Circuit Description
The powertrain control module (PCM) uses the manifold absolute pressure (MAP) sensor output voltage in order to assist in controlling the fuel delivery and the ignition timing. The PCM supplies a 5 volt reference signal voltage and a ground circuit to the MAP sensor. As the manifold pressure changes, the output voltage of the sensor also changes. By monitoring the sensor output voltage, the PCM knows the manifold pressure. A lower pressure, or low voltage, output voltage will read between 1.0 to 1.5 volts at idle. While higher pressure, or high voltage, output voltage will read between 4.5 to 4.8 at wide open throttle (WOT). The PCM uses the MAP sensor to record the barometric pressure during an engine start up and at wide open throttle. This allows the PCM to make adjustments for different altitudes.
Conditions for Running the DTC
| • | DTC P0122 or P0123 are 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) illuminates after two ignition cycles with the malfunction present. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers stores this information. |
| • | A history DTC is stored. |
| • | The PCM substitutes a fixed MAP value. The PCM uses the throttle position in order to control the fuel delivery. The scan tool will not show the defaulted value. |
| • | The vehicle will operate in Open Loop when the vehicle is under 5 mph. The vehicle will operate in Closed Loop when the vehicle is over 5 mph. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 3 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. |
| • | A scan tool can clear the DTCs. |
Diagnostic Aids
| Important: After repairs use the scan tool Fuel Trim Reset function in order to reset the Long Term FT to 0 percent. |
| • | With the ignition ON and the engine OFF, the manifold pressure is equal to the atmospheric pressure and the signal voltage will be high. The PCM uses this information as an indication of the altitude of the vehicle. The 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 volts. |
| • | Whenever a DTC P0107 is intermittent, refer to the driveability symptoms tables or to Symptoms for further diagnosis. |
Test Description
The numbers below refer 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 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 may 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 CKP System Variation Learn Procedure for the Crankshaft Position System Variation Learn Procedure .
Step | Action | Values | 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 | |||||||||
3 |
Does the scan tool display a MAP voltage below the specified value? | 0.25 V | Go to Diagnostic Aids | |||||||
Does the MAP voltage read more than the specified value? | 4.7 V | |||||||||
5 | Inspect the MAP sensor connector electrical terminals for the following conditions:
Was a condition found? | -- | ||||||||
Does the scan tool read over the specified value? | 4.0 V | |||||||||
|
Important: The powertrain control module (PCM) uses a single internal 5 volt power supply to supply power to all the engine control components. If one or more component DTCs for voltage low are set, the 5 volt short to ground may originate on that 5 volt supply circuit and affect this DTC.
Does the circuit show continuity? | 0 ohms or above | |||||||||
8 | Repair the faulty connection or terminal. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
9 |
Was a repair necessary? | -- | ||||||||
10 | Repair the short to ground in the MAP 5 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
Repair the open circuit in the MAP 5 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | ||||||||
Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | ||||||||
13 |
Was a condition found? | -- | ||||||||
14 |
Important: The replacement PCM must be programmed. Is the action complete? | -- | -- | |||||||
15 | Repair the MAP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
16 |
Does the scan tool indicate that this diagnostic Ran and Passed? | -- | ||||||||
17 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
