Circuit Description
The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). The MAP sensor signal voltage to the PCM varies from below 2 volts at idle (high vacuum) to above 4 volts with the key ON, engine not running or at wide open throttle (low vacuum).
The MAP sensor is used to determine manifold pressure changes while the linear EGR flow test diagnostic is being run refer to, DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient , to determine engine vacuum level for other diagnostics and to determine barometric pressure (BARO). 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 will be set.
Conditions for Running the DTC
| • | No TP sensor DTCs present. |
| • | Engine has been running for a length of time that is determined by 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). |
| • | Idle speed is steady. |
| • | Throttle position below 2 percent. |
| • | 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 more than 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
| • | Monitor the MAP sensor using the scan tool and verify the following conditions: |
| - | If the MAP sensor does not respond to throttle changes, check the 3X circuits from the ignition control module to the PCM. |
| - | If the 3X signal is lost the PCM will only update the MAP sensor reading once per key cycle, when the engine is first started. |
| - | Depending on where the MAP sensor voltage, high voltage or low voltage, is when the engine is started, the high or low voltage MAP sensor DTCs will set. |
| • | Inspect for the following conditions: |
| - | Poor connection at PCM |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection--Use a corresponding mating terminal to check for proper terminal tension. |
| - | Damaged harness--If the harness appears to be OK, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction. Refer to Wiring Repairs . |
| • | If DTC P0108 cannot be duplicated, the information included in the Fail Records data can 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 fault. |
Test Description
The number below refers to the step number on the diagnostic table:
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
2 |
Important:: If DTC P1635 5 Volt Reference Circuit is set, perform that diagnostic first.
Does the voltage measure more than the specified value? | 4.2 V | ||
3 |
Does the DTC reset? | -- | Go to Diagnostic Aids | |
4 |
Does the voltage measure at the specified value? | 0 V | ||
5 | Inspect for a plugged or leaking vacuum supply to the MAP sensor. Did you find and correct the condition? | |||
6 | Test the ground circuit of the MAP sensor for continuity. Refer to Circuit Testing in Wiring Systems. If a problem is found, repair as necessary. Did you find and correct the condition? | -- | ||
7 | Test the signal circuit of the MAP sensor for a short to voltage or short to 5 volt reference A circuit. If a problem is found, refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
8 | Inspect the ground circuit of the MAP sensor at the PCM for a poor connection at the harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
9 | Inspect the ground circuit of the MAP sensor at the MAP sensor for poor connections at the harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
10 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | -- | |
|
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
12 |
Does the DTC reset? | -- | System OK |
