99 Es300 Cel And Trac Off Light And Multiple Codes

[kashi125]

Hi Everyone,

I recently had the Check Engine and TRAC OFF lights go off. Got codes read by AutoZone and they are:

P0125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

P1153 - Air/Fuel Ratio Sensor Circuit Response Malfunction (Bank 2 Sensor 1)

P1133 - Air/Fuel Ratio Sensor Circuit Response Malfunction (Bank 1 Sensor 1)

P1155 - Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

Over the last two days I have read every single post on this forum about these codes, but there is no comprehensive step-by-step list to troubleshoot them. I am hoping that through other people's help and my own experience of fixing this, I can make this post a useful resource for future readers. I will post updates as I go through troubleshooting this.

So, back to my problem. It is a 1999 ES300 with 150K miles. O2 sensors have never been replaced. I have a few questions:

1) Is it normal for multiple oxygen sensors to go bad simultaneously?

2) Is there a way to check to see if an oxygen sensor is working properly (resistance reading etc)?

3) Could all the other codes be due to a faulty thermostat (causing P0125)? I did notice that the engine temperature gauge on the instrument panel of this car sits way below the halfway mark when the engine is warm. On the other hand, in my 97 ES300, the gauge was almost at the halfway mark. Same with my 02 ES300.

4) Is there a way to check if the thermostat is working properly?

Thanks in advance for your help!

[George_Jetson]

The P0125 code is misleading, in the flow chart for troubleshooting the code it states that if there are any other codes present to fix those first.

So with that in mind, The easiest code to look at would be P1155, for the heater circuit. Since this is bank 2, (next to the rad) it is very easy to measure the resistance of the O2 sensor heater. Chances are you will find it open. If this is the case, I would stop at this point and purchase two O2 sensors. I purchase universal sensors, (I prefer bosch, many people like Denso sensors), with universal sensors, you need to re-use the connectors. I strongly recomend soldering the connections, and using heat shrink.

After you have replaced both sensors, clear you codes, and then see if any return. The first code is possibly caused by the others, and may not return once the other codes are fixed.

[kashi125]

George,

Thanks for your response and for leading me in the right direction. Based on your suggestion, I will ignore code P0125 for now.

Do you know what the normal resistance is supposed to be on the sensor heater? And how do I measure it (what terminals / wires)?

[George_Jetson]

o2sensor_check.pdf

Here, read this, it has a good description on how to check the heaters. If the front one is bad, my recomendation is to replace both bank 1, 1 and bank 2,1 sensors.

[kashi125]

Great, thanks a lot! I'll work on this tomorrow. As promised, I am updating the post with the steps I have taken so far.

STEP 1:

Erase codes in case it was a false CEL.

I erased them by disconnecting the positive battery terminal for 10 minutes. Started car, no CEL. But CEL came back after driving a couple of miles.

STEP 2:

Clean MAF (Mass Air Flow) Sensor.

I used CRC Mass Air Flow Sensor Cleaner purchased from Auto Zone for around $7. Cleaning is super easy. Locate the MAF sensor (on the air intake) and unplug the cable from it. The sensor comes off by taking off the two screws holding it to the intake. If you look down the tube in the sensor, you will see two metal wires. Mine were super dirty. After 3 or 4 sprays of the cleaner, they looked shiny as new. I also cleaned the temperature(?) sensor located on the outside of the MAF sensor. It is the round thingy connected to the plastic body of the sensor by two wires.

Let everything dry for about 15 minutes and then put the sensor back and attach the sensor cable.

Unplugged battery cable again to erase codes. Started car, no CEL. Drove 3 miles and CEL was back! However I must say that there was a significant difference in the pickup of the car after MAF cleaning.

Note: If I can find the specs of the MAF sensor I will take readings on mine and compare them just to make sure that it is indeed in working condition. A simple cleaning might not be enough to resurrect a dead sensor.

STEP 3:

Check the bank 2 sensor 1 heater. (This sensor is located right in front of you when you open the hood, between the radiator and the engine).

Sensor resistance is infinite (open circuit). Trying to decide whether to replace just this sensor or all the sensors.

STEP 4:

-- In progress --

[lenore]

I would not suggest using Bosch, for the Air fuel sensors. Many have installed them and still had the code a few days later. Use Denso only and save yourself some bucks. Most of the time you can not return the Bosch sensors (store policies)

[George_Jetson]

I would not suggest using Bosch, for the Air fuel sensors. Many have installed them and still had the code a few days later. Use Denso only and save yourself some bucks. Most of the time you can not return the Bosch sensors (store policies)

I am a little surprised that you seem to be firmly against the Bosch sensors. I have used them many times without issue,especially when you consider the fact that Bosch invented the O2 sensor, which also implies that they have the most experience making them. I realize that there are people having issues with the cars, especially such as a cat P0420 code, but I suspect that the underlying cause is not really the sensor.

