Circuit Description
The manifold absolute pressure (MAP) sensor is mounted to the top rear of the intake manifold. The MAP sensor measures the pressure changes within the intake manifold which is an indication of the engine load. The MAP sensor has a 5.0 volt reference, a ground, and a signal circuit.
The MAP sensor contains a diaphragm which changes the resistance based on pressure. When the manifold pressure is low, high vacuum, the sensor output voltage is low. When the manifold pressure is high the sensor output voltage is high.
The MAP sensor voltage depending on altitude, can range from 1.0-1.5 volts at idle to 4.0-4.9 volts at wide open throttle(WOT).
When the powertrain control module (PCM) senses a signal voltage lower than the normal operating range of the sensor, this diagnostic trouble code (DTC) sets.
Conditions for Running the DTC
| • | No TP sensor DTCs are set. |
| • | The engine is running. |
| • | The TP angle is no more than 0 percent when the engine speed is less than 1,200 RPM. |
| OR |
| • | The TP angle is no more than 20 percent when the engine speed is more than 12,00 RPM. |
Conditions for Setting the DTC
| • | The MAP sensor voltage is less than 0.10 volts. |
| • | All conditions are met for more than 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
| • | The following may cause an intermittent: |
| - | Mis-routed harness |
| - | Rubbed through wire insulation |
| - | Broken wire inside the insulation |
| • | The PCM 5.0 volt reference circuits are internally connected within the PCM. If all the MAP sensor circuits are OK, inspect the EGR circuits for malfunctions. |
| • | For an intermittent, refer to Symptoms . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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If DTC P1635 sets at the same time, this indicates that the 5 voltage reference circuit is either shorted to a ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM. The EGR valve or circuits may be causing this DTC to set. Refer to DTC P1635 5 Volt Reference 1 Circuit for further diagnosis.
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This step determines if the malfunction is present.
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Using the Freeze Frame and Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions such as RPM, load, vehicle speed, temperature, etc. that you observed. This will isolate when the DTC failed.
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The MAP sensor is located under the intake manifold sight shield. If the scan tool displays 5 volts, the MAP sensor signal circuit, 5 volt reference circuit, and the PCM are OK.
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If the scan tool displays 5 volts, the MAP sensor signal circuit and the PCM are OK.
-
Disconnecting the PCM allows using the DMM in order to check the continuity of the circuits. This aids in locating an open or a shorted circuit.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
Did DTC P1635 fail this ignition cycle? | -- | |||||||||
Monitor the MAP sensor voltage on Engine 1 Data List on the scan tool. Is the MAP sensor voltage below the specified value? | 0.2 V | |||||||||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | ||||||||
Is the MAP sensor voltage near the specified value? | 5 V | |||||||||
Is the MAP sensor voltage near the specified value? | 5 V | |||||||||
Did you find the 5 volt reference circuit open or shorted to a ground? | -- | |||||||||
8 |
Did the terminal require replacement? | -- | ||||||||
9 |
Did you find the MAP sensor signal circuit open or shorted to a ground? | -- | ||||||||
10 | Check the MAP sensor signal circuit for a poor connection at the PCM and replace the terminal if necessary. Refer to Connector Repairs in Wiring Systems. Did the terminal require replacement? | -- | ||||||||
11 |
Important: Inspect for poor connections at the MAP sensor before replacing. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |||||||
12 |
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||
13 |
Does the scan tool indicate that this test ran and passed? | -- | ||||||||
14 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
