Circuit Description
The DTC P1108 Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent High Voltage diagnostic monitors the MAP sensor response to pressure changes in the intake manifold. The pressure changes occur based on engine load and the throttle valve opening. The MAP sensor has the following circuits:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A 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 PCM receives a low voltage on the signal circuit when manifold vacuum is high at idle or deceleration. The PCM receives a high voltage when manifold vacuum is low at wide open throttle (WOT) or when the ignition is ON and the engine is OFF. The PCM monitors the MAP sensor signal for voltage outside of the normal range and sets a DTC P1108 when the voltage is unusually high.
Engine Condition | MAP kPa | MAP Signal Voltage | Manifold Vacuum |
|---|---|---|---|
Idle | Low | Low | High |
Deceleration | Low | Low | High |
Ignition ON, Engine OFF | High | High | Zero |
Wide-Open Throttle | High | High | Low |
Conditions for Running the DTC
| • | Barometric pressure (BARO) is more than 75 kPa. |
| • | The intake air temperature (IAT) is more than -10°C (14°F). |
| • | The engine coolant temperature (ECT) is more than 80°C (176°F). |
| • | The vehicle speed is detected |
| • | The throttle valve opening is more than a specified value. |
Conditions for Setting the DTC
The MAP sensor signal is greater than 2.7 volts for 1 minute or more.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool Clear DTC Information function. |
Diagnostic Aids
Inspect for the following conditions:
| • | Inspect for an exhaust gas recirculation (EGR) valve that is stuck open. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis . |
| • | Inspect for a restricted exhaust system. Refer to Restricted Exhaust in Engine Exhaust. |
| • | If a DTC P1108 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P1108 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P1108 appears in the Not Ran Since Code Cleared list, the P1108 diagnostic has not yet run. When DTC P1108 does not appear in the Not Ran Since Code Cleared list, the P1108 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P1108 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved. |
An intermittent malfunction may be caused by a fault in the MAP sensor circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
If the DTC P1108 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks for a faulty vacuum supply to the MAP sensor. The scan tool will indicate higher than normal MAP sensor voltage, if the manifold vacuum signal does not reach the MAP sensor vacuum port.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P1108 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P1108 appears in the Not Ran Since Code Cleared list, the DTC P1108 diagnostic has not yet run. When the DTC P1108 does not appear in the Not Ran Since Code Cleared list, the DTC P1108 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P1108 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
Did you perform the Diagnostic System Check -- Engine Controls? | -- | Go to Step 2 | ||||||||
2 |
Is the MAP sensor voltage equal to or more than the specified value? | 2.7 V | Go to Step 4 | Go to Step 3 | ||||||
3 |
Did a DTC P1108 set or was the MAP sensor voltage always more than the specified value? | 2.7 V | Go to Step 4 | Go to Diagnostic Aids | ||||||
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 5 | |||||||
5 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 7 | ||||||
6 |
Is the voltage near the specified value? | 0.0 V | Go to Step 9 | Go to Step 8 | ||||||
7 | Repair the open circuit or poor connection in the MAP sensor ground circuit between the MAP sensor and S106. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- | ||||||
8 |
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 | ||||||
9 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||
10 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||
Does the DTC run and pass? | -- | Go to Step 12 | Go to Step 2 | |||||||
12 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||
