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lexpert, Lexus Master tech
Category: Lexus
Satisfied Customers: 2100
Experience:  Master Certified with lexus, 8 years experience with Lexus
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I have 2002 ls430 Lexus cannot get 5 volts from ecm to knock

Customer Question

I have 2002 ls430 Lexus cannot get 5 volts from ecm to knock sensors
Submitted: 4 months ago.
Category: Lexus
Expert:  david craig replied 4 months ago.

Hi Im David, thanks for visiting the site, allow me a moment to look up some information for you. thank you.

Customer: replied 4 months ago.

hello what do you need to know

Expert:  david craig replied 4 months ago.

i dont need to know anything. im going to let you know what i thinks going on with your vehicle. thanks.

Customer: replied 4 months ago.

according to Aldata there is suppose to be 5 volts from ECM to sensors which comes from plug e6 pin 1&2 which ohm out and that is the wires but no volts

Expert:  david craig replied 4 months ago.

please give me a moment

Customer: replied 4 months ago.

no problem going to eat supper check you in a few

Expert:  david craig replied 4 months ago.

the knock sensor wires are located at D1 & D2 of that connector. you need to also check the shield ground for the sensor wiring to A15

Customer: replied 4 months ago.

where and how to check shield wiring and why am I not getting 5 volts from ECM pins 1 and 2 on plug e6 Also on the knock sensor print out I have it says that if you use flat type sensor the ECM supplies 5 volts. Dose anyone know how to repair this car .

Expert:  david craig replied 4 months ago.

shielded wires are part of the insulation that surrounds the conductor insulation. its usually braided. you would check it by probing the outer insulation jacket of the sensors connector with one lead and doing a continuity check of it to A15

Expert:  david craig replied 4 months ago.

are you sure you have the right prints?

Expert:  david craig replied 4 months ago.

if the ecm isnt supplying the volts then i suggest you check the grounds around the ecm mounting area and related ecm fuses

Customer: replied 4 months ago.

Is the braided wire around the wire that runs to the sensors and is a15 in which terminal my diagram has them # e2 thru e6

Expert:  david craig replied 4 months ago.

now this print doesnt show a shield ground. it shows the sensors having its own grounds

Expert:  david craig replied 4 months ago.

Using an ohmmeter, check that there is no continuity between the terminal and body of the sensors
If there is continuity, replace the sensor. is that what you did before you replace them?

Expert:  david craig replied 4 months ago.

there are so many fuses on this vehicle that control some output of the engine control. fuses that even labeled you would have no idea they had anything to do with the engine control

Customer: replied 4 months ago.

I was an idiot I took for granted that the codes were right and I pulled intake and bought two sensors from Lexus and replaced them and then found out that is not the problem. The last set of images you sent is what they show from Aldata for this car . I don't see any signs of braided wire even though the image shows some type o shielded wire. I did run continuity test on sensors and wiring the second time I took off intake before I bought new ECM . Now I have intake off for the third time and would like to repair it customer I s getting angry and I am tired

Expert:  david craig replied 4 months ago.

pick it back up tomorrow?

Customer: replied 4 months ago.

I have checked and ohm every fuse I could find still not getting 5 volts coming out of ECM

Customer: replied 4 months ago.

are you there on yet

Expert:  david craig replied 4 months ago.

im here

Expert:  david craig replied 4 months ago.

the only thing it can be is the ecm. replace it.

Customer: replied 4 months ago.

I did same results

Expert:  david craig replied 4 months ago.

replace it with a new one. and have it programmed to your vehicle... it cant be anything else if youve checked the wires from the ecm to the injectors. either that or you are missing a ground at the ecm

Customer: replied 4 months ago.

first of did you mean knock sensors I am not concerned with injectors and also were are the grounds for ECM located

Expert:  david craig replied 4 months ago.

sorry, yes the knock sensors

Expert:  david craig replied 4 months ago.

access the ecm and follow the harness you will find the grounds. should be in the immediate area

Expert:  david craig replied 4 months ago.

any update?

Expert:  david craig replied 4 months ago.

hello??

Customer: replied 4 months ago.

still not working going to try something else today will let you know

Expert:  david craig replied 4 months ago.

theres nothing left to try except some ecm related fuse.., if the wiring ohms out good to 15A, D1 and D2, and D1 and D2 arent reading to ground, theres nothing else.

Customer: replied 4 months ago.

can you send me a diagram of were 15A is in the ECM plugs and which plug you are using to make sure I am checking the correct wires

Expert:  david craig replied 4 months ago.

give me a while to dig that info up. thanks

Customer: replied 4 months ago.

ok

Expert:  david craig replied 4 months ago.

man this is getting more screwed up the longer i dig. now this is showing 32P and 35P

Expert:  david craig replied 4 months ago.

any update?

Customer: replied 4 months ago.

starting back to work on it this morning

Expert:  david craig replied 4 months ago.

ok. keep me updated and ill keep digging

Customer: replied 4 months ago.

you are saying to use pi 32 and pin 35 for the knock sensors my aldata my diagram shows e1 and e2 in pin plug e6

Customer: replied 4 months ago.

from your diagram I can see we are in the same pin plug you got make sure that pin numbers are correct because the wires that I ohm out are 1 white and 2 black and they ohm all the way back to knock sensor plug

Customer: replied 4 months ago.

in your early response you 15a d1 and d2 is 15a pin plug e6 that is middle plug of 3 plug combanation if so I have the right wires because 32 is brown and 35 is black if that is the case I am in the wrong the wires going to or coming from ECM have to be black and white according to wiring diagram

Expert:  david craig replied 4 months ago.

ok, let me get home and i will look in to this thoroughly

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