Circuit Description
The manifold absolute pressure (MAP) sensor measures the change in the intake manifold pressure. The powertrain control module (PCM) provides a 5 volt reference voltage to the MAP sensor. The MAP sensor changes the reference voltage in response to changes in the engine load and in the engine speed. The PCM monitors the MAP sensor voltage. A low voltage reading at the PCM indicates low manifold pressure. A high voltage reading at the PCM indicates high manifold pressure.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | A high voltage input at the PCM indicates that manifold absolute pressure is 130 kPa or more. |
| • | The above condition is met for at least 0.5 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time that the diagnostic fails. This information is stored in the Freeze Frame buffer. |
| • | The PCM enters the Fail-Safe mode and monitors the TP sensor and the engine speed inputs. The idle speed feedback control and the EVAP purge control are stopped. |
Conditions for Clearing the DTC
| • | The MIL turns OFF after 3 consecutive trips during which the diagnostic runs, and a fault is not detected. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the Clear DTC Information function of the scan tool, or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
Check for any of the following conditions:
| • | Check for a leak in the vacuum passage to the MAP sensor. |
| • | If DTC P0108, DTC P0113, DTC P0118, and DTC P0123 are set together, the cause could be an open ground circuit. |
| • | A short to voltage in the 5 volt reference circuit can set DTC P0108. |
| • | A faulty electrical connection to the PCM. |
An intermittent malfunction may be caused by a fault in the MAP sensor electrical circuit. Inspect the wiring harness and the components for any of the following conditions:
| • | Backed out terminals. |
| • | Incorrect mating of terminals. |
| • | Broken electrical connector locks. |
| • | Incorrectly formed terminals or damaged terminals. |
| • | Faulty terminal-to-wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, of splices, or of terminals. |
If DTC P0108 cannot be duplicated, the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.
Use the following MAP Conversion table in order to view the relationship between manifold pressure (vacuum), MAP sensor kPa and MAP sensor circuit voltage as displayed on the scan tool.
Manifold Pressure | MAP kPa Display | MAP Volts Display |
|---|---|---|
Sea Level | 99 | 4.75 |
5 in Hg | 82 | 3.93 |
10 in Hg | 64 | 3.07 |
15 in Hg | 48 | 2.30 |
20 in Hg | 30 | 1.44 |
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD system check 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 determines that the fault is present.
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This step checks for the correct input circuit voltage. The scan tool MAP sensor voltage display will indicate 6.99 volts with the MAP sensor disconnected (open in the sensor input circuit). This is caused by the scan tool software and should be considered normal. Ignore the scan tool voltage and use the DMM for all voltage checks when diagnosing a DTC P0108.
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This step checks for an open in the MAP sensor ground circuit.
-
Check for an open in the ground circuit between the sensor and splice S164. If the fault in the ground circuit is between the PCM and the splice, other DTCs would be set.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic System Check? | -- | |||
Is the MAP sensor display at or above the specified value? | 130 kPa | |||
3 |
Is the MAP sensor display above the specified value? | 130 kPa | Go to Diagnostic Aids | |
Is the voltage within the specified value? | 4.9 to 5.0 volts | |||
5 |
Was a repair necessary? | -- | ||
6 |
Was a repair necessary? | -- | ||
Measure the voltage from the MAP sensor signal circuit to the MAP sensor ground circuit (harness side) with the DMM. Is the voltage between the specified value? | 4.9 to 5.0 volts | |||
Was a repair necessary? | -- | |||
9 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |
10 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
11 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
