H28 - Check MAP Sensor For Vacuum Leak

NOTE: Due to the Manifold Absolute Pressure (MAP) sensor's large influence on fuel control, there is a possibility that MAP could be at fault without a Diagnostic Trouble Code (DTC) 126. The next two test steps will verify proper vacuum to the MAP sensor and its ability to hold vacuum.

- Key "OFF".

- Disconnect vacuum line from MAP sensor.

- Inspect hose for blockage (kinks or gel build up), damage from wear or aging. Service as necessary.

- Plug vacuum hose at the MAP side.

- Connect a vacuum pump to the MAP sensor and apply 60 kPa (18 in Hg) vacuum to MAP sensor.

- Does MAP sensor hold vacuum?

Yes -- Release vacuum. Go to H29. H29 - Check For Loss of Vacuum to MAP Sensor

No -- Replace MAP sensor. Remove vacuum pump. Reconnect HO2S. Drive vehicle 5 miles/55 mph. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)