Check Engine Light On

[RX300MS]

Guys,

Need your help here. We got a 99 RX300 a month ago, and left it in the garage for about a month while we were trying to sell our other car. Last Thursday, I jumped it up and went out for some gas. On my way back home, I found that the engine check and TRAC OFF light were on. I went online and did some searches, and came back with different answers. I tried to tighten the gas cap and it did not help. During the weekend, we went for a 600 miles trip. The check engine light was on the whole time while thr TRAC OFF light went on just once.

It does smell abnormal, so I think the OS2 sensor is setting the light off, but I am not sure.

Can you guys give me any advise as to what to do now? Do I have to take it to the dealers or I can go to any auto parts stores for a check up?

Thanks for any help.

[GrahamC]

The most common cause on most vehicles for the CHECK ENGINE light is gasoline with too low an octane rating. Run the current tank as low as possible and then use at least 6 full tanks of 93 octane from multiple name brand stations. Try starting with Sunoco 94.

Remember, US gasoline is among the lower quality in the World. So don't skimp the pennies and use the best you can get.

[RX300MS]

Thanks, GrahamC. I think we filled it with 89. Will try to do what you said.

[RXKICK]

I disagree......The Rx330 will do fine on regular unleaded gas. You should check to see whether there are any recalls. Most likely the oxygen sensor went bad.

Also, make sure that your gas cap gasket is in good condition. Otherwise replace the cap and tighten it.

You didn't mention how many miles on your car?

RXKICK

[SKperformance]

i would say the gas thing is way off as well

the ecu does not show a code for octane level even if it knocks

it would have to be real bad

i might say the gas went bad, or you may have boosted it with a running car causing a power spike

[RX300MS]

It has 67K now.

I went to the GoodYear and had them checked on it. They said the bank 1 sensor went bad. They did a engine clean and told me to go back; and if the light comes back again, they will have to replace the sensor.

They said the sensor is 300 each. Geee. Wonder if there are any cheaper sensors for it.

Thanks, guys.

[Castrol]

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There are two (2) O2 sensors on the RX 300, one before the Catalytic Converter and one behind it. The front one is about $125 @ Autozone and the rear sensor is about $180. A special socket should be used to replace either O 2sensor. That socket can be rented at Autozone also.

Sometimes, a standard 7/8' box end wrench will work to replace O 2 sensors. Just unhook the signal wire to the sensor and then place the box end wrench over the old sensor to remove.

[SKperformance]

i think there are 3 o2 sensors

one in the fore and another in aft exhaust manifold banks and one after the cat

[lexus_romeo]

I have 44k miles on my 99 RX300. Chk engine light came on. Read all the posts in this forum. Took to Lexus dealer. Cost around $300 to have it fixed under warranty (I paid $0.) They said it was indeed the O2 sensors that failed. I tried tightening gas cap, etc., etc. before taking it down. Hope this helps.

[Castrol]

skperformance. You may be correct. Over the weekend, I'll check my shop manual. Thanks for the heads up.

[RX300MS]

Is the one right behind the cooling fan so called before catalyst? Could you guys confirm that? I am fixing to buy that one (bank 1 sensor 1, what the mechanic told me).

I did a search on google, but not much helpful. The oxygensensors.com only carry after catalyst. Went to advanced auto parts locally, they did not even ask me which sensor I need, just told me they carry two sensors (130 and 110$).

Thanks.

[SKperformance]

the ones in the engine bay are before the cat

as the cat is under the car a long rectangualr part of the exhaust usually under where the front seats are under the car

that sensor is about 3 inches back from the cat

and is usually chanegd by remomving the center console

[RX300MS]

thanks, skperformance.

I went to NAPA website too, it never asked me anything about before or after cat. It only listed two sensors (one with screw, one flange). So are the sensors (before, after cat.) the same?

Thanks again.

[daddyo]

I have this same problem with my 99 rx300 83k I just replaced the timing belt and waterpump. The check engine light and trac light came on later that same day? I'm going to take it this week to have the code read. any new updates?

Thanks in advance

Marty

[JPI]

DAddyo,

Your check engine is on because the tech miss a tooth on your timing belt. Timing belt on RX300 is kinna tricky the tech replaced your t belt didn't bother to line up with the marks. To answer everyone question, Bank 1 is by the firewall and bank 2 is in the front.

JPI

[RX300MS]

JPI, I guess I will have to bring it back to the mechanic to get the code now. Since you said bank 2 is in front, where as the mechanic told me is bank 1 which is front. And BTW, what is the fire ball?

And today, the "Trac Off" light came on again. The "Check Engine" light was always on.

Again, back to my question brought up yesterday, are the sensors before, after catelyst the same?

Thanks.

