Chart C-1D, Map Output Check
The Manifold Absolute Pressure (MAP) sensor measures intake manifold vacuum and sends an electrical signal to ECM. The MAP sensor is mainly used to to calculate engine load, which allows ECM to control fuel delivery and spark timing.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Checks MAP sensor output voltage to ECM. This voltage, with engine off, represents a barometer (BARO) reading to ECM. Comparing BARO reading with a known good vehicle, with same sensor, is a good way to check accuracy of a suspect sensor. Reading should be the same +/- .4 volt.
- Applying 10 in. Hg to MAP sensor should cause voltage to be 1.2 volts less than in step 1). When applying vacuum to sensor, voltage change should be immediate. A slow changing sensor indicates a defective sensor.
- Check vacuum hose to sensor for leaks or restrictions. Ensure no other vacuum hoses are connected to MAP sensor vacuum hose. The engine must be running in this step or the "Scan" tester will not detect a change in voltage. It is normal for the SES light to come on and for a Code 33 to set in memory. Clear code when test is complete.