Circuit Description
The Powertrain Control Module (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, or intake manifold vacuum, and the RPM changes, and converts these into 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, or low voltage, output voltage will be approximately 1.0 to 1.5 volts at idle. Higher pressures, or higher voltage, output voltage will be approximately 4.5 to 4.8 volts at wide open throttle (WOT). The MAP sensor is also used to measure barometric pressure, allowing the PCM to make adjustments for different altitudes.
Conditions for Setting the DTC
| • | The engine speed is less than 1000 RPM. |
| Or |
| • | The engine speed is greater than 1000 RPM and the Throttle Position (TP) sensor is greater than 15%. |
| • | The MAP is less than 11.8 kPa. |
| • | The above conditions are met for at least 6.25 seconds. |
| • | DTC P0122 or P0123 is not set. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate. |
| • | 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. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
Important: After repairs use the scan tool Fuel Trim Reset function to reset long term fuel trim to 128 (0%).
With the ignition 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 ± .4 volt.
If a DTC P0107 is intermittent, refer to Symptoms or to Manifold Absolute Pressure Sensor Output Diagnosis for further diagnosis.
Test Description
The numbers below refers to the step numbers on the Diagnostic Table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
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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 light 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. Refer to the latest Techline information for PCM programming and Crankshaft Position System Variation Learn .
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
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 read more than the specified value? | 4.7 V | |||||||||
4 |
Does the scan tool display a MAP voltage below the specified value? | 0.25 V | Go to Diagnostic Aids | |||||||
5 |
Was a problem found? | -- | ||||||||
Does the scan tool read over the specified value? | 4.0 V | |||||||||
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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.
Was a problem found? | -- | |||||||||
8 | Repair the electrical connection terminal(s). Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
9 | Replace the MAP sensor. Refer to the Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |||||||
10 | Repair the MAP sensor 5.0 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
Was a repair necessary? | -- | |||||||||
Is the action complete? | -- | -- | ||||||||
13 |
Was a problem found? | -- | ||||||||
14 | Repair the MAP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
15 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||||||||
16 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
