brijinder

All codes are related to bank 1 sensor 1 and bank 2 and sensor 1 for slow response and circuit malfuntion. Now the weird thing is that both oxygen sensors are changed at 102XXX miles by previous owner of the car and how both can fail at same time and so soon ? Car currently has 116XXX miles. I read somewhere that changing air filter can help so I did it today but check engine light is still on. Did anyone faced this kind of issue or any idea. Please let me know.

brijinder

Any idea ?

mdbrown

Would need to know first if the sensors are lexus/toyota or aftermarket. If they are aftermarket that is probably the issue.

Steelfan

http://bahamutcars.free.fr/workshop/.../m_di_0118.pdf

Here is the diagnostic work flow. For a GS but should be the same for the ES.

I bought DENSO aftermarkets for an ES300 and they worked fine but DENSOs are also the OEM brand. Almost a $100 difference b/w the cost for each one. I got mine at NAPA.

brijinder

Thanks mdbrown and steelfan for the reply.

As per service record of the previous owner, 2 front oxygen sensors are replaced and the part number is 89465-06100 which I googled and seems to be Toyota original part.

mdbrown

Have seen this before, turned out the technician stripped the threads so the sensor did not fit tight... check the sensors for proper fit.

Steelfan

Since these are on the manifolds, if they aren't fitting properly, you'll probably hear an exhaust leak.

I stripped out the Bank 1 sensor next to the firewall when pulling it out. Used the old Bank 2 sensor (since I had to replace both) to rethread the hole.

You can pull the sensors and check the resistance per the work flow above to check the heater circuit. You need to do some other things to check out the actual "sensor."

brijinder

Thanks Steelfan.

I have ordered a code reader and I will read the frame freeze data. Maybe that will help in getting more information.

brijinder

So I went to mechanic today to check it. He ran a smoke/vacuum test on the car and found out that the smoke is coming out of the vacuum brake booster.
He is telling me that brake booster needs to be replaced. It seems to be expensive part. Thinking of getting check from one more mechanic. Let me know if somebody faced this issue.

mdbrown

Well, it's certainly possible. With the engine running try stepping down on the brake pedal real fast. Typically it will be hard to do if the booster is leaking. A leaking brake booster can cause a lean running/lean misfire condition. Easiest would be to cap off the line going to the brake booster, clear the codes and see if they come back. Most brake boosters have a check valve in the line to prevent this sort of thing though.

brijinder

Thanks mdbrown for info. So you are saying to take out the air hose going into the booster and clear the codes ? Do I need to also block the hose which is going to the other side towards the engine ?

mdbrown

Yes, disconnecting the hose creates a huge vacuum leak. Cap the hose and see what happens.

brijinder

I tried to disconnect the hose and cap it off, but when I tried to apply brake on running car, the brake became too hard to apply so I gave it up. Anyways, what I did alternatively is cap the hose and read the live oxygen sensor voltage on obd scanner and noticed that voltage was switching between 0.4 to 0.5 at rapid pace and it was around 0.0015V and ultimately went to 0V when hose is connected to brake booster. Through this test, I was almost sure that brake booster is having problem. Today I got brake booster replaced and after driving 40-45 miles, the check engine light didn't come on. This problem was kind of hard to detect and I asked some really good mechanics that I heard in my area and they said that it can't be a brake booster issue and suggested me to change oxygen sensors instead, inspite of telling them that they are changed recently less than 14K miles and they are OEM toyota

BTW, I purchased this Ecan scanner (http://www.amazon.com/ElmScan-Compac...4573805&sr=8-2 ) and used Easy Obd software with it and I really liked it.

I will update the thread if CEL comes it on again.