Circuit Description
The engine control module (ECM) 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 it converts these into voltage outputs. The ECM sends a 5-volt reference voltage to the MAP sensor. As the manifold pressure changes, the output of MAP sensor also changes. By monitoring the MAP sensor output voltage, the ECM knows the manifold pressure. A low pressure, low voltage, output voltage will be about 1-1.5 volts while the higher pressure, high voltage, output voltage will be about 4.5-4.8 volts at wide open throttle (WOT). The MAP sensor is also used, under certain conditions to measure barometric pressure (BARO), allowing the ECM to make adjustments for different altitude.
Conditions for Setting the DTC
| • | The MAP is less than 12 kPa (1.7 psi). |
| • | No TP sensor fail conditions are present. |
| • | The TP sensor is greater than or equal to 0 percent if the RPM is less than or equal to 1,500. |
| • | The TP sensor is greater than 10 percent if the RPM is greater than 1,500. |
| • | System voltage is greater than 11 volts. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM 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. |
| • | The ECM will substitute a fixed MAP value and use TP sensor to control the fuel delivery. The scan tool will not show defaulted values. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 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. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
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 ECM 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 12 kPa (1.7 psi).
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 Manifold Absolute Pressure Sensor Diagnosis for further diagnosis.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The On-Board Diagnostic System Check prompts the technician to complete some basic checks and store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
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This step will determine 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 malfunctioning or if there is a problem with the ECM or wiring.
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The scan tool may not display 5 volts. The important thing is that the ECM recognizes the voltage as more than 4 volts, indicating the signal circuit are OK. A test light that illuminates indicates a short to ground in the signal circuit.
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A short to ground in the 5-volt reference circuit could also set additional DTCs.
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The replacement ECM must be programmed. Refer to the latest Techline procedure for the ECM reprogramming.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Perform an On-Board Diagnostic System Check. Was the check performed? | -- | Go to Step 2 | ||||||||
Does the scan tool display a MAP less than the specified value? | 12 kPa (1.7 psi) | Go to Step 3 | Go to Step 4 | |||||||
Does the scan tool display MAP greater than the specified value? | 96 kPa (13.9 psi) | Go to Step 5 | Go to Step 6 | |||||||
4 |
Does the scan tool display MAP less than the specified value? | 12 kPa (1.7 psi) | Go to Step 3 | Go to Diagnostic Aids | ||||||
5 | Inspect the MAP sensor harness electrical connector terminals for the following conditions:
Is a repair necessary? | -- | Go to Step 8 | Go to Step 9 | ||||||
Does the scan tool display greater than the specified value? | 90 kPa (13 psi) | Go to Step 7 | Go to Step 12 | |||||||
Inspect the MAP sensor 5-volt reference circuit at terminal C for an open or short to ground. Is a repair necessary? | -- | Go to Step 10 | Go to Step 11 | |||||||
8 | Repair the connection terminals as necessary. Did you complete the repair? | -- | Go to Step 14 | -- | ||||||
9 | Replace the MAP sensor. Did you complete the replacement? | -- | Go to Step 14 | -- | ||||||
10 | Repair the MAP sensor 5-volt reference circuit. Did you complete the repair? | -- | Go to Step 14 | -- | ||||||
Did you complete the replacement? | -- | Go to Step 14 | -- | |||||||
12 | Inspect the MAP sensor signal circuit for the following conditions:
Is a repair necessary? | -- | Go to Step 13 | Go to Step 11 | ||||||
13 | Repair the MAP sensor signal circuit. Refer to Manifold Absolute Pressure Sensor Replacement Is the action complete? | -- | Go to Step 14 | -- | ||||||
14 |
Does the scan tool indicate that this diagnostic has run and passed? | -- | Go to Step 15 | Go to Step 2 | ||||||
15 | Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
