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HOMESERVICE MANUALSCHEVROLET1989PICKUP C2500, 2D PICKUP, 6.2 C, STANDARDREPAIR AND DIAGNOSISTRANSMISSIONAUTOMATIC TRANSDIAGNOSIS - TORQUE CONVERTER CLUTCHDIAGNOSTIC CHARTSMAP OUTPUT CHECK - COMPUTER COMMAND CONTROL
1989 Chevrolet Pickup C2500, 2D Pickup, 6.2 C, Standard

Map Output Check - Computer Command Control

1989 Chevrolet Pickup C2500, 2D Pickup, 6.2 C, StandardSECTION Map Output Check - Computer Command Control

The Manifold Absolute Pressure (MAP) sensor measures manifold pressure (vacuum) and sends that signal to the ECM. The MAP sensor is mainly used for fuel calculation, when ECM is running in the throttle body back-up mode. The MAP sensor is also used to determine barometric pressure and to help calculate fuel delivery.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This test checks MAP sensor output voltage to ECM. With engine off, this voltage represents barometric reading at ECM.
  2. Applying 10 in. Hg vacuum to MAP sensor should cause voltage to be about 1.2-2.3 volts less than voltage in step 1. Upon applying vacuum to sensor, the change in voltage should be immediate. A slow voltage change indicates a faulty sensor.
  3. Check vacuum hose to sensor for leaks or restrictions. Be sure no other vacuum devices are connected to MAP sensor vacuum hose.
Fig 1: MAP Output Check - Computer Command Control Flowchart
GB0044469
MAP ALTITUDE-TO-VOLTAGE VALUES

Altitude Feet (Meters) (1) Voltage Range VDC
Below 1,000 (Below 305) 3.8-5.5
1,000-2,000 (305-610) 3.6-5.3
2,000-3,000 (610-9140 3.5-5.1
3,000-4,000 (914-1219) 3.3-5.0
4,000-5,000 (1219-1524) 3.2-4.8
5,000-6,000 (1524-1829) 3.0-4.6
6,000-7,000 (1829-2133) 2.9-4.5
7,000-8,000 (2133-2438) 2.8-4.3
8,000-9,000 (2438-2743) 2.6-4.2
9,000-10,000 (2743-3048) 2.5-4.0
(1) Low Altitude = High Pressure = High Voltage
RENDER: 1.0x

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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