With Speed Density Update

Flowchart Code 34:

Wiring Diagram:

CIRCUIT DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum), The Electronic Control Module (ECM) receives this information as a signal voltage that will vary from about 1 to 1.5 volts at idle (high vacuum) to 4 to 4.5 volts at wide open throttle (low vacuum).


TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. Code 34 will set if:

^ Engine rpm less than 700
^ Manifold pressure reading less than 13 kPa
^ Conditions met for 1 second

OR

^ Engine rpm greater than 700
^ Throttle angle over 20%
^ Manifold pressure less than 13 kPa
^ Conditions met for 1 second

2. This test to see if the sensor is at fault for the low voltage or if there is an ECM or wiring problem.

3. This simulates a high signal voltage to check for an open in Circuit (CKT) 432. If the test light is bright during this test, CKT 432 is probably shorted to ground. If "Scan" reads over 4 volts at this test, CKT 474 can be checked by measuring the voltage at terminal "C" (should be 5 volts).


DIAGNOSTIC AIDS
An intermittent open in CKTs 432 or 474 will result in a Code 34.
Ignition "ON" engine "OFF," voltages should be within the values shown in the table on the chart. Also C-Charts Component Tests / Chart C-1D can be used to test MAP sensor. Chart C-1D Manifold Absolute Pressure (MAP) Output Check
Refer to Diagnosis by Symptom. Testing and Inspection