Absolute Pressure Sensor: Description and Operation

TMap Sensor (MINI COOPER S)
On the MINI COOPER S the pressure differential is measured across the supercharger to determine the manifold air density.

To measure this differential two sensors are fitted, one on either side of the supercharger. The TMAP is fitted on the manifold pressure side and has the same hardware specification as the MINI COOPER sensor but the maximum pressure range is 250 Kpa.

The MAP sensor is fitted upstream of the TMAP between the supercharger and the throttle body and measures the atmospheric pressure. This sensor is the same as the MINI COOPER TMAP but will not have the temperature sensor.

NOTE: Only the downstream TMAP has an intake air temperature sensor built into it.


The TMAP sensor is located in the intake manifold where it is exposed to higher than atmospheric pressures as produced by the supercharger. The MAP sensor is located between the supercharger and the EDR, a location not effected by additional pressures from the supercharger.

Intake Air Temperature Sensor
The air intake temperature sensor is built into the TMap sensor. Air temperature information is used in conjunction with intake manifold pressure information as supplied by the MAP enabling the EMS2000 to calculate the volume of air being consumed by the engine. The sensor is a NTC type, supplied 5 volts by the EMS2000.

High voltage readings at the EMS2000 indicate high sensor resistance, or low temperature. Low voltage readings indicate low sensor resistance or high temperature.


The first job of the MAP sensor is the measurement of the barometric pressure. Whenever the ignition key is in the "ON" position and the EMS2000 is supplied power from the Main Relay there is no piston action yet and the only reading sent to the computer is the barometric pressure signal (High Voltage).

Second, it measures the absolute pressure in the intake manifold. Absolute pressure is barometric pressure minus the vacuum created by the pistons. So, if the barometer is reading 1.5 Bar at sea level and the manifold vacuum (gauge) is 1.0 Bar at idle, the manifold absolute pressure would be 0.5 Bar.

The EMS2000 compares the voltage outputs from the MAP sensor (ahead of the supercharger) to the outputs received from the TMAP (subject to increased pressures from the supercharger) and calculates air volume drawn into the engine:

- Voltage Reading of 0.6-1.5 volts indicates high vacuum condition (Idle or no load)
- Voltage Reading of 4 volts indicates low vacuum condition (Full Throttle)

TMap and MAP Sensors Failure Symptoms
- Engine difficult to start, stalls at idle and misfires.

TMap and MAP Sensor Testing
- Ensure that voltage changes and does not remain constant at 0 or 5 volts.
- Install BOB on EMS2000 check voltage at appropriate pins.
- Check sensor for internal shorts.


Intake Air Temp Sensor Failure Symptoms
- Problems with cold starting, poor driveability and an increase in emissions.
- Possible lack of power, particularly noticeable in hot ambient temperatures.

With other possible failure modes the EMS2000 should ensure that the engine will limp home on a default value.

Intake Air Temp Sensor Testing
- Ensure that voltage changes and does not remain constant at 0 or 5 volts.
- Check Sensor Resistance.