99 Taco v6 throwing codes... Leaning out?

74k5 · 01-30-05, 10:39 PM

My 99 TRD is throwing two codes PO171ALT fuel trim system lean and PO125 ECT Excessive time to closed loop fuel control. The second O2 sensor reads like it isnt working. The truck only has 50k on it and everything is connected underneath and all the wires look good (nothing torn out or frayed.)
I was curious if there was a way to check and see if the O2 sensor was functiuoning without removing it. I wouldnt be surprised if the prior owner hollowed out the cat, I think this would throw a similar code. Also is top end lean out a common problem with the taco V6 (3fzE?) Any help would be great. Thanks, Mike

calamaridog · 01-30-05, 11:37 PM

Mike, running lean is only a problem with the supercharger and no fuel mods. Check the plugs, clean the MAF, and run some SEAFOAM through the motor to clean out your carbon deposits. Pull the battery terminals and reset the ECU. Codes should go away... They did on my buddies Taco with the same problems, and we didn't have to change the O2 sensors.

nate · 01-31-05, 11:40 AM

The thing that made me think that it was a bad O2 sensor or the cat is punched out is the rear sensor is showing a 99% fuel trim.
My Jeep has a hollowed cat and it shows the same thing as well.

The O2 sensor seem to bounce around alot... 750Mhz, down to 50Mhz all in a few seconds.

I just got the scanner a little bit ago, so not completely familar with the readings.

Mike said he discoed the battery twice, and I came up with 3 codes... 2 PO171s and the PO125.. I did clear the codes with the scanner... though I'm sure they will pop back up in a short time.

calamaridog · 02-01-05, 02:12 AM

Well, I can't say as I have no experience with the cat thing. In CA, there are serious penalties for messing with the emissions systems so I don't go there. They take peoples cars for that sort of thing here.

I would figure out if the cat is modified 1st as that may explain a few things. Not sure how much an O2 sensor costs?

desertdude · 02-01-05, 07:38 AM

Depends on which 02 sensor. I have paid up to 300.00 for the one in the exhaust just down from the manifold.

nate · 02-01-05, 04:37 PM

Whoah that's expensive. Most I've seen are in the $50-70 range... I don't buy Toyota parts too often though.

desertdude · 02-01-05, 06:26 PM

yeah I chocked on it too. I installed it to save a few bucks. I had to change out all the sensors...:( That was my 2000 Tacoma. I traded up for an 04 Tacoma so far 31K and lovin it...

01-30-05, 10:39 PM	#1
74k5 IH8MUD Rookie Join Date: Nov 2004 Posts: 24	99 Taco v6 throwing codes... Leaning out? My 99 TRD is throwing two codes PO171ALT fuel trim system lean and PO125 ECT Excessive time to closed loop fuel control. The second O2 sensor reads like it isnt working. The truck only has 50k on it and everything is connected underneath and all the wires look good (nothing torn out or frayed.) I was curious if there was a way to check and see if the O2 sensor was functiuoning without removing it. I wouldnt be surprised if the prior owner hollowed out the cat, I think this would throw a similar code. Also is top end lean out a common problem with the taco V6 (3fzE?) Any help would be great. Thanks, Mike

01-30-05, 11:37 PM	#2
calamaridog IH8MUD Lifer Join Date: Jun 2003 Location: Cuyamaca, CA and Las Vegas, NV Posts: 2,572	Mike, running lean is only a problem with the supercharger and no fuel mods. Check the plugs, clean the MAF, and run some SEAFOAM through the motor to clean out your carbon deposits. Pull the battery terminals and reset the ECU. Codes should go away... They did on my buddies Taco with the same problems, and we didn't have to change the O2 sensors. __________________ 2000 UZJ100 - OME - sold Currently looking for the right FJ60 TLCA #14734 Calamaridog

02-01-05, 02:12 AM	#4
calamaridog IH8MUD Lifer Join Date: Jun 2003 Location: Cuyamaca, CA and Las Vegas, NV Posts: 2,572	Well, I can't say as I have no experience with the cat thing. In CA, there are serious penalties for messing with the emissions systems so I don't go there. They take peoples cars for that sort of thing here. I would figure out if the cat is modified 1st as that may explain a few things. Not sure how much an O2 sensor costs? __________________ 2000 UZJ100 - OME - sold Currently looking for the right FJ60 TLCA #14734 Calamaridog

02-01-05, 07:38 AM	#5
desertdude IH8MUD Lifer Join Date: Nov 2003 Location: Sedona Arizona TLCA# 2911 Posts: 2,813	Depends on which 02 sensor. I have paid up to 300.00 for the one in the exhaust just down from the manifold. __________________ <---------------------©-------------------> • North <-> South <-> East <-> West • <---------------------©------------------->

02-01-05, 06:26 PM	#7
desertdude IH8MUD Lifer Join Date: Nov 2003 Location: Sedona Arizona TLCA# 2911 Posts: 2,813	yeah I chocked on it too. I installed it to save a few bucks. I had to change out all the sensors...:( That was my 2000 Tacoma. I traded up for an 04 Tacoma so far 31K and lovin it... __________________ <---------------------©-------------------> • North <-> South <-> East <-> West • <---------------------©------------------->

01-31-05, 11:40 AM	#3
nate IH8MUD Rookie Join Date: Jan 2005 Posts: 52	The thing that made me think that it was a bad O2 sensor or the cat is punched out is the rear sensor is showing a 99% fuel trim. My Jeep has a hollowed cat and it shows the same thing as well. The O2 sensor seem to bounce around alot... 750Mhz, down to 50Mhz all in a few seconds. I just got the scanner a little bit ago, so not completely familar with the readings. Mike said he discoed the battery twice, and I came up with 3 codes... 2 PO171s and the PO125.. I did clear the codes with the scanner... though I'm sure they will pop back up in a short time.

02-01-05, 04:37 PM	#6
nate IH8MUD Rookie Join Date: Jan 2005 Posts: 52	Whoah that's expensive. Most I've seen are in the $50-70 range... I don't buy Toyota parts too often though.

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