Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Before continuing with this test, ensure that the following areas are in good condition:

• Vacuum hoses and connections.
• Wiring harness connectors.
• Fuel system.
• Added aftermarket equipment.
• Air intake filters and tubes.
• Base engine.

1. 1) Determine Intermittent Test Procedure
   
   Proceed to the appropriate intermittent test based on the following criteria:

   • Input Test
     
     This test applies only to input devices such as sensors and switches. It also applies to signals such as RPM and speed signals. This is the first testing procedure to use for checking input devices.
   • Output Test
     
     This test applies only to output devices such as fuel injectors, idle speed controllers, relays and solenoids. This is the first testing procedure to use for checking output devices.
   • Road Test
     
     This test applies to both input and output devices. This test usually is the second type of test to use (perform input or output test first).
   • Water Soak Test
     
     This test cannot be performed on all types of devices due to location of device (e.g. under instrument panel) or construction of device (damaged by water or not affected by water at all). This test usually is the last type of test to use in finding intermittent faults.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 10). No test procedures have been omitted.
2. 10) Input Test (KOEO)
   
   Turn ignition off. Connect NGS scan tool to OBD-II DLC. Select PIDs based on information from the test that sent you to this test. Turn ignition on. While observing PID value, wiggle and pull on component wiring and connector. See PIN VOLTAGE CHARTS article. Lightly tap on component. If PID value is within specification and does not abruptly change when wiggled, go to next step. If sudden change occurs in PID value or PID value drops out of range when wiggled, closely inspect each wire and connector for damage and repair as necessary. If fault cannot be located, replace suspect component. If replacement component does not repair fault, install original component and go to next step.
3. 11) Continue PID Monitoring
   
   Continue to monitor PIDs as in previous step. While observing PID value, wiggle and pull on wiring harness between suspect component and PCM. Lightly tap on component. If PID value(s) remain within specification, go to next step. If sudden change occurs in PID value or PID value drops out of sensor range, isolate fault and repair as necessary. If fault cannot be located, inspect PCM connector. If PCM connector is okay, replace PCM. If replacement PCM does not repair fault, install original PCM. Return to step 1) and choose another procedure.
4. 12) Input Test (KOER)
   
   Leave ignition on with PIDs accessed. Select PIDs from the area of suspected wiring or component fault. Start engine and allow to idle. While observing PID value, wiggle and pull on component wiring and connector. Lightly tap on component. If PID value(s) remain within specification, go to next step. See PIN VOLTAGE CHARTS article. If sudden change occurs in PID value or PID value drops out of sensor range, carefully inspect each wire and connector. If fault cannot be located, replace component. If replacement component does not repair fault, install original component and go to next step.
5. 13) KOER Wiring And Component Test
   
   Leave engine running at idle speed with PIDs accessed. While observing PID value, wiggle and pull on wiring harness between suspect component and PCM. Lightly tap on component. If PID value(s) remain within specification, fault cannot be identified with this procedure. Return to step  1) and choose another procedure. If sudden change occurs in PID value or PID value drops out of sensor range, isolate fault and repair as necessary. If fault cannot be located, replace PCM. If replacement PCM does not repair fault, install original PCM. Return to step 1)  and choose another procedure.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.
   NOTE: Some output devices require vehicle to be driven to be checked. In these cases, perform ROAD TEST.
6. 20) Intermittent KOEO Output Actuator Test
   
   Turn ignition off. Connect NGS scan tool to OBD-II DLC. Select PIDs based on information from the test that sent you to this test. Record trouble codes from PCM memory, if any are present. Turn ignition on. Enter OUTPUT TEST MODE on scan tool. Activate suspect component. While observing voltmeter reading and PID value, lightly tap on component. Compare readings to specification. See PIN VOLTAGE CHARTS article. If readings are correct and remain stable within one volt, go to next step. If readings are incorrect or unstable within one volt, replace component. If replacement component does not repair fault, install original component and go to next step.
7. 21) KOEO Wiring & Component Test
   
   Leave ignition on. Connect NGS scan tool. Continue to monitor PIDs. Turn outputs on. Wiggle and pull on wiring harness between suspect component and PCM. Lightly tap on component. Compare readings to specification. See PIN VOLTAGE CHARTS article. If readings are correct and remain stable within one volt, fault cannot be identified with this procedure. Return to step  1) and choose another procedure. If readings are incorrect or unstable within one volt, isolate fault and repair as necessary.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 30). No test procedures have been omitted.
8. 30) Water Soak Test
   
   Turn ignition off. Connect NGS scan tool to OBD-II DLC. Select PIDs based on information from test that sent you to this test. Start and idle engine. Spray water on suspect component, wiring and connectors. Watch for fault indicated by incorrect PID value, sudden change in PID value, or fluctuating engine speed. If no faults occur, go to next step. If fault occurs while spraying water on a component, replace part. Verify repair. If replacement part does not repair fault, reinstall original part. If fault occurs while spraying water on wiring, carefully inspect each wire and connector. Isolate and repair as necessary.
9. 31) KOER Water Soak Test
   
   With engine running, spray water on spark plugs, spark plug wires, ICM, and any related relays. Watch for fault indicated by incorrect PID value, sudden change in PID value or fluctuating engine speed. See PIN VOLTAGE CHARTS article. If no faults occur, fault cannot be identified with this procedure. Return to step 1) and choose another procedure. If fault occurs, isolate and repair as necessary.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 31) to step 40). No test procedures have been omitted.
10. 40) Road Test Procedure
    
    This procedure will monitor PIDs and components using a scan tool on a road test. An assistant is necessary for some portions of this test. This procedure is performed under 4 different conditions: KOEO, engine running at idle speed, 30 MPH and 55 MPH. Turn ignition off. Connect scan tool to DLC. Select suspect PIDs. Compare values to KOEO values given in PIN VOLTAGE CHARTS article. Watch for PID value(s) out of specification. If no faults are identified, go to next step. If input device fault occurs, return to step  10). If output fault occurs, return to step  20).
11. 41) Road Test Procedure (Hot Idle)
    
    Continue to monitor PID values as in previous step. Start and idle engine. With engine warmed to operating temperature, watch for fault indicated by incorrect PID value, sudden change in PID value, or fluctuating engine speed. Compare values to values given in PIN VOLTAGE CHARTS article. If values remain within specification, go to next step. If values do not remain within specification, return to step  10) for input system fault or step  20) for output system fault.
12. 42) Continue To Monitor PID Values
    
    Continue to monitor PID values as in previous step. Ensure all accessories are off. Using an assistant, test drive vehicle at 30 MPH. Watch for fault indicated by incorrect PID value, sudden change in PID value or fluctuating engine speed. Compare values to 30 MPH values given in PIN VOLTAGE CHARTS article. If values remain within specification, go to next step. If values do not remain within specification, go to step  10) for input system fault or step  20) for output system fault.
13. 43) Continue To Monitor PIDs
    
    Continue to monitor PID values as in previous step. Test drive vehicle at 55 MPH. Watch for fault indicated by incorrect PID value, sudden change in PID value or fluctuating engine speed. Compare values to 55 MPH values given in PIN VOLTAGE CHARTS article. If values remain within specification, fault cannot be identified with this procedure. Return to step  1) and choose another procedure. If values do not remain within specification, go to step  10) for input system fault or step  20) for output system fault.