With Speed Density Update

Chart - Code 33 Manifold Absolute Pressure (MAP)signal voltage low, high vacuum:

Wiring Diagram for Manifold Absolute Pressure (MAP):

CIRCUIT DESCRIPTION:
The manifold absolute pressure sensor (MAP) responds to changes in vacuum (manifold pressure). The ECM receives this information as a voltage that varies from about 1-1.5 volts at idle (high vacuum) to 4-4.5 volts at wide open throttle (low vacuum).

TEST DESCRIPTION:
Numbers below refer to circled numbers on the diagnostic chart.
1. Code 33 will set if:
- Engine is running.
- Manifold pressure is more than 74.3 kPa with A/C off or 83.4 kPa with A/C on.
- Throttle angle is less than 2% with vehicle in 1st gear or 6% in in any other gear.
- Conditions are met for 5 seconds.
Engine misfire or a low unstable idle may set a code 63.

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

DIAGNOSTIC AIDS
- If idle is unstable see DIAGNOSIS BY SYMPTOM. Testing and Inspection
- An open in CKT 455 or connections will set a code 33.
- Voltage should be within specs in chart.