Lexus 300 engine fails to start

Assembly 3VZ-FE engine Lexus 300 sedan. Users report: car engine suddenly does not start, but the starter is operating normally.
Failure Analysis: For the electronically controlled engine , if the engine can drive the rotation starter , but can not start trouble , you should have digiprog iii v4.88 the following seven kinds of possibilities:
( 1 ) car alarm system is triggered , causing the engine can not be started . For this possibility , through theft indicator on the instrument can determine immediately whether the cause is due to the anti-theft system is triggered .
( 2 ) Due to the starter battery power loss or failure in itself , cause the engine cranking speed is low and can not start. For this possibility , by starting the engine while observing the functioning of the starter can be determined .
( 3 ) Fuel pressure too low or unable to establish fuel pressure. For this possibility , as long as you can check the fuel supply system .
( 4 ) oil ( fuel injection control means ) no fire can not start . Mainly the ignition system failure.
( 5 ) can not start a fire without oil . Mainly the fuel injection control system failure.
( 6 ) no oil no fire can not start. The main sub-cylinder should be checked whether the signal is lost, the engine control unit power supply and ground connection is good.
( 7 ) oil can not start a fire . The main should check valve timing and cylinder pressure.
Troubleshooting : Exclude car starter vain failure , a condition which is mainly to find the destruction of the engine starting, the spirit from outside to inside , from simple to complex procedures on the car one by one investigation .
Unplug the main high-voltage power lines arcing inspection , the starter starter, no high-voltage spark generated ; then injector test light to check the work , only work when just start injector 1 to 2 times. The initial recognition of the fault in the ignition system . Ignition system failure will cause ECU to stop fuel injection. Because each engine ignition , ignition feedback to ECU 1个ignition confirmation signal "IGF" as a self- diagnostic system monitoring signal , if ECU Chip Tunning 4 times in a row did not receive "IGF" signal that stops fuel injection.
Check the ignition, the ignition coil plugs are connected properly ; powered check the ignition coil in the ignition switch is turned to the battery voltage , it is normal.
The test lamp connected between the positive and negative ignition coil , the starter drive the engine is running , the test light does not respond , indicating that control the ignition coil ignition not working .
Vehicle engine ignition system circuit shown in Figure 1 .

 As can be seen from Figure 1, the igniter plug has five terminals in total : "B" of power from the ignition switch , "C" for the control of the primary side of the ignition coil , "T" for the engine control computer the ignition signal input , "F" ignition feedback signal , "XT" signal is output to the engine speed , the engine output to the dashboard tachometer .
Check ignition supply voltage , ignition "B" terminal when the ignition switch is turned to the battery voltage .
Then check the engine computer to the ignition of the ignition control signal. A test light emitting diodes connected between the igniter "T" terminal and the ground , the light emitting diode flashes when operating the starter , ignition control signal indicates normal .
Then test light -emitting diode connected between the ignition "F" terminal and the ground , when the starter did not change the brightness of the light emitting diode operation , indicating that IGF ignition feedback signal a problem .
Igniter power supply is normal , the ignition control signal is received the engine computer , but neither the control ignition high voltage ignition coil , ignition did not occur the feedback signal to check this , seems to confirm the failure of the igniter .
Schematic it again and found the ignition circuit is no separate grounding wire , ignition through their metal grounding, then ignition grounding is good too ?
Turn the ignition switch , ignition voltage multimeter to measure the metal shell and the body between the metal casing found ignition voltage is present and the body GDS VCI Diagnostic Tool for KIA Hyundai grounding of nearly 10v . Check the ignition of the fixed installation , and there found loose bolts corrosion phenomenon .
Check this , the real cause of the failure is determined to be caused by bad ignition housing Ground ignition does not work. The igniter fixing bolts corroded surface clean , smooth re-start the car engine , engine troubleshooting.
Maintenance Summary: When troubleshooting the vehicle malfunction , first determine what kind of causes the engine can not start , and then find relevant technical information, detailed investigation. The car fault diagnosis in the process, when it is judged ignition failure , do not blindly replaced with new parts, but further analysis and diagnosis , to find the specific cause of the failure of the ignition , so as to be targeted.