information with the scan tool. Is DTC P0641 also set? | -- | Go to Step 9 | Go to Step 6 | ||||||
6 | Test for an intermittent and for a poor connection at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 7 | ||||||
7 |
Is the voltage less than the specified value? | 0.1 V | Go to Step 8 | Go to Step 10 | ||||||
8 |
Is the voltage more than the specified value? | 0.2 V | Go to Step 11 | Go to Step 13 | ||||||
9 |
Is the voltage less than the specified value? | 0.1 V | Go to DTC P0641 | Go to Step 10 | ||||||
10 | Test the MAP sensor signal circuit between the powertrain control module (PCM) and the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||
11 | Test the low reference circuit between the PCM and the MAP sensor for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 12 | ||||||
12 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||
13 | Test the heated oxygen sensor (HO2S) 1 low signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 | ||||||
14 | Test the HO2S 1 low signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||
15 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||
16 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||
17 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 18 | ||||||
18 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
