Engine Controls - Tests W/o Codes - 2.5L V6: Other Saab 900 II

DIFFICULT TO START

1. Check battery and cables, charging system, and fusible links.
2. Check ignition switch.
3. Check clutch start switch (M/T) or neutral start switch (A/T)
4. Check starter and wiring connections.

ROUGH OR UNSTABLE IDLE

1. Check temperature sensor operation.
2. Check Manifold Absolute Pressure (MAP) sensor (if equipped).
3. Check for proper CO setting (if adjustable) on mass airflow sensor. Inspect for broken mass airflow sensor filament (if equipped). Check mass airflow sensor continuity.
4. Inspect induction system. Inspect for vacuum leaks downstream of throttle valve. Inspect duct between mass airflow sensor and throttle body (if equipped).
5. Check idle speed and EGR valve (if equipped).
6. Check injector operation and opening duration. Inspect injectors for leaks.
7. Ensure fuel pump is okay. Check fuel pressure and pressure regulator. Inspect for leaks in fuel lines or restrictions in return line.
8. Ensure electrical harness, connectors, and wires are not broken or loose. Check all input signals to ECM.
9. Check EGR valve (if equipped) for proper operation.
10. Check oxygen sensor.

ENGINE HESITATES OR MISSES

1. Check Manifold Absolute Pressure (MAP) sensor (if equipped).
2. Ensure wiring harness, connections, and wires are not broken or loose. Check ECM connector pins and all ECM input signals.
3. Check charging system for low output or poor ground connection. Check all electrical connections for tightness.
4. Check fuel injector operation and opening duration. Inspect injectors for leaks.
5. Check turbo (if equipped) and Automatic Performance Control (APC) systems for proper operation.
6. Verify mass airflow sensor filament is not broken and burn -off function is working (if equipped).
7. Inspect induction system. Inspect for vacuum leaks downstream of throttle valve. Inspect duct between mass airflow sensor (if equipped) and throttle body.
8. Verify fuel pump is okay. Check fuel pressure and pressure regulator. Inspect for leaks in fuel lines or restrictions in return line.
9. Check temperature sensor(s).
10. Check Throttle Position (TP) sensor.
11. Check trigger signals to Ignition Discharge Module (IDM).

POOR FUEL MILEAGE

1. Ensure fuel pump is okay. Check fuel pressure and pressure regulator. Inspect for fuel leaks or restrictions in return line.
2. Check injector operation by individually unplugging connectors. Engine RPM should drop noticeably. Check opening duration. Inspect injectors for leaks.
3. Check coolant temperature sensor.
4. Check Manifold Absolute Pressure (MAP) sensor (if equipped).
5. Check intake air temperature sensor (if equipped).
6. Check Throttle Position (TP) sensor.
7. Verify mass airflow sensor filament is not broken and burn -off function is okay (if equipped).
8. Ensure electrical harness, connectors, and wires are not broken or loose. Check all input signals to ECM.

ENGINE WILL NOT START

1. Ensure electrical harness, connectors, and wires are not broken or loose. Check component grounding points. Ensure battery voltage is at least 11.5 volts. Check system relay and fuel pump relay. On turbo models, check pressure switch. Check all ECM input signals.
2. Using a spark tester, verify spark exists at plugs.
3. Ensure fuel pump operates. Check fuel pressure and pressure regulator. Inspect for plugged fuel filter or restrictions in return line.
4. Check injector operation.
5. Inspect induction system. Inspect for leaks downstream of throttle valve. Inspect duct between mass airflow sensor (if equipped) and throttle body.
6. Check coolant temperature sensor operation.
7. Check Idle Air Control (IAC) valve.

ENGINE STARTS BUT STOPS

1. Ensure electrical harness, connectors, and wires are not broken or loose. Ensure battery voltage is at least 11.5 volts. Check system relay and fuel pump relay. On turbo models, check pressure switch. Check all ECM input signals.
2. Check Manifold Absolute Pressure (MAP) sensor (if equipped).
3. Check coolant temperature sensor operation.
4. Inspect induction system. Inspect for leaks downstream of throttle valve. Inspect duct between mass airflow sensor (if equipped) and throttle body.
5. Ensure CO is not too high or too low.
6. Check Throttle Position (TP) sensor.
7. Check Idle Air Control (IAC) valve.

POOR RESPONSE ON ACCELERATION

1. Check mass airflow sensor (if equipped) for proper CO setting (if adjustable) and for broken filament. Check mass airflow sensor resistance.
2. Inspect induction system. Inspect for leaks downstream of throttle valve. Inspect duct between mass airflow sensor (if equipped) and throttle body.
3. Check idle speed.
4. Check injector operation and opening duration. Inspect injectors for leaks.
5. Verify fuel pump is okay. Check fuel pressure and pressure regulator. Inspect fuel line for leaks or restrictions. Check fuel filter.
6. Ensure electrical harness, connectors, and wires are not broken or loose. Check all input signals to ECM.
7. Check temperature sensor(s).
8. Check oxygen sensor.

LACK OF POWER

1. Inspect induction system. Inspect for air leaks downstream of throttle valve. Inspect duct between mass airflow sensor (if equipped) and throttle body.
2. Inspect throttle valve for binding and proper adjustment. Ensure throttle valve opens completely.
3. Verify fuel pump is okay. Check fuel pressure and pressure regulator. Inspect for leaks or restrictions in fuel line. Check fuel filter.
4. Check injector operation by individually unplugging connectors. Engine RPM should drop noticeably. Check opening duration. Inspect injectors for leaks.
5. Check Manifold Absolute Pressure (MAP) sensor (if equipped).
6. Verify mass airflow sensor filament is not broken and burn -off function is working (if equipped).
7. Check turbo and Automatic Performance Control (APC) systems for proper operation.
8. Check coolant temperature sensor operation.
9. Check intake air temperature sensor operation.
10. Ensure electrical harness, connectors, and wires are not broken or loose. Check all input signals to ECM.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component with water mist.
5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.