Circuit Description
The 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 (low voltage) output voltage will read between 1.0 to 1.5 volts at idle. While higher pressure (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 Setting the DTC
| • | The MAP is less than 14 kPa. |
| • | The engine speed is less than 1200 RPM. |
| • | The Throttle Position (TP) sensor is greater than 16%. |
| • | The above conditions are met for 0.2 seconds. |
| • | DTC P0122 or P0123 is not set. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) illuminates. |
| • | 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 opeerate 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 malfunction indicator lamp (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. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
Important: After repairs use the scan tool Fuel Trim Reset function in order to reset the long term fuel trim to 128 (0 %).
| • | 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 volt. |
| • | Whenever a DTC P0107 is intermittent, refer to the Driveability Symptoms Tables or to 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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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
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This step determines if DTC P0107 is the result of a hard failure or an intermittent condition.
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Jumpering harness terminals B to C (signal circuit to 5 volts) will determine if the sensor is at fault or if there is a problem with the PCM or wiring.
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The scan tool may not display 5 volts. The important thing is that the PCM recognizes the voltage as more than 4 volts, indicating that the PCM and the MAP signal circuit are OK. A test lamp that illuminates indicates a short to ground in the signal circuit.
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An open or short to ground in the 5V reference circuit could also set additional DTCs.
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Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Reprogram the replacement PCM. Refer to the latest Techline information for programming procedures.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Does the scan tool display 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 MAP sensor voltage below the specified value? | 0.25 V | Go to the Diagnostic Aids | |
5 | Inspect the electrical connectors terminals for poor connections. Was a problem found? | -- | ||
Does the scan tool read greater than the specified value? | 4.0 V | |||
Check the MAP sensor 5 volt reference circuit for an open or a short to ground. Was the problem found? | -- | |||
8 | Repair the connector terminals as necessary. Is the action complete? | -- | -- | |
9 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |
10 | Repair the 5 volt reference circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
12 | Check the MAP sensor signal circuit for an open, short to ground, or a short to sensor ground. Was a problem found? | -- | ||
13 | Repair the MAP sensor signal circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
14 |
Does the scan tool indicate that this diagnostic ran and passed? | 90°-95° C | ||
15 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
