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.
Conditions for Running the DTC
| • | DTC 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 40 seconds. |
Conditions for Setting the DTC
The PCM detects that the MAP sensor voltage is more than 4.2 volts for more than 1 second.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
| • | The PCM will substitute a default 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 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
| • | The 5-volt reference circuits used by the various engine control components are internally connected in the PCM. If a 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: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Is the voltage more 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 Intermittent Conditions | |||||||
4 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 5 | ||||||
5 |
Is DTC P1639 also set? | -- | Go to Step 8 | Go to Step 6 | ||||||
6 |
Is the voltage less than the specified value? | 0.2 V | Go to Step 7 | Go to Step 9 | ||||||
7 |
Is the voltage more than the specified value? | 0.2 V | Go to Step 10 | Go to Step 11 | ||||||
8 |
Is the voltage less than the specified value? | 0.2 V | Go to DTC P1639 | Go to Step 9 | ||||||
9 | Test the MAP sensor signal circuit between the PCM and 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 15 | Go to Step 14 | ||||||
10 | Test the low reference circuit between the PCM and the MAP sensor for high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||||
11 | Inspect for an intermittent and for a poor connection 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 15 | Go to Step 13 | ||||||
12 | Inspect for an intermittent and for a poor connection 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 15 | Go to Step 14 | ||||||
13 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
15 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 16 | ||||||
16 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
