Circuit Description
The manifold absolute pressure (MAP) sensor is mounted to the 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 (low vacuum) the sensor output voltage is high.
The MAP sensor voltage (depending on altitude) can range from 1.0-1.5 volts at idle (high vacuum) to 4.0-4.9 volts at wide open throttle (low vacuum).
When the PCM senses a signal voltage higher than the normal operating range of the sensor, this DTC sets.
Conditions for Running the DTC
| • | No throttle position (TP) sensor DTCs set. |
| • | The engine is operating. |
| • | The TP sensor angle is less than 5 percent when the engine speed is no more than 1,000 RPM. |
| OR |
| • | The TP sensor angle is less than 18 percent when engine speed is more than 1,000 RPM. |
Conditions for Setting the DTC
| • | The MAP sensor voltage is more than 4.3 volts. |
| • | All conditions met for more than 4 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/replacing the PCM.
Ensure that the gaskets are installed correctly. The gaskets prevent
contaminant intrusion into the PCM. • For any test that requires probing the PCM or component
harness connectors, use the J 35616
connector test adapter kit . Using this kit prevents
any damage to the harness connector terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
The PCM 5.0 volt reference circuits are internally connected within the PCM. If all the MAP sensor circuits are OK, inspect the following component/circuits for malfunctions:
| • | Throttle position sensor |
| • | EGR valve |
For an intermittent, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the malfunction is present.
-
Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or 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 and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.
-
This step verifies whether the signal circuit is shorted to a voltage.
-
This step verifies whether a ground circuit is available at the MAP sensor.
-
The MAP sensor is difficult to remove. Twist the MAP sensor forward and pull up. This forward motion clears the retaining clip. Remove the MAP sensor and verify if vacuum is available to the sensor. Also, inspect the MAP sensor seal for nicks and cuts.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Did DTC P1635 and P1639 fail this ignition cycle? | -- | |||
|
Important: If the engine idle is rough, unstable or incorrect, repair the idle condition before using this table; refer to Symptoms . Monitor the MAP sensor voltage on the Engine 1 Data List on the scan tool. Is the MAP sensor voltage above the specified value? | 4.3V | |||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | ||
Is the MAP sensor voltage below the specified value? | 1V | |||
Probe the sensor ground circuit with the J 35616-200 test lamp connected to B+. Refer to Probing Electrical Connectors in Wiring Systems. Is the test lamp illuminated? | -- | |||
7 |
Is the MAP sensor signal circuit shorted? | -- | ||
8 | Measure the voltage at the 5 volt reference circuit to the battery ground using the DMM. Is the voltage near the specified value? | 5V | ||
Inspect for a plugged or leaking vacuum supply to the MAP sensor. Is the vacuum supply OK? | -- | |||
10 |
Did you find and correct the condition? | 2ohms | ||
11 |
Did you find and correct the condition? | -- | ||
12 |
Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
13 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |
14 | Repair the faulty vacuum supply. Is the action complete? | -- | -- | |
15 | Repair the 5 volt reference circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems . Is the action complete? | -- | -- | |
16 |
Does the scan tool indicate that this test ran and passed? | -- | ||
17 | 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 |
