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1999 Rx300 - Codes P0125 And P1155


Harry_4
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Hi,

I am new to this forum. lately I have had a sudden problem with my 1999 RX300 with 86,000 miles and am not sure what to do next. Just last week, I had more than $3,500 worth of work on on this vehicle. This included replacing ignition coils 1 and 2 (as I was told that there was misfiring and these 2 were dead), water pump, timing belt tensioner, thermostat, exhaust manifold and gasket. I also had the 90,000 mile service done, which included EFI/Carbon Clean service, oil change, air filter, spark plugs, etc.

Immediately after the above repairs and service, as I drove out, I got the Check Engine sign again. I took it back to the shop. At that time the error code was P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control ). He reset it and we went for a test drive. within 5 miles we got the engine check light again. This time the error code P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) ). He estimated another $500 worth of repairs.

My questions:

1. Would all the initial repairs cause these new problems? Like replacing the exhaust manifold, or anything else?

2. How much should I spend to fix the codes P1155 and P0125?

3. Can these 2 codes have an easier fix (like cleaning, etc) rather than replacing them?

4. The repairs were done at a shop that claims speciality in SUVs. Should I take it to the dealer?

At this point, the Check Engine light stays on. Thanks in advance for your comments and suggestions.

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Hi,

I am new to this forum. lately I have had a sudden problem with my 1999 RX300 with 86,000 miles and am not sure what to do next. Just last week, I had more than $3,500 worth of work on on this vehicle. This included replacing ignition coils 1 and 2 (as I was told that there was misfiring and these 2 were dead), water pump, timing belt tensioner, thermostat, exhaust manifold and gasket. I also had the 90,000 mile service done, which included EFI/Carbon Clean service, oil change, air filter, spark plugs, etc.

Immediately after the above repairs and service, as I drove out, I got the Check Engine sign again. I took it back to the shop. At that time the error code was P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control ). He reset it and we went for a test drive. within 5 miles we got the engine check light again. This time the error code P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) ). He estimated another $500 worth of repairs.

My questions:

1. Would all the initial repairs cause these new problems? Like replacing the exhaust manifold, or anything else?

2. How much should I spend to fix the codes P1155 and P0125?

3. Can these 2 codes have an easier fix (like cleaning, etc) rather than replacing them?

4. The repairs were done at a shop that claims speciality in SUVs. Should I take it to the dealer?

At this point, the Check Engine light stays on. Thanks in advance for your comments and suggestions.

Absent knowing, having a LONG service history with the non-marque shop involved, I would NEVER take a modern high technology vehicle to a third party shop.

In short, you've just been screwed.

Now take it to Bellevue Lexus and get screwed yet again.

But at least you'll get the car fixed properly.

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Hi,

I am new to this forum. lately I have had a sudden problem with my 1999 RX300 with 86,000 miles and am not sure what to do next. Just last week, I had more than $3,500 worth of work on on this vehicle. This included replacing ignition coils 1 and 2 (as I was told that there was misfiring and these 2 were dead), water pump, timing belt tensioner, thermostat, exhaust manifold and gasket. I also had the 90,000 mile service done, which included EFI/Carbon Clean service, oil change, air filter, spark plugs, etc.

Immediately after the above repairs and service, as I drove out, I got the Check Engine sign again. I took it back to the shop. At that time the error code was P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control ). He reset it and we went for a test drive. within 5 miles we got the engine check light again. This time the error code P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) ). He estimated another $500 worth of repairs.

My questions:

1. Would all the initial repairs cause these new problems? Like replacing the exhaust manifold, or anything else?

2. How much should I spend to fix the codes P1155 and P0125?

3. Can these 2 codes have an easier fix (like cleaning, etc) rather than replacing them?

4. The repairs were done at a shop that claims speciality in SUVs. Should I take it to the dealer?

At this point, the Check Engine light stays on. Thanks in advance for your comments and suggestions.

Absent knowing, having a LONG service history with the non-marque shop involved, I would NEVER take a modern high technology vehicle to a third party shop.

In short, you've just been screwed.

Now take it to Bellevue Lexus and get screwed yet again.

But at least you'll get the car fixed properly.

Well, it is unsettling to find out that I have been screwed. These guys did come across as honest. You might be right and I might have no choice but to take it to the dealer. Unless someone can suggest something different?

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Hi,

I am new to this forum. lately I have had a sudden problem with my 1999 RX300 with 86,000 miles and am not sure what to do next. Just last week, I had more than $3,500 worth of work on on this vehicle. This included replacing ignition coils 1 and 2 (as I was told that there was misfiring and these 2 were dead), water pump, timing belt tensioner, thermostat, exhaust manifold and gasket. I also had the 90,000 mile service done, which included EFI/Carbon Clean service, oil change, air filter, spark plugs, etc.