[JPI]

Hey there,

If he doesn't know which one is bank 1 then HE SHOULDN'T WORK ON YOUR CAR IN THE FIRST PLACE. Get the code and I will diagnost this problem for you. All you need is a 22mm wrench to replace this a/f sensor. These are the A/F(air fuel sensor). Firewall the bulkhead between the engine and the passenger compartment. The TRAC light is part of your check engine light.

These are the codes

Bank 1 sensor 1: P1130, P1133

Bank 2 sensor 1: P1150, P1153

Good luck and let me know.

JPI

[RX300MS]

Thanks, JPI. Fixing to get the code tomorrow from the mechanic. Meanwhile, if you could answer me these questions:

1. Just to make sure: the sensor between engine and cooling fan in the front, is it bank 1 sensor 1 or else? Is it after catalyst (fuel) sensor?

2. Is After Fuel the same as After Catalyst. I only saw the latter on the internet. And all the sensors I could find on internet, they either are "after catalyst" or they don't mention it at all.

3. Which one is the Before Catalyst (Fuel?) sensor? I heard that they are expensive, but never could find it on internet.

Thanks, I wish I was living close to Dallas, so I could drop by and let you to take a look. :P

Cheers.

[JPI]

1. Sensor in the front is bank 2 sensor 1. it's the before the cat. This a/f located on the exhaust manifold.

2. These two sensors are different. One is A/F and the other is O2 sensor.

3. Find out the code and I will tell you which sensor you will need. I can get parts at a discounted price.

Good luck.

JPI

[RX300MS]

JPI, I got the code from the mechanic. The code is P0420, Catalyst System Efficiency Below Threshold Bank 1. The mechanic said he was not sure which sensor went wrong, but he guessed it would most probably be the sensor in between cooling fan and engine which he said is bank 1 sensor 1. He said if it were him, he would replace it to see; but again he's not sure.

What do you say?

One more thing, the check engine light suddenly went off and is off now. Any idea?

Thanks, really appreciate your help.

[JPI]

Are there any other codes? If not you need to follow these steps. These are your trouble area: Gas leakage on exhaust system, A/F sensor (bank 1, 2 sensor 1), heateed oxygen sensor(bank 1 sensor 2), three-way catalytic converter.

- Check for gas leakage on exhaust system.

- Check A/F sensor (bank 1,2 sensor 1)these sensors on the exhuast manifold. Disconnect A/F sensor connector. Use an ohmmeter to measure the resistance between terminals +B and HT.

Resistance: at 68F 0.8-1.4ohms

at 1472 F 1.8-3.2ohms

- Check heated oxygen sensor(bank 1 sensor 2. This connector is located under the driver's

seat so you have to remove it. Use an ohmmeter measure the resistance between terminal +B and HT.

Resistance: at 68F 11-16ohms

at 1472F 23-32ohms

If these sensors are in spec then you need to replace your three-way catalytic converter. How come your mechanic doesn't test the sensors for you?

I hope this help. Most like you will need to bring your car to a lexus dealer to properly diagnost your RX. Or drive your car to dallas for me to diagnost :P .

JPI

[melschase]

I am new to this forum and I must say this is the most informative group I've seen yet!

I have a '99 Rx300 with ~88,000mi. I recently (1 week) found out I have a leak on my exhaust manifold. I think this "trips" my check engine light to turn on.

I'm pretty handy and by looking at the front manifold, it appears pretty straight forward in replacing this piece. 6 bolts where it attaches to the engine block and 2 that is connected to the downpipe.

Is this repair as easy as it appears to be? If so, any words of wisdom to make this a seemless swap? Another question, a friend mentioned that he thought this was a "recalled" item years ago. Does anybody know of this or is there a site I can review recalls for this year vehicle?

Again, keep up with the great advice. It's a fantastic vehicle and I'm glad that everybody is enjoying their RX. Thanks for your help!

[JPI]

On the older RX300, The cross over pipe usually break and cause the exhaust leak. Since then Lexus came out with a better design. If you want to find out where is the leaking coming from, get a rag and cover your exhuast tail pipe while your car is running. You will find your leak pretty quick. ;)

JPI

[JPI]

There wasn't any TSB for the cross over pipe. On the other note, You can use the scan tool to check your A/F sensor. I hope these will help.

JPI

[daddyo]

Thanks JPI and RX300MS for your input. My "tech" (who is very anal from working on mostly German cars) (he would only use a factory Toyota pump not the new made in Japan GMB pump that I supplied him from my friend that owns a parts store)

He checked the codes on Monday and came up with a problem with the bank1 O2 sensor, upon inspecton we also found that the exhaust manifold was cracked from the weld around the O2 sensor up the backside about 2-1/2" it also traveled down another 1" downward. I had the manifold welded and replaced the O2 sensor ($252.00 with discount from the dealer) (that hurt) and reset the comp. all is fine now. Ready for vacation on Sat.

Thanks Marty

99 Rx300 83k

95 BMW 525It