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Pete, Technician
Category: Lexus
Satisfied Customers: 27878
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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Skyvisions. I have a 2005 Lexus LS430 and I'm having an

Customer Question

Hi Skyvisions. I have a 2005 Lexus LS430 and I'm having an issue with the oxygen sensor. I have the car at a local mechanic who I really trust and here's what's happened so far. Please let me know if you have any advice.
- I started noticing the check engine light/VSC off/red exclamation mark dash lights coming on a few months ago. It was intermittent and I could not see a pattern. These lights might come on for a day or 2 weeks, then go off for a day or 2 weeks.
- I took the car to a local Firestone repair shop very close to my house (this is not the place where the car is now, just where I go if I need a quick look/diagnostic).
- They did a diagnostic and said that my spark plugs were fowled out and that the dash lights were probably coming on because of that.
- I took the car to my mechanic (where the car is now) and had him change the plugs and do a injector & throttle body cleaning.
- When I picked up the car, the dash lights were off.
- Within a week or two the lights came back on. I brought it back to my mechanic.
- He said that they computer reading was saying that the oxygen sensor was bad. We replaced it. When I picked up the car, the dash lights were off.
- 2 days later the dash lights came back on. I brought the car back to the mechanic. He started looking at the wiring and noticed that the wiring had been electrical taped, so someone must have worked on these wires before. He speculated that these wires run so close to the exhaust that they probably melted and someone had to fix it previously. And, that the same thing must have happened again. At this point he thought that the new oxygen sensor must have gotten fried, so he had a new one delivered.
- The next step was to fix the oxygen sensor wiring. He tried rewiring it and noticed that the colors of the wires did not match the manufacturers schematic.
- My mechanic followed the wires all the way to the computer to ensure that he rewired them correctly. Still, the new oxygen sensor was not being seen by the computer. He was thinking that perhaps the oxygen sensor wiring is shorting out somewhere else in the wiring harness.
- This morning he called me to say that the 2 next options were: 1. run new wiring from the computer to the oxygen sensor or 2. buy a used computer from the junkyard. We went with #1.
- He called me this evening to tell me that with the new wiring from the computer to the oxygen sensor that the computer was still not seeing the new oxygen sensor.
- He is waiting to hear back from one of his colleagues who is a master mechanic with expertise in electrical.
I appreciate very much any feedback/comments/suggestions you may have.
Submitted: 1 year ago.
Category: Lexus
Expert:  Pete replied 1 year ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

If the computer was damaged internally due to the wiring shorting out (which is common to happen) then the computer itself will need replaced to correct this issue here.I have seen the computer damaged internally in the past before due to shorted wiring and had to replace the wiring section (which is best with this issue as a repair to oxygen sensor wiring will cause false oxygen sensor readings due to high resistance in the wiring) and replace the computer.I suspect the computer most likely needs replaced to correct this issue here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete.

Customer: replied 1 year ago.
Hi Pete! Thanks for your feedback. After finding out how much a new computer costs, my mechanic took another look at the wiring. He said that the insulation wiring (that goes to ground) melted into the oxygen sensor wiring. He removed it to test his theory and everything started working, computer was ok and seeing the new oxygen sensor. So, he put some new insulation wiring on along with some high heat resistant wrapping so that we don't run into this issue again. He was confident the issue was solved and I went to pick up my car last night. Then, this morning the same dashboard lights came back on! I have not brought it in yet to have him read the code. Any thoughts/suggestions/recommendations?Thanks,Chris
Expert:  Pete replied 1 year ago.

It is still possible the computer may have some sort of damage internally with it so it would be a good idea to have the mechanic first check and make sure all wiring is repaired properly and ground signals are secure and tight in case this is a poor ground issue.If all of this is o.k. there is a chance the computer itself still have internal damage needing replaced.

Thanks Pete