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), 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 active TP sensor DTCs are present. |
| • | The engine has been running for a length of time determined by startup coolant temperature. The length of time ranges from 2 minutes at less than -30°C(-22°F) to 0.5 seconds at more than 30°C(86°F). |
| • | The idle speed is steady. |
| • | Throttle position is below 2%. |
| • | Engine speed is less than 900 RPM. |
Conditions for Setting the DTC
| • | The MAP sensor signal voltage is greater than 4.2 volts. |
| • | The above condition is present for more than 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (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 Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL 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. |
Diagnostic Aids
Check for the following conditions:
| • | With a scan tool, monitor the MAP sensor. If the MAP sensor does not respond to throttle changes, check the 3X reference circuits from the ignition control module to the PCM. |
| If the 3X reference 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. |
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP 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 fault. |
If DTC P0108 cannot be duplicated, the information included in the Freeze Frame/Fail Records data can be useful in determining the conditions are present when the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1108 Diagnostic Chart may isolate the cause of the fault.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Does the scan tool indicate MAP voltage greater than the specified value? | 3.5V | ||
3 |
Does scan tool indicate DTC P0108 failed? | -- | Go to Diagnostic Aids | |
4 |
Does the scan indicate MAP voltage at or near the specified value? | 0V | ||
5 | Probe the sensor ground circuit with a J 35616-200 Test Lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
6 | Test the MAP signal circuit for a short to voltage or a short to the 5 volt reference A circuit. Refer to Wiring Repairs . Did you find and correct the condition? | -- | ||
7 | Inspect for a poor ground circuit connection at the MAP sensor. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | ||
8 | Inspect for a plugged or leaking vacuum supply to the MAP sensor. Was a problem found? | -- | ||
9 | Inspect for a poor MAF sensor ground connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | ||
10 | Test the MAP sensor ground circuit for an open or high resistance. Refer to Wiring Repairs . Did you find and correct the condition? | -- | ||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | -- | ||
12 | Test for a short to voltage on the 5 volt reference A circuit. Refer to Wiring Repairs . Did you find and correct the condition? | -- | ||
13 | Inspect for poor connections at the MAP sensor. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | ||
14 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | -- | |
15 | Repair the faulty vacuum source. Did you complete the repair? | -- | -- | |
16 |
Does the DTC reset? | -- | System OK |
