Fuel and Emissions Systems Symptom Troubleshooting

When the vehicle has one of these symptoms, check for a diagnostic trouble code (DTC) with the HDS. If there is no DTC, do the diagnostic procedure for the symptom, in the sequence listed, until you find the cause.

Symptom | Diagnostic procedure | Also check for
--- | --- | ---
Engine will not start (MIL works OK, no DTCs set) | 1. 2. 3. | Test the battery. Test the starter. Bleed the fuel system. | Low compression Intake air leaks Locked up engine Broken cam chain Contaminated fuel
Engine will not start (MIL comes on and stays on, or never comes on at all, no DTCs set) | Troubleshoot the MIL circuit. |
Engine will not start (immobilizer indicator stays on or flashes) | Troubleshoot the immobilizer system. |
Engine is hard to start (MIL works OK, no DTCs set) | 1. 2. | Test the battery. Bleed the fuel system. | Low compression Intake air leaks Contaminated fuel
Cold fast idle too low (MIL works OK, no DTCs set) | 1. 2. | Check the idle speed. Bleed the fuel system. |
Cold fast idle too high (MIL works OK, no DTCs set) | 1. 2. | Check the idle speed. Inspect/adjust the throttle cable. |
Idle speed fluctuates (MIL works OK, no DTCs set) | 1. 2. 3. | Check the idle speed. Inspect/adjust the throttle cable. Bleed the fuel system. | Intake vacuum leaks
After warming up, idle speed is above specifications without load (MIL works OK, no DTCs set) | Inspect/adjust the throttle cable. |
Idle speed fluctuates (MIL works OK, no DTCs set) | Bleed the fuel system. | Contaminated fuel
Fails emission test (MIL works OK, no DTCs set) | Inspect the catalytic converter. | Contaminated fuel Low compression Slipped/broken timing belt
Low power (MIL works OK, no DTCs set) | 1. 2. 3. | Check the air cleaner element. Inspect/adjust the throttle cable. Inspect the catalytic converter. | Contaminated fuel Low compression Camshaft timing Engine oil level
Engine stalls (MIL works OK, no DTCs set) | 1. 2. | Bleed the fuel system. Check the idle speed. | Intake air leaks Faulty harness and sensor connections