01 Lexus RX-300

[charbaby]

I just replaced the original battery (almost 8 yrs old) today on my wifes 01 RX-300 as it seemed to be a bit weak and winter is on it's way. Everything runs fine with the new battery but, after about the 3rd restart while running errands today the "Check Engine and VSC lights displayed in the dash. This happened to me a couple of years ago as I had to disconnect the battery to clean the battery posts as a preventative maintenance. At that time, the dash lights came on during our driving but, went off after about a day. While installing the new battery today I was wondering if this would happen again and it did. Also today, I disconnected the ECU-B fuse for about 10 minutes. There is no ECU-A or PCM fuse so I don't know what other fuses to disconnect other than the EFI fuses. But the lights are out for now. I should mention that the ECU-B fuse is the one that I disconnected to reset the code when I installed a new o2 sensor(down stream just aft the cat conv) last year.
My question is; is there any reason that the CEL and VSC lights display on the dash when the battery is disconnected?
If there is any other information that I can provide, please let me know. If there is anyone that can explain this to me, this would be of great help and knowlage as Im a bit puzzled.

Thanks in advance

CB

 

[charbaby]

WOW!
I always seem to ask the hard questions.
I'll wait a couple of days to see if the lights
return on the dash display. If they do, I go to
AutoZone for a free diagnostic reading and see
what code numb3rs come up. I see that there are
45 views to my question. I know, it's a tough one.

Thanks All,

CB

 

[rg200amp]

I would go to auto zone and get the free scan. see if you have any temp codes.

If you have no codes, and the CEL is not on, id say your gravy.

 

[kazual]

The CEL is on for a reason and chances are you have no VSC. Get it scanned or just dissconnect and try again.

 

[charbaby]

Well like is mentioned earlier, I have pulled the fuse and all lights are out for now. If they don't return in a couple of days, Im sure that I'll be OK!

What I really think the problem is...I think that the Air Fuel Ratio Sensor(s) are lazy and I think that they have been lazy for some time(each time the battery is disconnected) but, remain working as long as there is an uninterupted source of power. Once the power is interupted, they trigger a code(dash lights on). Since I have already replaced the 02 sensor(damaged) Im going to rule out that one. On this vehicle, the AFR sensors(2) are in the exhaust manifolds(1 in each bank) and the 02 sensor(1) is down stream aft the cat. I'll see how thing go.

Thanx,

CB

 

[mechtech2]

Grounds are VERY important.
I'd clean both terminals and the interior of the cable ends.
Also look for additional grounds to the computer or frame.
At this point, get all power cables - both ends shiny clean.
Only grease or paint them AFTER assembly.

 

[charbaby]

mechtech2,
Thanks very much and an excellent idea but, the battery cable conectors have been cleaned prior to installing the new battery. They're perfect!
Please keep sending ideas. I'll rule out nothing unless I've already performed the task or replaced a part. As I mentioned, Im thinking that the(AFR) air fuel ratio sensor(s) are getting or have been lazy. This only happens when I tinker with the battery. If the dash lights return, I get the codes checked and start pricing parts so that I can replace them before the weather gets too bad. I will also check for other grounds as you mentioned.

 

[ChiTDI]

Char - he said Grounds! The other end of the negative post/cable. It may have several other ground wires leading from it. You clean where it attaches to the frame or body of the vehicle.

 

[ChiTDI]

There is a product called DeOxit 5 (I think) that provides protection and enhances the electrical connection. May have to Google to find it. Keeps the water out and prevents corrosion but also "provides" for current flow.
I'm no engineer, but this stuff is used on diesel platforms with great success. VWs are notorious for bad grounds.

 

[PT1]

There may be a reset procedure for the whole system. I know my RX330 has to be reset because the power windows & locks would not work if the battery was disconnected until they were reset. A Lexus dealer will know for sure.

 

[charbaby]

Originally Posted By: PT1
There may be a reset procedure for the whole system. I know my RX330 has to be reset because the power windows & locks would not work if the battery was disconnected until they were reset. A Lexus dealer will know for sure.


My Haynes Manual, (1999-2006 Highlander, RX-300 & RX-330), mentions what you have stated. But everything is working perfectly(windows, locks, sunroof etc.) I will certainly check the grounds as ChiTDI and Mechtech2 have mentioned.

 

[charbaby]

Well I have gone ahead and checked the grounds and both look A.O.K ! CE light has not returned yet.

 

[Johnny]

I would say if the light has not returned in six days, your good to go.

 

[charbaby]

Johnny, I agree! What I don't understand is why, when I disconnect the battery(for whatever reason) in this case, replacing the original, does the CEL and VSC lights display on the dash? My sister-in-law has the same exact year RX-300 and when her vehicle is serviced and the battey is disconnected(as/per requirement whenever working on the vehicle), she does not experience this. She knows that the battery has been disconnected because she has to reset the clock. She and I have discussed this. I have to investigate this a little further during better weather and really get into the ground wires. But, as I mentioned earlier, maybe one or more of the sensors are a bit lazy.

 

[charbaby]

Just came to me today!...Another way that I have ruled out the "ground issue"-- is that when Im driving at night, with these accessories on: head and driving lights, seat heaters, rear defroster, front defogger(which used the air conditioner for removing humidity). The head lights don't even dim a little bit when I come to a complete stop. If the ground(s) were at fault, I would notice something not right while driving with all accessories on. Also, when my SIL has her RX serviced and battery disconnected, Im wondering if the shop is resetting the PCM after reinstalling the battery cable and prior to my SIL picking up her vehicle and that's why she doesn't get the CEL???

Hmmmmm! I may be onto sometheing.