P1408

DTC P1408 Manifold Absolute Pressure (MAP) Sensor Circuit:

Manifold Absolute Pressure (MAP) Sensor Circuit:

CIRCUIT DESCRIPTION

The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure (vacuum). The Engine Control Module (ECM) provides a 5 volt reference voltage to the MAP sensor. The change in the pressure, that results from engine load and RPM changes, is converted into a voltage input that is monitored by the ECM. By monitoring the sensor output voltage, the ECM can detect the manifold pressure change when the EGR valve is operated and judges the EGR flow to be faulty when this pressure change is excessively large or small.


CONDITIONS FOR SETTING THE DTC

Signal voltage is greater than 4.8 volts.


- Engine coolant temperature is greater than 45°C (113°F).

- Intake air temperature is greater than 5°C (41°F).

- Throttle position is less than 100.

Or

- Signal voltage is less than 0.2 volts.

- Engine coolant temperature is greater than 45°C (113°F).

- intake air temperature is greater than 5°C (41°F).

- Throttle position is greater than 5°.


ACTION TAKEN WHEN THE DTC SETS


- The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC

- The MIL will turn "OFF" after three consecutive drive cycles without a fault present.

- A DTC will clear after 40 consecutive warm-up cycles without a fault.

- DTC(s) can be cleared by using a scan tool or by disconnecting the ECM battery feed.


DIAGNOSTIC AIDS


Check the following conditions:


- Poor connection at ECM. Inspect harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

- Check for proper vacuum routing, spilt, or pinch vacuum lines.

- Damaged harness. Inspect the wiring harness for damage.

If DTC P1408 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions since the DTC was last set. This may assist in determining how often the DTC sets.


If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams.


TEST DESCRIPTION


Number(s) below refer to the step number(s) on the Diagnostic Table.


1. The Engine OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

3. Review Freeze Frame data to determine when the DTC set. Always record this information.

7. By manually applying vacuum to the MAP sensor, the signal voltage should slowly decrease.