jerbear

My wife has a 1999 4Runner 3.4, with an automatic transmission. No major mods, just a K&N air filter. The other day the CEL came on and I sent her to advance to have the codes pulled. I got the following readout from them.

DTC (Codes)

P0125
CLSD Loop Fuel CTRL
Insufficient
Coolant Temp

P1135
Manufacurer Contrl.
Fuel Air Metering

DTC Pending (Codes)

P0171
System Too Lean
(Bank 1)

P1135
Manufacurer Control.
Fuel Air Metering

I know that the P0171 can be a dirty MAF as I am running an oiled filter, in fact the last time the CEL came on the good people of this board directed me there and it has solved the problem for quite some time. But last time that was the only code. Now there are four. I have searched the codes individually here, but I figured that I should post them as a group to see what the general consensus might be. The vehicle has 168,000 miles on it. I have also noticed that it will lose a little coolant from the radiator, but there are no drips or leaks. I parked the car on a full sheet of cardboard for two days and there was nothing on it. Even ran the vehicle for about 30 minutes. Again the loss is less than 8oz after a few thousand miles, but I figure I should put it in here. Thank you in advance for your help.

jerbear

I put this in the wrong section. Please move to the section for 1999 4runners.

mt_goat

Well I'm thinking the last 3 could all be related to a dirty MAF. Get rid of that dang K&N, they suck at filtering and they mess up your MAF. Try cleaning the MAF with electrical contact cleaner, but DON'T touch the wire with anything.

Small coolant leaks can be tough to spot because the system usually only leaks while under pressure and that's usually only while driving. Try looking around the bottom of the radiator right after driving for a while. Look closely at the seam in the radiator where the plastic ends (or tops?) meet the metal core.

toyota_mdt_tech

You basically need an AF ratio sensor. And clean the MAF sensor wi th brake cleaner. Careful, yours has a AF sensor, not an O2 sensor.

mt_goat

Here's a good source for A/F sensors if you need one: http://www.urdusa.com/product_info.p...s_id=430006000

jerbear

Thank you for the replies. One post states that I need an A/F Sensor not an O2 sensor and then another post say go to URD and states that page lists O2 sensors. Are they the same sort of thing? Are they in the exhaust stream and which one is it? The first, closer to the engine or the second? Thank you for all the help. Should I send URD my VIN to make sure I get the right one? Thanks again, you folks are the best.

toyota_mdt_tech

The AF ratio sensors in your California emissioned 99 4Runner will alway belocated in front of the catalytic converter. After, your rig uses the same O2 sensors as all others. The P1135 is for AF ratio sensors on Cally emissions in 1999. So when getting the parts, they should ask you what you have, if they dont, go away and find someone who does, otherwise, they will sel you a conventional O2 sensor and you will be back to square 1, except a little less $$$ in your checking account, as there is usually "no return on electrical". It will also cure your P0125 code too, but the P0171 is a seperate issue possibly, but do the sensor first, clear codes and see if anything comes back

mt_goat

The A/F sensor is a highly sensitve and accurate O2 sensor but it is still technicaly an O2 sensor. Many people call it a different name to avoid mixing them up (they are not interchangeable) URD knows what what they are doing and are well aware of what year/model trucks/4runners need what sensor as you can tell by their detailed list. They sell the same OEM sensors you would get from the dealer (but cheaper). It is the front sensor. URD probably won't need your VIN#.

The rear sensor is only used to measure how well the cat/cats are doing their job and have no effect on performance. The front sensor is used by your ECU to adjust your air/fuel ratio (A/F).

slater442w30

The very first thing I would do, change the thermostat, then test the ect switch for the coolant, your first code means the computer in the truck thinks that the truck is running cold all the time, even after it warms up, that can cause more problems like you are describing. The rest of the engine is warm, but the brain is telling the engine "I am cold so run like I am cold" causing all kinds of problems. I have the pleasure of diagnostic tools and factory service manuals, might be worth taking to a shop or a friend with the tools to test the sensors the right way before you start throwing money at it. We get a lot of cars in with the same symptoms and this is how we start the repair process, and it usually ends up with good results. If you need to know how to test the switch or need numbers for the readings the switch should be putting out I can get them from the computer at my shop.
Good luck.

toyota_mdt_tech

That insuffeceint coolant temp code has nothing to do with the coolant temp, but more to do with the AF ratio sensor. I forget the exact details, but it referes back to the sensro itself.

slater442w30

Okay I got the fsm out, the first code on his list.
His first is a bad oxygen sensor or bad sensor heating circuit, so yes I was wrong, an integra I fixed last week had a ver similar code, and had a bad stat in it and wasnt warming up, this is a different story. Yes, check the air flow meter, get rid of the K&N (I need to do that too) also check for bad vacumn hoses near bank 1 of the engine, and did you ever erase the memory of the ecm from last time you had problems? how is your fuel filter? I would clear the codes, clean or replace the maf and drive it and see what comes back up. That is the cheapest easiest thing you could do to fix it without paying a shop.