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 will set.
Conditions for Running the DTC
| • | DTCs P0122 or P0123 are not set. |
| • | The throttle position (TP) is less than 15 percent. |
| • | The vehicle speed is less than 2 km/h (1 mph). |
| • | The engine run time is more than 20-40 seconds. |
Conditions for Setting the DTC
The MAP sensor voltage is more than 4.2 volts for at least 1 second.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM will store the conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
| • | A history DTC is stored. |
| • | The PCM will substitute a defaulted MAP value to control the fuel delivery. The scan tool will not show the defaulted value. |
| • | The engine will operate in Open Loop when the vehicle is traveling under 8 km/h (5 mph). |
| • | The engine will operate in Closed Loop when the vehicle is traveling over 8 km/h (5 mph). |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the malfunction indicator lamp (MIL) OFF after three consecutive drive trips that the diagnostic runs and passes. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
| • | The 5-volt reference circuits used by the various engine control components are internally connected in the PCM. If a component's 5-volt reference circuit is shorted to voltage, the other 5-volt reference circuits may be affected. |
| • | Inspect the MAP sensor vacuum source for leaks, restrictions, or poor connections. |
| • | This DTC may set as the result of a misfire. |
| • | If an intermittent condition exists, refer to Intermittent Conditions . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the MAP sensor voltage is greater than the specified value? | 4.2 V | Go to Step 4 | Go to Step 3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | |
4 |
Does the scan tool indicate that the MAP sensor voltage is less than the specified value? | 0.2 V | Go to Step 5 | Go to Step 7 |
5 | Measure the voltage from the 5-volt reference circuit to the low reference circuit at the MAP sensor electrical connector. Does the voltage measure within the specified value range? | 4.7-5.2 V | Go to Step 10 | Go to Step 6 |
6 | Does the voltage measure more than the specified value? | 5.2 V | Go to Step 9 | Go to Step 8 |
7 | Test the signal circuit of the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
8 | Test the low reference circuit of the MAP sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
9 | Test the 5-volt reference circuit of the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
10 | Inspect for poor connections at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 |
11 | Inspect for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 |
12 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 |
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
