2005 Lexus LS 430FACTORY OEM SERVICE PROCEDURE

Problem Symptoms Table

PROBLEM SYMPTOMS TABLE - ENGINE CONTROL SYSTEM

Symptom Suspected Area
Engine does not crank (does not start)
  • 44. Starter
  • 45. STARTER relay
  • 46. Ignition Switch
No initial combustion (does not start)
  1. ECM power source circuit
  2. Fuel pump control circuit
  3. ECM
Engine cranks normally (difficult to start)
  1. Fuel pump control circuit
  2. Compression
Cold engine (difficult to start)
  1. Starter signal circuit
  2. Fuel pump control circuit
  3. Spark plug
  4. Ignition system
  5. Injector
Hot engine (difficult to start)
  1. Starter signal circuit
  2. Fuel pump control circuit
  3. Spark plug
  4. Ignition system
  5. Injector
High engine idle speed
  1. A/C signal circuit (compressor circuit)
  2. ECM power source circuit
  3. Electronic throttle control system
  4. Air induction system
  5. PCV hose
Low engine idle speed
  1. A/C signal circuit (compressor circuit)
  2. Fuel pump control circuit
  3. Electronic throttle control system
  4. Air induction system
  5. PCV hose
Rough idling
  1. Compression
  2. Fuel pump control circuit
  3. Electronic throttle control system
  4. Air induction system
  5. PCV hose
Hunting (when idling)
  1. ECM power source circuit
  2. Fuel pump control circuit
  3. Spark plug
  4. Ignition system
  5. Injector
  6. Electronic throttle control system
  7. Air induction system
  8. PCV hose
Hesitation/Poor acceleration (poor driveability)
  1. Fuel pump control circuit
  2. A/T faulty
  3. Spark plug
  4. Ignition system
  5. Injector
Surging (poor driveability)
  1. Fuel pump control circuit
  2. Spark plug
  3. Ignition system
  4. Injector
Engine stalls soon after starting
  1. Fuel pump control circuit
  2. Spark plug
  3. Ignition system
  4. Injector
Engine stalls during A/C operation
  1. A/C signal circuit (Compressor circuit)
  2. ECM
Unable/difficult to refuel Refueling valve (canister)
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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