Immediately after the above repairs and service, as I drove out, I got the Check Engine sign again. I took it back to the shop. At that time the error code was P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control ). He reset it and we went for a test drive. within 5 miles we got the engine check light again. This time the error code P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) ). He estimated another $500 worth of repairs.

My questions:

1. Would all the initial repairs cause these new problems? Like replacing the exhaust manifold, or anything else?

2. How much should I spend to fix the codes P1155 and P0125?

3. Can these 2 codes have an easier fix (like cleaning, etc) rather than replacing them?

4. The repairs were done at a shop that claims speciality in SUVs. Should I take it to the dealer?

At this point, the Check Engine light stays on. Thanks in advance for your comments and suggestions.

Hi Harry- To begin with I believe you will find that P1155 is Bank 2 Sensor 1, which would be the front 1 on the exhaust manifold straight down when you open the hood. P1135 would be for Bank 1 Sensor 1- in the rear. The 1 Lexus specific code chart I checked has an error there. If they are quoting you $500.00 for just replacing that sensor that is pricey to say the least. I replaced both of them on my DIL's 99RX300 and was able to get them from a Toyota dealer for $162. ea. plus tax and could have gotten them from a Lexus dealer online for $150. ea. plus shipping and tax (Ca.) if I had had the time to wait. They only list from Toyota for a little over $200. ea. Secondly, the P0125 lists 1. Insufficient warm up time 2. Leaking or stick open thermostat 3. Faulty coolant temperature sensor 4. Low engine coolant level There are other things that can cause the P0125 and I reluctantly have to agree with the earlier poster that often the dealer (stealer) has a better handle on pinpointing the problems than an independent. You just have to bend over and grab your ankles, but I'm not absolutely sure you haven't had to do that already with the independent. Best of luck and let us know how things turn out. Y/T- Roger

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Hi,

I am new to this forum. lately I have had a sudden problem with my 1999 RX300 with 86,000 miles and am not sure what to do next. Just last week, I had more than $3,500 worth of work on on this vehicle. This included replacing ignition coils 1 and 2 (as I was told that there was misfiring and these 2 were dead), water pump, timing belt tensioner, thermostat, exhaust manifold and gasket. I also had the 90,000 mile service done, which included EFI/Carbon Clean service, oil change, air filter, spark plugs, etc.

Immediately after the above repairs and service, as I drove out, I got the Check Engine sign again. I took it back to the shop. At that time the error code was P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control ). He reset it and we went for a test drive. within 5 miles we got the engine check light again. This time the error code P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) ). He estimated another $500 worth of repairs.

My questions:

1. Would all the initial repairs cause these new problems? Like replacing the exhaust manifold, or anything else?

2. How much should I spend to fix the codes P1155 and P0125?

3. Can these 2 codes have an easier fix (like cleaning, etc) rather than replacing them?

4. The repairs were done at a shop that claims speciality in SUVs. Should I take it to the dealer?

At this point, the Check Engine light stays on. Thanks in advance for your comments and suggestions.

Absent knowing, having a LONG service history with the non-marque shop involved, I would NEVER take a modern high technology vehicle to a third party shop.

In short, you've just been screwed.

Now take it to Bellevue Lexus and get screwed yet again.

But at least you'll get the car fixed properly.

Wow. This is one of the worst hosings I've heard about in a long time. At 86k miles, I seriously doubt you needed a new tensioner, thermostat, carbon clean service, exhaust manifold or new plugs. At 83k, the original spark plugs on my RX look brand new. Did they show you the old tensioner and explain what was wrong with it? Why did they replace the exhaust manifold? Was the water pump bearing showing signs of failure or did they replace it just to be safe? Did they get your approval in advance?

Regarding the new work, P0125 & P1155 together indicate you need a new Bank 2 Sensor 1 (A/F) which will cost about $150 for a quality aftermarket Denso. It should take less than 1/2 hour to install it. Yes, IMHO, their work almost certainly caused the A/F Sensor failure although I had an A/F Sensor fail on my Avalon (also has the 1MZFE engine) at less than 85k miles. Just too much of a coincidence that yours failed right after they assaulted your RX. P0125 & P1155 codes together indicate the heater circuit in you Bank 2 Sensor 1 is shot. Did they replace the Bank 2 exhaust manifold? Could be something as simple as they forgot to reconnect the B2S1 and they want to charge you $500 to do a 5 second job. You can confirm the B2S1 heater circuit is fried with a 15 second ohmeter check.

A shop claiming specialty in SUV's is like finding a doctor who specializes in parts above the waist. Pretty meaningless claim.

