Manifold Absolute Pressure (Map) Output Check - Isuzu 1999 RODEO Workshop Manual

6E1–100 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

MANIFOLD ABSOLUTE PRESSURE (MAP) OUTPUT CHECK

Circuit Description
The manifold absolute pressure (MAP) sensor measures
the changes in the intake MAP which result from engine
load (intake manifold vacuum) and engine speed
changes; and converts these into a voltage output. The
powertrain control module (PCM) sends a 5–volt
reference voltage to the MAP sensor. As the MAP
changes, the output voltage of the sensor also changes.
By monitoring the sensor output voltage, the PCM knows
the MAP. A lower pressure (low voltage) output voltage
will be about 1–2 volts at idle. Higher pressure (high
voltage) output voltage will be about 4–4.8 volts at wide
open throttle. The MAP sensor is also used, under certain
conditions, to measure barometric pressure, allowing the
PCM to make adjustments for different altitudes. The
PCM uses the MAP sensor to diagnose proper operation
of the EGR system, in addition to other functions.
Test Description
IMPORTANT: Be sure to use the same diagnostic test
equipment for all measurements.
The number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. When you compare the Tech 2 readings to a known
good vehicle, it is important to compare vehicles
that use MAP sensors that have the same part
number.
2. Applying 34 kPa (10 Hg) vacuum to the MAP sensor
should cause the voltage to be 1.5–2.1 volts less
than the voltage at step 1. Upon applying vacuum to
the sensor, the change in voltage should be
instantaneous. A slow voltage change indicates a
faulty sensor.
3. Check the vacuum hose to the sensor for leaking or
restriction. Be sure that no other vacuum devices
are connected to the MAP hose.
IMPORTANT: Make sure the electrical connector
remains securely fastened.
4. Disconnect the sensor from the bracket. Twist the
sensor with your hand to check for an intermittent
connection. Output changes greater than 0.10 volt
indicate a bad sensor.
D06RX042