Fuel and Emissions Systems Symptom Troubleshooting Index
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.
4.
  • Low compression
  • No ignition spark
  • 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)
MIL comes on and stays on, or never comes on at all, no DTCs set
Engine will not start (MIL works OK, no DTCs set, immobilizer indicator stays on or flashes)
Check for symptoms for the immobilizer system.
Engine starts but stalls immediately (MIL works OK, no DTCs set, immobilizer indicator stays on or flashes)
Check for symptoms for the immobilizer system.
Engine is hard to start (MIL works OK, no DTCs set)
1.
2.
3.
  • Low compression
  • Intake air leaks
  • Contaminated fuel
  • Weak spark
Cold fast idle too low (MIL works OK, no DTCs set)
1.
2.
Cold fast idle too high (MIL works OK, no DTCs set)
1.
2.
3.
After warming up, idle speed is below specifications without load (MIL works OK, no DTCs set)
1.
2.
After warming up, idle speed is above specifications without load (MIL works OK, no DTCs set)
1.
2.
After warming up, idle speed drops when steering wheel is turning (MIL works OK, no DTCs set)
1.
2.
Power steering system
Idle speed fluctuates (MIL works OK, no DTCs set)
1.
2.
3.
4.
5.
6.
7.
Contaminated fuel
Misfire or rough running (MIL works OK, no DTCs set)
1.
2.
3.
4.
5.
  • Low compression
  • Valve clearance
  • Contaminated fuel
Fails emission test (MIL works OK, no DTCs set)
1.
2.
3.
4.
5.
6.
  • Contaminated fuel
  • Low compression
  • Slipped/broken timing belt
Low power (MIL works OK, no DTCs set)
1.
2.
3.
4.
5.
6.
  • Contaminated fuel
  • Low compression
  • Camshaft timing
  • Engine oil level
Engine stalls (MIL works OK, no DTCs set)
1.
2.
3.
4.
5.
6.
  • Intake air leaks
  • Faulty harness and sensor connections
HDS does not communicate with the ECM or the vehicle