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Hi,

I am new to this forum. lately I have had a sudden problem with my 1999 RX300 with 86,000 miles and am not sure what to do next. Just last week, I had more than $3,500 worth of work on on this vehicle. This included replacing ignition coils 1 and 2 (as I was told that there was misfiring and these 2 were dead), water pump, timing belt tensioner, thermostat, exhaust manifold and gasket. I also had the 90,000 mile service done, which included EFI/Carbon Clean service, oil change, air filter, spark plugs, etc.

Immediately after the above repairs and service, as I drove out, I got the Check Engine sign again. I took it back to the shop. At that time the error code was P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control ). He reset it and we went for a test drive. within 5 miles we got the engine check light again. This time the error code P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) ). He estimated another $500 worth of repairs.

My questions:

1. Would all the initial repairs cause these new problems? Like replacing the exhaust manifold, or anything else?

2. How much should I spend to fix the codes P1155 and P0125?

3. Can these 2 codes have an easier fix (like cleaning, etc) rather than replacing them?

4. The repairs were done at a shop that claims speciality in SUVs. Should I take it to the dealer?

At this point, the Check Engine light stays on. Thanks in advance for your comments and suggestions.

Absent knowing, having a LONG service history with the non-marque shop involved, I would NEVER take a modern high technology vehicle to a third party shop.

In short, you've just been screwed.

Now take it to Bellevue Lexus and get screwed yet again.

But at least you'll get the car fixed properly.

Wow. This is one of the worst hosings I've heard about in a long time. At 86k miles, I seriously doubt you needed a new tensioner, thermostat, carbon clean service, exhaust manifold or new plugs. At 83k, the original spark plugs on my RX look brand new. Did they show you the old tensioner and explain what was wrong with it? Why did they replace the exhaust manifold? Was the water pump bearing showing signs of failure or did they replace it just to be safe? Did they get your approval in advance?

Regarding the new work, P0125 & P1155 together indicate you need a new Bank 2 Sensor 1 (A/F) which will cost about $150 for a quality aftermarket Denso. It should take less than 1/2 hour to install it. Yes, IMHO, their work almost certainly caused the A/F Sensor failure although I had an A/F Sensor fail on my Avalon (also has the 1MZFE engine) at less than 85k miles. Just too much of a coincidence that yours failed right after they assaulted your RX. P0125 & P1155 codes together indicate the heater circuit in you Bank 2 Sensor 1 is shot. Did they replace the Bank 2 exhaust manifold? Could be something as simple as they forgot to reconnect the B2S1 and they want to charge you $500 to do a 5 second job. You can confirm the B2S1 heater circuit is fried with a 15 second ohmeter check.

A shop claiming specialty in SUV's is like finding a doctor who specializes in parts above the waist. Pretty meaningless claim.

I don't know what you do for a living "artbuc" but that is a very perceptive post. I am always glad to see TRULY knowledgeable help like this extended to those that need the help. Congratulations!

The P1155 (front a/f ratio sensor) is a 15 min. job and can be checked with a Dvm as artbuc said. My only suggestion would be that you only use ORIGINAL EQ. Denso which you can buy from the right source for that amount. Denso does make aftermarket sensors and the ones I tried did not work. I feel there is a chance that if they changed the front manifold and either dropped the sensor or were a little rough with it they could have broken the heater element. They run at a very high temp when they are on and therefore could become brittle over time.

The W/P, tens.,spark plugs and possibly other parts are parts that Lexus would recommend you change at those miles are not parts that necessarily need to be changed because of end of life issues. I have dealt with all of these issues on my DIL's RX300 and I can say that at 97k though I changed them (some of them) for some very specific reasons, most were not worn out by any means. (I have spent my life in automotive work-just as a background) All parts were original and the timing belt showed NO signs of wear or cracking at that age. The plugs were in remarkable shape for 97k. The w/p as well as tens. pully were smooth as new and NO sign of leaking. If your wallet is fat and you chose to by all means change them, but not because they are necessarily at the end of their life.

2 coils dead? That thing must have hardly run. I'm not saying these people were dishonest, but at the cost of auto repairs today, it upsets me that there are not more TRULY HONEST shops, treating people like they were spending THIER money rather than YOURS!. Again, thanks "artbuc" for the knowledgeable and competent councel you gave Harry, Y/T- Roger

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  • 3 years later...

P0125 Insufficient Coolant Temp. for Closed Loop Fuel Control. I've read a lot of forums about people saying this is a coolant temp sensor or thermostat, but TIS (Toyota Information System) says that is has to do with an A/F (air/fuel ratio) sensor. Here is the condition and trouble area directly from TIS. (I've worked for Toyota and Lexus for a few years and have access to to TIS);

DTC Detecting Condition; P0125 After the engine is warmed up, A/F sensor output* does not change when conditions (a), (, and © continue for at least 1.5 min.

*: The output value changes at the inside of the ECM only.

