Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
- Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM.
- Start the engine. Observe the MAF SENSOR parameter with a scan tool. Is the MAF SENSOR parameter less than 1135 Hz? If yes, go to step 4. If no, go to next step.
- Observe the Freeze Frame/Failure Records for this DTC. Turn off the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
- Observe the MAF SENSOR parameter with a scan tool. Move the harness and the connector of the Mass Airflow (MAF) sensor. Does the movement of the harness or the connector affect the MAF SENSOR parameter? If yes, go to step 18. If no, go to next step.
- Turn OFF the ignition. Inspect for the following conditions:
- A restricted or collapsed air intake duct.
- A misaligned air intake duct.
- A dirty or deteriorating air filter element.
- Any objects blocking the air inlet screen of the MAF sensor.
- Any vacuum leak down stream of the MAF sensor.
- Any contamination or debris on the sensing elements of the MAF sensor.
Did you find and correct the condition? If yes, go to step 25. If no, go to next step.
- Inspect the fuse in the MAF sensor ignition 1 voltage circuit. Is the fuse open? If yes, go to step 12. If no, go to next step.
- Turn ignition on, with engine off. Disconnect the MAF sensor. Connect a test light between the MAF sensor ignition 1 voltage circuit and a good ground. Connect a DVOM between the probe of the test light and a good ground. Is voltage less than battery voltage? If yes go to step 19. If no, go to next step.
- Turn off the ignition for 60 seconds to allow the control modules to power down. Measure the resistance between the MAF sensor ground circuit and a good ground. Is the resistance less than 5 ohms? If yes, go to next step. If no, go to step 20.
- Turn ignition on, with engine off. Measure the voltage between the MAF sensor signal circuit and a good ground. Is the voltage 4.0-4.5 volts? If yes, go to step 11. If no, go to next step.
- Is the voltage less than 4.5 volts? If yes, go to step 13. If no, go to step 14.
- Turn ignition off. Disconnect the PCM. Test the signal circuit between the PCM and the MAF sensor for a high resistance. Did you find and correct the condition? If yes, go to step 25. If no, go to step 16.
- Test the ignition 1 voltage circuit for a short to ground. Did you find and correct the condition? If yes, go to step 25.
- Turn ignition off. Disconnect the PCM. Test the signal circuit between the PCM and the MAF sensor for a high resistance, an open circuit or a short to ground. Did you find and correct the condition? If yes, go to step 25. If no, go to step 15.
- Turn ignition off. Disconnect the PCM. Turn ignition on, with engine off. Measure the voltage between the MAF sensor signal circuit and a good ground. Is the voltage more than zero volts? If yes, go to step 21. If no, go to next step.
- Measure the resistance between the MAF sensor signal circuit and all other circuits at both PCM connectors. Is the resistance less than infinity? If yes, go to step 22. If no, go to step 17.
- Test for an intermittent and/or poor connections at the MAF sensor. Did you find and correct the condition? If yes, go to step 25. If no, go to step 23.
- Test for an intermittent and/or poor connections at the PCM. Did you find and correct the condition? If yes, go to step 25. If no, go to step 24.
- Repair the wiring or the connector as needed. Did you complete the repair? If yes, go to step 25.
- Repair the high resistance or an open in the MAF sensor ignition 1 voltage circuit. Did you complete the repair? If yes, go to step 25.
- Repair the high resistance or an open in the MAF sensor ground circuit. Did you complete the repair? If yes, go to step 25.
- Repair the short to voltage in the MAF sensor signal circuit. Did you complete the repair? If yes, go to step 25.
- Repair the circuits that are shorted together. Did you complete the repair? If yes, go to step 25.
- Replace MAF sensor. See MASS AIRFLOW/INTAKE AIR TEMPERATURE SENSOR under SENSORS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to step 25.
- Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to next step.
- Clear the DTCs with a scan tool. Turn off the ignition for 30 seconds. Start the engine and operate vehicle within the Conditions For Running DTC. You may also operate vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to step 2. If no, go to next step.
- Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
NOTE:
All electrical components and accessories must be turned off.
NOTE:
An abnormal resistance on the signal circuit will disable the frequency signal before the voltage drops out of the correct parameter.
NOTE:
The ignition 1 voltage circuit of the MAF sensor is spliced to other components of the vehicle.
NOTE:
Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit.