Circuit Description
The manifold absolute pressure (MAP) sensor responds to changes in the intake manifold pressure. The powertrain control module (PCM) supplies a 5 volt reference and a ground for the MAP sensor. The MAP sensor provides a signal to the PCM relative to pressure changes in the manifold. The MAP sensor signal voltage to the PCM varies from below 2 volts at idle (low manifold absolute pressure - high vacuum) to above 4 volts with the key on and engine not running or at wide open throttle. The PCM monitors the MAP signals for voltages outside the normal range of the MAP sensor. If the PCM detects a MAP signal voltage that is excessively high, DTC P0108 is set.
Conditions for Running the DTC
| • | No TP sensor DTCs are present. |
| • | The engine has run for a length of time that is determined by the startup coolant temperature. The length of time ranges from 2 minutes at less than -30° C (-22° F) to 0.5 second at more than 30°C (86°F). |
| • | The idle speed is steady. |
| • | The throttle position is below 2%. |
| • | The engine speed is less than 900 RPM. |
Conditions for Setting the DTC
| • | The MAP sensor signal voltage is more than 4.2 volts. |
| • | The above conditions are present for longer than 200 3X reference periods. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed. |
| • | The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL off during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Inspect for the following conditions:
| • | A faulty connection at the PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. |
| • | Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display indicates the location of the malfunction. |
If DTC P0108 cannot be duplicated, the information included in the Fail Records data may be useful in determining since the DTC was last set. If the DTC occurs intermittently, performing the DTC P1108 Diagnostic Chart may isolate the cause of the malfunction.
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table:
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Is the MAP voltage more than the specified value? | 3.5 V | ||
3 |
Does the scan tool indicate DTC P0108 failed? | -- | Go to Diagnostic Aids | |
4 |
Is the voltage at the specified value? | 0 V | ||
5 | Use a test lamp connected to B+ in order to probe the MAP sensor ground circuit. Does the test lamp illuminate? | -- | ||
6 |
Did you complete the repair? | -- | ||
7 |
Was a problem found? | -- | ||
8 | Inspect for a plugged or leaking vacuum supply to the MAP sensor. Was a problem found? | -- | ||
9 |
Was a problem found? | -- | ||
10 |
Was a problem found? | 5 ohms | ||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- | ||
12 |
Was a problem found? | -- | ||
13 | Test for faulty electrical connections at the MAP sensor and replace any terminals as necessary. Refer to Connector Repairs in Wiring Systems. Was a problem found? | -- | ||
14 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the repair? | -- | -- | |
15 | Repair the malfunctioning vacuum source. Did you complete the repair? | -- | -- | |
16 |
Does the scan tool indicate DTC P0108 failed? | -- | System OK |
