Engine Controls - Tests W/o Codes: Other Volvo V90 I

Engine Does Not Crank

1. Check starter.
2. Check starter relay.
3. Check park/neutral or clutch start switch circuit.
4. Check theft deterrent ECU.

No Initial Combustion

1. Check fuel pump circuit.
2. Check RPM sensor circuit.
3. Check camshaft position sensor circuit.
4. Check power stage circuit.
5. Check MAF sensor circuit.
6. Check ECT sensor circuit.
7. Check fuel pressure.

Difficult To Start Normally

1. Check starter signal circuit.
2. Check Idle Air Control (IAC) valve circuit.
3. Check fuel pump control circuit.
4. Check ignition coil resistance.
5. Check distributor sensors (if applicable).
6. Check spark plugs.
7. Check engine compression.
8. Check fuel injector circuit.

Difficult To Start When Cold

1. Ensure battery is fully charged.
2. Ensure spark plugs fire strong Blue/White spark.
3. Check fuel pump fuse(s).
4. Check in-line fuse to control unit (if applicable).
5. Ensure ignition timing and fuel pressure are correct.
6. Check fuel injectors.
7. Ensure timing belt is not broken.
8. Check ground connections on intake manifold for control unit and power stage.
9. Ensure ignition coil resistance is correct.
10. Ensure rotor, distributor and plug wires are okay (if applicable).
11. Check ignition control unit.
12. Check coolant temperature sensor and connector.
13. Check throttle switch and connector.
14. Check fuel control unit.
15. Check engine speed sensor.
16. Ensure power stage receives signal from ignition control unit.
17. Check airflow sensor (if applicable).

Difficult To Start When Hot

1. Ensure fuel pressure is correct.
2. Check for gasoline in oil.
3. Ensure fuel injectors are not leaking.
4. Check ignition and sensor wires for proper connection.
5. Ensure spark plugs are not fouled.
6. Check ignition and coil circuit.
7. Check throttle switch and connector.
8. Check idle valve. Ensure airflow arrow points in correct direction.

Poor Idling

1. Check throttle switch and connection.
2. Check coolant temperature sensor and connection.
3. Check idle (air) valve.
4. Check air temperature sensor and mass airflow meter.
5. Check coolant temperature sensor.
6. Ensure spark plugs are not fouled.
7. Check ignition and sensor wires for proper connection.
8. Check idle valve. Ensure airflow arrow points in correct direction.
9. Check distributor (if applicable).
10. Check ignition and coil circuit.
11. Check intake system.
12. Check engine speed sensor.
13. Check throttle switch and connector.

Hesitation/Poor Acceleration

1. Defective airflow sensor.
2. Defective rotor/distributor cap (if applicable).
3. Damaged ignition wires.
4. Blocked air cleaner/air intake.
5. Uneven compression.
6. Low fuel pressure.
7. Blocked exhaust system.
8. Faulty sensor signals.
9. Faulty turbocharger (if applicable).
10. Wastegate valve open (if applicable).

Hesitation - Coasting

1. Check fuel injectors.
2. Check ignition and sensor wires for proper connection.
3. Check throttle switch and connector.
4. Check engine speed sensor.
5. Check for gasoline in oil.
6. Check idle valve. Ensure airflow arrow points in correct direction.

Muffler Explosion (Backfire)

1. Ensure ignition timing is correct.
2. Ensure timing belt has not jumped.
3. Check distributor (if applicable).
4. Check for gasoline in oil.
5. Ensure fuel injectors are not leaking.
6. Ensure spark plugs fire strong Blue/White spark.
7. Check ignition and coil circuit.
8. Check engine speed sensor.
9. Check throttle switch and connector.
10. Check exhaust system.

Engine Stall

1. Check cold start injector (if applicable).
2. Check coolant temperature sensor.
3. Check ignition and sensor wires for proper connection.
4. Check fuel injectors.
5. Check throttle switch and connector.
6. Check engine speed sensor.

Knocking

1. Check ignition and coil circuit.
2. Ensure spark plugs fire strong Blue/White spark.
3. Check knock sensor.
4. Check throttle switch and connector.
5. Check ignition and coil circuit.
6. Check engine speed sensor.

Engine Misfire

1. Check fuel injectors.
2. Check ignition and sensor wires for proper connection.
3. Check ignition and coil circuit.
4. Check for gasoline in oil.
5. Check intake and exhaust system.
6. Check throttle switch and connector.
7. Check for vacuum leaks.
8. Check engine speed sensor.

Insufficient Engine Power

1. Check fuel injectors.
2. Ensure fuel pressure is correct.
3. Check airflow sensor (if applicable).
4. Check for restricted exhaust.
5. Check coolant temperature sensor.
6. Check air temperature sensor.
7. Check engine speed sensor.
8. Check throttle switch and connector.
9. Check ignition and coil circuit.
10. Check engine speed sensor.
11. Check intake and exhaust system.

Poor Fuel Economy

1. Check for leaky fuel injectors.
2. Ensure spark plugs are not fouled.
3. Check for faulty oxygen sensor.
4. Check throttle switch and connector.
5. Check for poor wire connections and fouled spark plugs.
6. Check engine speed sensor.
7. Check for gasoline in oil.
8. Check for malfunctioning intake system.

Excessive HC & NOx

1. Check for gasoline in oil.
2. Check for leaky fuel injectors.
3. Check for faulty oxygen sensor.
4. Check ignition and sensor wires for proper connection.
5. Check engine speed sensor.
6. Check throttle switch and connector.
7. Check intake system.

Intermittent Simulation

Monitor circuit/component voltage or resistance while using the following procedures to simulate an intermittent fault. If engine is running, check for self-diagnostic codes. Use test results to identify a faulty component or circuit.

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component with water mist.
5. Remove vacuum from component.
6. Apply vacuum to component.