Circuit/System Testing

Always perform the Diagnostic System Check - Vehicle .

1. Start the engine.
2. Monitor the diagnostic trouble code (DTC) information with the scan tool.
3. If DTC P0641 or P0651 is also set, then correct DTC P0641 or P0651 first.
4. Inspect for the following conditions:
   • Disconnected, damaged or incorrectly routed vacuum hoses
   • MAP sensor disconnected from the vacuum source
   • Restrictions in the MAP sensor vacuum source
   • Intake manifold vacuum leaks
   • Check for a properly functioning oxygen sensor.
5. Turn OFF the ignition.
6. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
7. Connect a J 23738-A  Mityvac to the MAP sensor. See Special Tools .
8. Turn ON the ignition, with the engine OFF.
9. Observe the MAP sensor pressure with the scan tool.
10. Apply vacuum to the MAP sensor with the J 23738-A  in 1 inch Hg increments until 15 inches Hg is reached. See Special Tools . Each 1 inch Hg should decrease MAP sensor pressure by 3-4 kPa. Monitor the MAP sensor pressure to see if the decrease in pressure in consistent.
    • If decrease in pressure is not consistent, then test for intermittent and poor connections at the MAP sensor.
11. Apply vacuum with the J 23738-A  until 20 inches Hg is reached. See Special Tools . Observe the MAP sensor pressure for less than 34 kPa.
    • If more than 34 kPa, test for an intermittent and for a poor connection at the MAP sensor.
12. With the ignition ON and the engine OFF
13. Disconnect the manifold absolute pressure (MAP) sensor.
14. Measure for 4.8-5.2 volts from the 5-volt reference circuit of the MAP sensor to a good ground, with a DMM.
    • If more than the specified value, then test the circuit for a short to voltage or faulty control module.
    • If less than the specified value, then test the circuit for high resistance, an open or an intermittent and poor connection or at the control module or a faulty control module.
15. Disconnect the MAP sensor
16. Use a scan tool and observe the MAP sensor for less than 12 kPa.
    • If the MAP sensor is more than 12 kPa, then test the MAP sensor signal circuit for a short to voltage or a faulty control module.
17. Use a 3-amp fused jumper wire and connect it between the MAP sensor 5-volt reference circuit and the MAP sensor signal circuit.
18. Use a scan tool and observe the MAP sensor for more than 103 kPa.
    • If the MAP sensor is less than 103 kPa, then test the MAP sensor signal circuit for high resistance or a faulty control module.
19. With the 3-amp fused jumper wire still connected between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor, observe the MAP sensor parameter with the scan tool for 4.9V.
    • If more than 4.9V, then replace the MAP sensor.
    • If less than 4.9V, then test the MAP sensor signal circuit between the control module and the MAP sensor for a short to ground, an open or high resistance. Test for an intermittent and for a poor connection at the control module. If tests OK, then replace the control module.
20. Turn OFF the ignition and allow the control module to power down.
21. With a DMM, measure for less than 5 ohms of resistance between the low reference circuit of the MAP sensor and a good ground.
    • If the resistance is more than 5 ohms, then test the circuit for a high resistance or a faulty control module.
22. If the MAP sensor circuits test normal, then replace the MAP sensor.