mackj

I purchased a 2000 Lexus RX 300 2 weeks ago. I didn't know it needed Premium gas so I put regular gas in. On the weekend I was on the highway and noticed it would not go into overdrive. When I searched online one of the main causes was the Knock sensors. Would the regular gas have triggered the knock sensors and if so, if I switch to Premium gas will that rectify the issue?

Baetke

I have a 1999 RX. It does not require premium gas but I run "plus" grade gas because I get significantly better mileage and performance over regular grade gas. I live in a state where we burn E10 gas (a.k.a. crap-gas). The ECU should be able to adjust for all fuel grades so I would check to make sure your knock sensors are working properly.

JAB

Are you certain that you had not unintentionally disabled the overdrive with the O/D switch?

thomas1

If the knock sensors were causing the problem, you would have a check engine light. Do you have this. If so you need to get the codes read. It could have been a coincedence......with the gas, you may have something else lurking...hopefully not a tranny failure...

mackj

I checked that the O/D off switch was not engaged. The check engine light is not on. Should I try disconnecting the battery or something like that?

salimshah

Does the CEL lightup before start position of the ignition key? At times the bulb can be blown and some sellers cheat the new buyer by disconnecting it.
[ref: see the owner's manual]

And CEL (in some cases such as knock sensor) can cause the O/D to be locked out. There can be other reasons too.

Clearing out the memory by disconnecting the battery has little harm. You will lose your memory settings and any pending emission codes.

Salim

mackj

I haven't noticed. So it should light up when I turn the key to the first stop (accessories)?

mackj

The CEL does not light up before starting. It must be burnt out.

salimshah

Time to get the codes read by an auto shop and investigate why the CEL does not light up before start.


Salim

mackj

Okay, thanks Salim.

mackj

.I got it checked. The codes are:
System too lean
left and right knock sensor malfunction
solar sensor cirtcuit passenger side.

salimshah

Now we know why OD is being locked out.

If you reset the CEL (by reader) or disconnecting the battery for a while (15 min or so) you should get the OD back .. till the CEL kicks in.

Any luck tracing the CEL bulb/wiring. If you bought the RX through a dealer you have some legal recourse.

The knock sensor replacement is involved [$1200 + @ dealer]. Check out the DIY.

The solar sensor impacts AC.

System lean ,, you have to search the actual code. Not sure if the knock sensor malfunction can impact this .. we try to solve one problem at a time.

Salim

mackj

The dealer says they will fix the o/d issue at their cost. I take it in on Monday. I'll report how that goes.

salimshah

Glad it worked out in your favor.

Did they give a reason why the CEL is not lighting up?

Salim

mackj

They did not but I am taking it in this morning and will ask them to fix that as well.