[1990LS400]

I have used them many times without issue,especially when you consider the fact that Bosch invented the O2 sensor, which also implies that they have the most experience making them.

Ah ... the Bosch "Lamda Sond" ... brings back memories ... invented in 1976 and first used on 1977 Volvos. The Volvo 242 that I purchased in 1978 even had a Lamda Sond emblem on the front grill -- guess "Lamda Sond" sounded more impressive than "Oxygen Sensor".

You can see the Lamda Sond badge on the Volvo's grill in the attached photo -- my 78 242 looked the same ... even the same color which I called ... "Baby Poo".

[Shaun ES300]

My first post so forgive if I goof up. I have a 2001 ES300. Have CEL and Trac Off lights on. Firestone OBDII diag. says P1155 and P1135 and they concluded 2 AF sensors required to fix. ($670 total). Looking over this site, I've learned a little bit. I've diconnected B2S1 and measured resistance at AMB temp. Measures about 1.2 ohms. I see a pdf for 1997 ES300 stating higher resistance but think my '01 might indeed be correct at the lower resistance. The CEL's were for heater circuit malfunction so I expected to see O.C. if bad. Before go and buy 2 new sensors (I do have the correct Denso part located) can anyone advise to other trouble shooting before I drop $300 on the AF sensors?

Thanks,

Shaun

[George_Jetson]

I would suggest measuring the other O2 sensor. Also, have you checked the Heater fuse? The ECM provides a grd to the O2 heater, and measures the current. So if the fuse is blown, the computer will think the heater is bad.

$300 for 2 sensors? They are mightly proud of those sensors.

[George_Jetson]

Ps as far as the resistance being too low, you might want to go to radio shack and purchasing a resistor of the appropriate range. They cost about a dollar and can give you a reference to see if your meter is accurate.

[Shaun ES300]

I would suggest measuring the other O2 sensor. Also, have you checked the Heater fuse? The ECM provides a grd to the O2 heater, and measures the current. So if the fuse is blown, the computer will think the heater is bad.

$300 for 2 sensors? They are mightly proud of those sensors.

I've done a lot of checking and for a direct fitment AF sensor, $140 each is about as good as I could find. I want to check a fuse as you noted but don't know which one for the ES300. Can you provide specific location?

Thanks

[Shaun ES300]

Thought I read somewhere that resistance for the 2000/2001 AF heater circuit was lower ohms. I might have run across a pdf showing the resistance check but can't find it tonight. Thanks for the advice.

[George_Jetson]

According to my manuals, you are correct that the heater resistance is lower on 2000/2001. It appears that 0.6 to 1.8 is correct (or something like that), anyway the sensor you measured appears good.

So the next things are the A/F fuse, and A/F relay, both should be located in the power distribution box under the hood. I assume that the CEL came on a short time ago, so to have both sensor bad is unlikely. There is one fuse, and relay that supplies power to both sensors. The computer enables the relay, and supplies grds to the heater (while monitoring the current thru each heater).

The computer does not monitor if the relay actually is working, or the fuse is good, or any other possibility. On a positive note, the relay probably costs less than $20, and the fuse costs much less. Much better than $300, and easier to replace.

Be aware when you take your car to have the code read by places like firestone. The people reading the code do not have a lot of experience and do not really know exactly what the codes are actually telling them. You need to read the code, and then interpet exactly what it means. The computer can only determine what it sees at the inputs. If there is more than one component that is involved with supplying that single input the computer cannot distingish which part is bad. In your case, the computer cannot tell if the O2 sensor is bad, the relay, fuse, or the wires inbetween. All it knows is that the heater current is out of spec. The short version of the code description does not make this clear. You have to read the complete description.

[Shaun ES300]

According to my manuals, you are correct that the heater resistance is lower on 2000/2001. It appears that 0.6 to 1.8 is correct (or something like that), anyway the sensor you measured appears good.

So the next things are the A/F fuse, and A/F relay, both should be located in the power distribution box under the hood. I assume that the CEL came on a short time ago, so to have both sensor bad is unlikely. There is one fuse, and relay that supplies power to both sensors. The computer enables the relay, and supplies grds to the heater (while monitoring the current thru each heater).

The computer does not monitor if the relay actually is working, or the fuse is good, or any other possibility. On a positive note, the relay probably costs less than $20, and the fuse costs much less. Much better than $300, and easier to replace.

