Circuit/System Testing

Always perform the Diagnostic System Check - Vehicle.

1. If DTCs P0107, P0108, P0641, P0651 are also set, diagnose them first.
2. Turn OFF the ignition.
3. Remove the BARO sensor and the MAP sensor.
4. Inspect each sensor for a plugged port.
IMPORTANT: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure, and/or very low or very high temperature, may cause a reading to be slightly out of range.
5. Turn ON the ignition, with the engine OFF.
6. Observe the BARO parameter with a scan tool. Refer to Altitude vs Barometric Pressure . The BARO parameter should be within the range specified for your altitude.
   • If the BARO sensor does not indicate the correct barometric pressure, then test for an intermittent and for a poor connection at the BARO sensor.
7. Observe the BARO parameter and the MAP Sensor parameter with a scan tool. Compare the values. The difference between the values should be less than 3 kPa.
   • If more than 3 kPa, then test for an intermittent and for a poor connection at the MAP sensor.
8. Turn OFF the ignition.
9. Connect a J 23738-A  to the BARO sensor port.
10. Turn ON the ignition, with the engine OFF
11. Monitor the BARO parameter with the scan tool.
12. Apply vacuum with the J 23738-A  SLOWLY, 1 inch Hg at a time. Each inch of vacuum should result in a 3-4 kPa drop in the BARO sensor pressure.
13. Increase the vacuum to 20 inches Hg.
    • If does not increase smoothly, then test for an intermittent and for a poor connection at the BARO sensor.
14. Disconnect the J 23738-A  from the BARO sensor port. Observe the BARO sensor to see if it returns to the normal range. Refer to Altitude vs Barometric Pressure .
    • If the BARO sensor does not return to the normal range, then replace the BARO sensor.
15. Turn OFF the ignition.
16. Remove the MAP sensor from the vacuum source, leaving the harness connected.
17. Connect a J 23738-A  to the MAP sensor port.
18. Turn ON the ignition, with the engine OFF.
19. Monitor the MAP sensor parameter with the scan tool.
20. Apply vacuum with the J 23738-A  SLOWLY, 1 inch Hg at a time. Each inch of vacuum should result in a 3-4 kPa drop in the MAP sensor pressure.
21. Increase the vacuum to 20 inches Hg.
    • If MAP sensor parameter does not decrease smoothly during test, then test for an intermittent and for a poor connection at the MAP sensor.
22. Disconnect the J 23738-A  from the MAP sensor port. Observe the MAP sensor to see if it returns to the normal range.
    • If does not return to the normal range, then replace the MAP sensor.
23. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the BARO sensor and the signal circuit of the BARO sensor and observe the scan tool parameter for 198 kPa.
    • If more than 198 kPa, then replace the BARO sensor.
    • If less than 198 kPa, then test the signal circuit of he BARO sensor for high resistance.
24. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor at the harness connector and observe the scan tool parameter for 4.75 volts.
    • If more than 4.75 volts, then replace the MAP sensor.
    • If less than 4.75 volts, then test the signal circuit of he MAP sensor for high resistance.