With Speed Density Update

Flowchart Code 33:

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 33 will set when:

^ Engine running
^ Manifold pressure greater than 74 kPa (A/C "OFF") 83.4 kPa (A/C "ON").
^ Throttle angle less than 2% with vehicle in 1st gear or 6% in any other gear.
^ Conditions met for 5 seconds

Engine misfire or a low unstable idle may set Code 33.

2. With the MAP sensor disconnected, the ECM should see a low voltage if the ECM and wiring are OK.

DIAGNOSTIC AIDS
If idle is rough or unstable, refer to Diagnosis by Symptom for items which can cause an unstable idle. An open in CKT 455 or the connection will result in a Code33.

Ignition "ON" engine "OFF," voltages should be within the values shown in the table on the chart. Also, C-Charts Component Testing / Chart C-1D can be used to test the MAP sensor. Chart C-1D Manifold Absolute Pressure (MAP) Output Check