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.
DTC Descriptor
This diagnostic procedure supports the following DTC.
DTC P0108 MAP Sensor Circuit High Voltage
MAP Correlation
The following table illustrates the differences between the engine conditions, the MAP sensor values, and the engine vacuum:
Engine Condition | MAP kPa | MAP Voltage | Engine Vacuum |
|---|---|---|---|
Idle | Low | Low | High |
Deceleration | Low | Low | High |
Ignition ON, Engine OFF | High | High | Low |
Wide-Open Throttle | High | High | Low |
Conditions for Running the DTC
| • | The engine is operating. |
| • | DTCs P0116, P0117, P0118, P0121, P0122, or P0123, P0125, P0128 are not set. |
| • | The throttle position (TP) angle is above 20 percent when the engine speed is more than 1,000 RPM. |
| OR |
| • | The TP angle is below 18 percent when the engine speed is less than 1,200 RPM. |
Conditions for Setting the DTC
The MAP sensor voltage is more than 4.8 volts for more than 4 seconds.
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
| • | Inspect the MAP sensor vacuum source for leaks, for restrictions, or for poor connections. |
| • | Inspect the engine oil pressure sensor circuits for malfunctions. |
| • | 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 less than the specified value? | 4.9 V | Go to Step 3 | Go to Step 4 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | |
4 |
Is the voltage less than the specified value? | 0.1 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 | Test for shorted terminals and 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 | Test for shorted terminals and 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 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that you have not diagnosed? | -- | System OK | |
