Manifold Pressure/Vacuum Sensor: Description and Operation

PURPOSE
This sensor measures manifold absolute pressure and ambient barometric pressure within the manifold.

OPERATION
The MAP sensor provides a 0 to 5-volt signal to Powertrain Control Module (PCM) cavity 36. The MAP sensor puts out a low voltage signal (0.5 to 1.8 volts) at idle when the manifold vacuum is high, and a higher voltage signal (3.9 to 4.8 volts) at deep throttle when the manifold vacuum is low. The MAP receives a 5-volt supply from PCM cavity 61; voltage may vary from 4.8 to 5.1 volts. The sensor ground is provided by PCM cavity 43.

NAME OF CODE: MAP Sensor Voltage Too High

When Monitored:
With engine RPM above 400 but less than 1500 and the Throttle Position (TP) sensor voltage less than 1.0 volt.

Set Condition:
The manifold Absolute Pressure (MAP) sensor signal voltage is greater than 4.6 volts at start or with the engine running for 1.76 seconds.

Possible Causes:
- Open 5-volt supply circuit
- Sensor open internally
- Sensor ground circuit
- Sensor signal circuit shorted to voltage
- Failed PCM
- Connector terminals
- Connector wires

NAME OF CODE: MAP Sensor Voltage Too Low

When Monitored:
With engine RPM above 400 but less than 1500 and the Throttle Position (TP) sensor voltage less than 1.0 volt.

Set Condition:
The Manifold Absolute Pressure (MAP) sensor signal voltage is below 1.2 volts at start, or below 0.2 volt for 1.76 seconds with engine running.

Possible Causes:
- Open 5-volt supply circuit
- Signal circuit shorted to ground
- Failed sensor
- Failed PCM
- Connector terminals
- Connector wires

NAME OF CODE: No 5 Volts to MAP Sensor

When Monitored:
With the ignition OFF.

Set Condition:
The MAP sensor signal voltage goes below 1.96 volts.

- The MAP receives a 5 volt supply from PCM cavity 61; voltage may vary from 4.8 to 5.1 volts.
- The sensor ground is provided by PCM cavity 43.

Possible Causes:
- Open 5 volt supply
- MAP sensor failure

NAME OF CODE: No Change in MAP From Start to Run

When Monitored:
With engine RPM above 400 but less than 1500 and the throttle body at closed throttle.

Set Condition:
Too small a difference is seen between barometric pressure at ignition on and manifold vacuum (engine running) for 1.76 seconds.

Possible Causes:
- Restricted or leaking vacuum/pressure to MAP sensor
- Ice in sensor or passage
- Failed sensor
- Failed PCM