(a) Engine speed: 1,500 rpm or more

( Vehicle speed: 40 ∼ 100 km/h (25 ∼ 62 mph)

© Throttle valve does not fully close

Trouble Area;

Open or short in A/F sensor circuit (bank 1, 2 sensor 1)

A/F sensor (bank 1, 2 sensor 1)

ECM

DTC P1155 A/F Sensor Heater Circuit Malfunction (Bank 2 Sensor 1) (the front of the motor, upstream sensor)

If you open the hood and look straight down at the exhaust manifold, that's the sensor that's faulty.

DTC Detecting Condition;

Heater current of 0.25 A or less when the heater operates (2 trip detection logic)

Trouble Area;

Open or in heater circuit of A/F sensor

(bank 1, 2 sensor 1)

A/F sensor (bank 1, 2 sensor 1) heater

ECM

DTC P1150 A/F Sensor Circuit Range/Performance

Malfunction (Bank 2 Sensor 1)

CIRCUIT DESCRIPTION

Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control)

Open or short in A/F sensor (bank 1, 2 sensor 1) circuit

A/F sensor (bank 1, 2 sensor 1)

ECM

You may as well replace both A/F sensors because if the one on the front of the car is faulty then the other one towards the rear of the car is probably right behind it. We replaced our b2s1 a/f sensor, then the motor went t*ts up and I had to replace/rebuild another motor. The vehicle was down for quite a few months while I did this. I just got it running a couple months ago now we have a P0125 and P01135 codes, now we have to replace the rearward a/f sensor (which is bank 1 sensor 1). The sensor on the front of the car, top of the motor is bank 2 sensor 1

Hope this helps.

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  • 9 years later...
On 11/28/2011 at 12:53 PM, OneSicSRT said:

P0125 Insufficient Coolant Temp. for Closed Loop Fuel Control. I've read a lot of forums about people saying this is a coolant temp sensor or thermostat, but TIS (Toyota Information System) says that is has to do with an A/F (air/fuel ratio) sensor. Here is the condition and trouble area directly from TIS. (I've worked for Toyota and Lexus for a few years and have access to to TIS);

DTC Detecting Condition; P0125 After the engine is warmed up, A/F sensor output* does not change when conditions (a), (, and © continue for at least 1.5 min.

*: The output value changes at the inside of the ECM only.

(a) Engine speed: 1,500 rpm or more

( Vehicle speed: 40 ∼ 100 km/h (25 ∼ 62 mph)

© Throttle valve does not fully close

 

Trouble Area;

Open or short in A/F sensor circuit (bank 1, 2 sensor 1)

A/F sensor (bank 1, 2 sensor 1)

ECM

DTC P1155 A/F Sensor Heater Circuit Malfunction (Bank 2 Sensor 1) (the front of the motor, upstream sensor)

If you open the hood and look straight down at the exhaust manifold, that's the sensor that's faulty.

DTC Detecting Condition;

Heater current of 0.25 A or less when the heater operates (2 trip detection logic)

Trouble Area;

Open or in heater circuit of A/F sensor

(bank 1, 2 sensor 1)

A/F sensor (bank 1, 2 sensor 1) heater

ECM

DTC P1150 A/F Sensor Circuit Range/Performance

Malfunction (Bank 2 Sensor 1)

CIRCUIT DESCRIPTION

Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control)

Open or short in A/F sensor (bank 1, 2 sensor 1) circuit

A/F sensor (bank 1, 2 sensor 1)

ECM

You may as well replace both A/F sensors because if the one on the front of the car is faulty then the other one towards the rear of the car is probably right behind it. We replaced our b2s1 a/f sensor, then the motor went t*ts up and I had to replace/rebuild another motor. The vehicle was down for quite a few months while I did this. I just got it running a couple months ago now we have a P0125 and P01135 codes, now we have to replace the rearward a/f sensor (which is bank 1 sensor 1). The sensor on the front of the car, top of the motor is bank 2 sensor 1

Hope this helps.

After doing research and verifying what you said I also came to conclusion that the oxygen sensor should be changed first witch I ordered original. I had my whole exhaust replaced and these two front sensors are denso so I just soaked them in some fuel additive to try to clean the tips. Not sure if this ruined them but I wanted to try this because I was getting a o2 code and eventually it went away. At the time I didnt wanna replace them because of the price and the code was not coming up. Now I am getting same codes you got. I am going to replace the one in the front but do I need to replace the 2nd one or can I wait to see if the check engine light stays off after and just drive it. They are both denso but not sure how old they are and I did take them out and soaked the tips with the holes in a gass additive over night to see it that helped. I definately think I need to change the fron one because of the code but starting to think i should change the 2nd one to cause I soaked it in additive and may  have messed with it or should I just drive it after changing the one? 

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