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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Lexus
Satisfied Customers: 1522
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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I HAVE A 96 LS400 WONT RUN HAS PLENTY OF SPARK AND ONLY

Customer Question

HI I HAVE A 96 LS400 WONT RUN HAS PLENTY OF SPARK AND ONLY INJECTION ON STARTUP RUNS FOR A COUPLE SECONDS AND DIES IVE PLUGGED A NOIDE LIGHT IN AN INJECTOR AND A SPARK TESTER INLINE WITH A COIL WIRE . WHEN IT DIES AND I CONTINUE CRANKING SPARK IS PLENTIFUL BUT NO INJECTOR PULSE. ANY IDEAS WHERE TO START OR EVEN A PINPOINT TEST I COULD FOLLOW FOR THIS.
Submitted: 1 year ago.
Category: Lexus
Expert:  Juan Crespo replied 1 year ago.

Hi there. Just logged in and saw your question.

There are two ways to diagnose this issue:

1- The easy way - Plug in a scan tool that allows us to "see" the same data the ECU is "seeing" so we can determine the root cause of the problem

2- The hard way - Use a multimeter to check pertinent sensor and actuator signals one by one until we find the problem

I can certainly guide you through either way. How would you like to proceed?

Customer: replied 1 year ago.
Is there not a pinpoint test for this concern that is not really an answer to my question. I've been a tech for 24 years and usually with the proper flow chart I can figure it out I don't have a pinpoint test or flow chart for no start with spark and no injection pulse . But yes I do have a scan tool.
Expert:  Juan Crespo replied 1 year ago.

Lexus does not provide a particular pinpoint test or flow chart we could follow for this concern. However, knowing how the system works should help us formulate our own diagnostic procedure.

First step is to plug in the scan tool and check for any current or pending codes; then look at engine data to see if we can catch any abnormal PIDs - pay close attention to system voltage as well as IAC and TPS values.

If everything is normal, then we need a voltmeter to find the reason why the injectors stop working; is it because they're loosing power from the 10A ignition fuse or ground from the ECU. If they're loosing power, we might be looking at a poor connection somewhere in the injector power circuit. If they're loosing ground, then we need to go back to the scan tool to see what is causing the ECU to stop actuating the injectors.

Please run the tests above and let me know what you find.

Best Regards.

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