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.  
Hard starting
(MIL works OK, no DTCs set) 
1.
2.
3. 
Test the battery.
Bleed the fuel system.
Test the fuel filter water level switch. 
  • Low compression
  • Intake air leaks
  • Contaminated fuel
 
Cold fast idle too low
(MIL works OK, no DTCs set) 
1.
2.
3. 
Check the idle speed.
Bleed the fuel system.
Test the fuel filter water level switch. 
 
Cold fast idle too high
(MIL works OK, no DTCs set) 
1.
2.
3. 
Check the idle speed.
Inspect/adjust the throttle cable.
Test the fuel filter water level switch. 
 
Idle speed fluctuates
(MIL works OK, no DTCs set) 
1.
2.
3.
4. 
Check the idle speed.
Inspect/adjust the throttle cable.
Bleed the fuel system.
Test the fuel filter water level switch. 
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) 
1.
2. 
Bleed the fuel system.
Test the fuel filter water level switch. 
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