Be aware when you take your car to have the code read by places like firestone. The people reading the code do not have a lot of experience and do not really know exactly what the codes are actually telling them. You need to read the code, and then interpet exactly what it means. The computer can only determine what it sees at the inputs. If there is more than one component that is involved with supplying that single input the computer cannot distingish which part is bad. In your case, the computer cannot tell if the O2 sensor is bad, the relay, fuse, or the wires inbetween. All it knows is that the heater current is out of spec. The short version of the code description does not make this clear. You have to read the complete description.

Thanks George. Appreciate the info on the "ohm-age". I know where fuse box is but haven't a clue which fuse works this circuit. I'll try my trusty owners manual to see if it will help. Yes, the CEL came on last weekend and since I needed some service (fluids, rotate tires, etc) I asked Firestone to to a diagnostic. I agree, two AF sensors going out seems odd. (I do have 90Kmi, tho). Fortunately, I have a parking lift so I can get under the car to look at the other AF sensor and check it's resistance. So far, no poor gas mileage so I think my cat is safe for a little while.

[George_Jetson]

The cover to the power distribution box should be marked (on the inside), I believe it was app 20 or 25 amp fuse. Cats should be safe.

while you have it on the lift, look closely at the wires, the fuse may have just blown, or a wire could be melted onto the exhaust manifold, shorting the fuse out.

[Shaun ES300]

The cover to the power distribution box should be marked (on the inside), I believe it was app 20 or 25 amp fuse. Cats should be safe.

while you have it on the lift, look closely at the wires, the fuse may have just blown, or a wire could be melted onto the exhaust manifold, shorting the fuse out.

Checked fuse (25A) and it is good. Lifted the car and took a look at B1S1. Holy crap! I think I could remove the sensor but reaching up to disconnect the plug in connector looks rather daunting. Engine was too hot to reach up and try. Other priorities this weekend so I'll have to put off until later.

[kashi125]

Hi All,

I was out of town so didn't get a chance to do any more work on this. I'll update my post #5 with further steps that I take on this shortly.

Shaun, have you checked the voltage between HAFL / HAFR of ECM connector and body ground? (See attached screenshot).

[kashi125]

I checked the resistance on bank 2 sensor 1 heater and it is an open circuit. Since this sensor is definitely faulty, I have to replace it. Is it good practice to replace other sensors at the same time, even if they are OK?

[George_Jetson]

If your car has app 100k or more, I would suggest replacing both sensor 1's (bank 1 and bank 2). Since these are used for mixture control. O2 sensors are consumable items, I have always read that they should be replaced at app 60k. Of course I typically replace mine after they pass 100k. Very good possibility that you will see a increase in mileage.

[kashi125]

New sensors arrived today. I tried taking off the old sensor and it is seized in the manifold. After doing some research it seems like this is a common problem. I bought a can of PB Blaster and am going to spray close to the thread area and let it soak overnight.

Part numbers for reference (this is for a 1999 Lexus ES300):

Bank 1 (back of the engine, by the firewall) Sensor 1:

Toyota / Lexus part number: 89467-41021

Denso equivalent part number for this sensor is: 234-9007

Bank 2 (front, by the radiator) Sensor 1:

Old Toyota / Lexus part number: 89467-48010

New (improved) Toyota / Lexus part number: 89467-48011

Denso equivalent part number for this sensor is: 234-9009

I bought the Denso sensors on Amazon for $126 each and free shipping. Local Lexus dealer quoted $220 each and online Lexus dealer was $170 each.

[camlex]

both sensor are same. I bought from Toyota for $110 each. Call toyota for 99 V6 camry.

I replaced both at same time at 242K+ and O2 sensors are still works great at 360K+

[kashi125]

both sensor are same. I bought from Toyota for $110 each. Call toyota for 99 V6 camry.

I replaced both at same time at 242K+ and O2 sensors are still works great at 360K+

Yes, I think they are both the same except for wire length. One is 13" and one is 10".

wow you got a great deal at $110 each. Since you are in Houston too, which Toyota did you purchase at?

[camlex]

Sterling McCall

[Shaun ES300]

Sure taking this issue slow. I've checked my gas mileage and getting 22mpg in city so I guess that's reasonable. Thanks to this board for the advice about Advance Auto Parts. They ran a OBD-II check for me this afternoon and I only had a P1135 error code. Nothing else. If memory serves, that is the heater element for the B1S1 sensor (the really hard to reach one). If I can get my hands on the quick disconnect, I'll do a resistance check on it before taking further action. At least the OBD-II read from AAP checks with my earlier puzzel as to why B2S1 heater circuit measured as good functioning (grammar??)