Circuit Description
The PCM uses the Manifold Absolute Pressure (MAP) sensor to control the fuel delivery and the ignition timing. The MAP sensor measures the changes in the intake manifold pressure which results from engine load (intake manifold vacuum) and the RPM changes; and converts these into a voltage outputs. The Powertrain Control Module (PCM) sends a 5 volt reference voltage to the MAP sensor. As the manifold pressure changes, the output voltage of the MAP sensor also changes. By monitoring the MAP sensor output voltage, the PCM knows the manifold pressure. A lower pressure (low voltage) output voltage will be about 1.0 to 1.5 volts at idle. While higher pressures (high voltage) output voltage will be about 4.5 to 4.8 volts at Wide Open Throttle (WOT). The MAP sensor is also used, under certain conditions, to measure barometric pressure, allowing the PCM to make adjustments for different altitudes.
Conditions for Running the DTC
| • | DTC P0122 or P0123 is not set. |
| • | The engine speed is less than 1000 RPM. |
| Or |
| The engine speed is more than 1000 RPM and the Throttle Position (TP) sensor is more than 15 percent. |
Conditions for Setting the DTC
| • | The MAP is less than 11.8 kPa. |
| • | The above conditions are met for at least 6.25 seconds. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The Powertrain Control Module (PCM) will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
| • | Coolant fan turns ON. |
| • | The PCM will substitute a fixed MAP value and use Throttle Position (TP) to control the fuel delivery (scan tool will not show defaulted value.) |
| • | The vehicle will operate in Open Loop when the vehicle is under 8 km/h (5 mph). The vehicle will operate in Closed Loop when the vehicle is over 8 km/h (5 mph). |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
With the ignition switch ON and the engine stopped, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the PCM as an indication of vehicle altitude. Comparison of this reading with a known good vehicle with the same sensor is a good way to check the accuracy of a suspect sensor. Readings should be the same +/- 0.4 volt.
Important: After repairs use the scan tool Fuel Trim Reset function to reset long term fuel trim to 128 (0 percent).
If a DTC P0107 is intermittent, refer to Symptoms or to the Manifold Absolute Pressure Sensor Output Diagnosis for further diagnosis.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the DTC P0107 is the result of a hard malfunction or an intermittent condition.
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Connecting a Jumper wire into the connector terminals B to C (signal circuit to the 5.0 volts circuit) will determine if the MAP sensor is malfunctioning or if there is a problem with the PCM or the wiring.
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The scan tool may not display 5.0 volts. The important thing is that the PCM recognizes the voltage as more than 4.0 volts, indicating that the PCM and the MAP sensor signal circuit are OK. A test lamp that illuminates indicates a short to ground in the signal circuit.
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Important: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.
An open or short to ground in the 5.0 volt reference circuit could also set additional DTCs.
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The MAP sensor vacuum source should be thoroughly checked for restrictions. A drill bit can be used to clean out any casting flash that may exist in the manifold vacuum port.
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Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn procedure.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||
Does the scan tool display the MAP voltage below the specified value? | 0.25 V | |||||||||
Does the MAP voltage measure more than the specified value? | 4.7 V | |||||||||
4 |
Does the MAP voltage measure below the specified value? | 0.25 V | Go to Diagnostic Aids | |||||||
5 |
Did you find a problem? | -- | ||||||||
Does the MAP voltage measure over the specified value? | 4.0 V | |||||||||
|
Important:: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.
Did you find a problem? | -- | |||||||||
8 | Repair the connection as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
9 | Replace the MAP sensor. Refer to the Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||
10 | Repair the MAP sensor 5.0 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
Did you find and correct the condition? | -- | |||||||||
Important:: The replacement PCM must be programmed and the Crankshaft Position Variation procedure must be performed. Did you complete the replacement? | -- | -- | ||||||||
13 |
Did you find a problem? | -- | ||||||||
14 | Repair the MAP sensor signal circuit. Refer to Wiring Repairs In Wiring Systems. Did you complete the repair? | -- | -- | |||||||
15 |
Does the DTC reset? | -- | System OK |
