I was hoping someone can help me interpret some codes that I got recently on my '99 RX 300.

Initially I got:
P0125 - closed loop fuel ctrl, insufficient coolant
P1135 - fuel air metering
P0171 - system too lean
P1133 - fuel air metering

I then did some research here and found low coolant potentially could contribute to one of the codes (the coolant was a bit low so I added some) and I cleared the codes. The CEL did come back on about 5-10 mins of driving.

Rechecked the codes:
P0125 - closed loop fuel ctrl
P1135 - fuel air metering
P1133 - fuel air metering
P1130 - fuel air metering

the P0171 was no longer there

The car seems to drive fine without any problems noted. If my searching here is correct it seems most people have pointed to the A/F sensor for people with similar codes.

I must admit that the coolant has not been changed completely in quite some time. Does anyone feel the issue could be as simple as that?

I hope the board can help me troubleshoot here and direct me with a diy fix but if it seems that things overwhelmingly point to the AF sensor I will likely have the shop do that as that seems above my comfort level after reading how others have dealt with that.

Most importantly I just want to be more informed so that the shop doesn't take advantage of me and recommend the changing of all of the sensors (A/F, O2, thermostat etc...).

Thanks for your help.

 

The likely suspect here is the A/F sensor behind the engine block, aka bank 1, sensor 1. The only thing I can tell you is to get someone who has an advanced OBD2 scanner and see what readings are showing up. I tell you, those OBD2 scanners (or a laptop program like Elmscan 5) pay for themselves. Some mechanics will even have a software or scanner that will show a freezeframe of the situation when the actual codes showed up (you can see like fuel trims, the reading on the A/F sensors, etc.) and that can further pinpoint the troubles.

 

Sometimes it is better to clear all codes and read them again [the intent is to capture the first reported problem].

Salim

 

Thanks for the comments. Maybe I will have to read again about the replacement of the A/F sensor to see if it is worth my frustration to save some money.

Salim- Thanks for your input. The second set of codes I listed was read shortly after clearing the codes with unplugging the battery technique.

Any other advise is appreciated but I may have a date with the local Toyota dealer this week.

Thanks.

 

Lexmex, Salim or others -

Could someone just please clarify the different sensors (air flow vs oxygen sensor) and the location of each. Most posts seem to refer to the air flow sensor (the perceived problem I am having?) as being under the car. Other posts call the sensors under the hood as AF as well. Just hoping for some clarification.

Thanks.

 

PF-It isn't actually "air flow", it's "air/fuel" sensor. A lot of books and even parts people still use the terms "oxygen sensor" and "air/ fuel sensor" alternately and nothing could be farther from the truth and it causes the average car owner a lot of confusion. What you have on the engine (and what you have the codes for) are "AIR/FUEL RATIO SENSORS" The 3 codes are ALL for the one at the rear of the engine (firewall side) You do have an OXYGEN sensor, but that is the one under the car and you don't have codes for that, and you seldom ever have problems with that.

The P0125 code is here: http://www.obd-codes.com/p0125 I agree with Lexmex, the best way to find out EXACTLY what is actually going on is exactly what he posted. I am not really convinced that the A/F ratio sensor (B1S1, at the rear of the engine) is actually bad, with 3 codes all coming up at once and involving the heater as well as the sensor operation, which are separate issues. Could be, but suspect. I would also suggest that you change the coolant and use ONLY RED TOYOTA COOLANT, not something that claims to be equivalent. Aluminum is MUCH more subject to catastrophic corrosion erosion if the anti-corrosives are allowed to deplete from age than cast iron is. It can easily cost you an engine.

P.S. the rear A/F ratio sensor has to be reached from under the car, at the rear of the engine, not to be confused with the oxygen sensor under the drivers seat.

 

Yes I did mean Air/Fuel. Thanks for correcting me. Sounds like I'll take it to the Toyota dealer and get the coolant replaced and get their interpretation of the codes and if they suggest much above the A/F sensor perhaps I will be suspect.

Thanks for all of the great help.

 

Let me show some pictures.

Below is the one that we are specifically referring to in your case, the Bank 1, Sensor 1 A/F (Air/Fuel Sensor), which is behind the engine block.

 

Next one is the Bank 2, Sensor 1 A/F (Air/Fuel Sensor), which is clearly visible when you open the hood and look on the front of the engine block and behind the cooling fans.

 

Here is Bank 1, Sensor 2, an O2 sensor (oxygen) related to the function of the catalytic converter, which is below the vehicle and behind the catalytic converter.

 

There is something called a MAF Sensor (Mass Air Flow) and this is located in your engine bay and is on the tube coming from the black air box. This picture is going to be a bit different since I have a modified intake, but the part is the same.

 

Just an update to my problem.

I did get the coolant changed by the dealer yesterday and car was acting fine. I then was going to finish the trouble-shooting of the CEL more locally. This am driving to work everything drove fine.

Today at lunch on a trip back from the market the car stopped acclerating normally. Would only drive at a certain low speed despite how far the pedal was pressed but if I floored it the car did take off.

Sounds like the transmission is bad but seems coincidental after just having it serviced (albeit coolant).

Is there anything that might have gone wrong with the coolant flush and fill that could give me these new symptoms? Or is it related to the sensor problems that previously posted?

Or do I have a brand new transmission problem?

Thanks

 

Do check the coolant level yourself as it can sometimes go down a bit after being changed out (but that's very probably not the issue here).

I need to know more about the mph, etc. that this is occurring, i.e. describe say from a stoplight and going forward what's happening at what mph.

 

Lexmex,

It will go about 10-15 mph with normal acceleration from stop then will need to 'peddle' it (press firmly down on the gas) when it quickly accelerates to 'normal' operation but when you have to slow down to make a turn it will then restart at the low speed until you 'peddle' it again.

I did check coolant level after about a 20 min drive back from the dealer yesterday and that was fine.

Thanks.

 

I'd check the transmission level and see if it is low That sounds a bit like 'surging' which often makes it difficult to switch gears.