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Like it says in the title, throwing a few codes on an ’05 Tacoma 2.7.
P0300- Random miss
P0171- System Too Lean (Bank 1)
P0172- System Too Rich (Bank 1)
P0125- Insufficient Coolant Temp. for closed loop fuel controlThe only driveability problem I’ve felt is the misfire. I am also assuming that my P0125 is causing everything else. If the ECU doesn’t see the temp it needs to, it will cut/add fuel, thus causing the three other codes. I have access to a scantool and the truck runs at 176 degrees, which ALLDATA considers to be normal, although it is at the lower range of normal. I’m also part of a tacoma forum and one of the peeps gave me this bit of info:
“Interesting thing! I just went into Mitchell1 service information and actually looked up the Toyota diagnostics for what the failure conditions are, and what can cause this code to set. According to Toyota, the P0125:
‘DTC is set when sensor (Oxygen sensor) does not output a rich condition once engine is at normal operating temperature, engine speed of 1500 RPM or more, and vehicle speed is 25-62 MPH for at least 2 minutes.’
According to Toyota, the most probably cause for this code is a faulty oxygen sensor (the one in the front of the cat)
I admit this is very different from the diagnostics of other manufacturers, but this is direct from Toyota.”I will check my fuel trims and post them up in a little bit.
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+1 to the above post.
The PCM will try to attain a 14.7:1 stoichometric ratio once in closed loop (reading from the o2 sensor). Anytime the accelerator pedal is suddenly depressed, that ratio is lowered (12.1:1 example) and the vehicle will fall out of closed loop as it is not using the 02 sensor for stoichometric ratio’s at that one given time.
I get what you guys are saying, but the concern was when I let off the throttle. That’s when it would go into open loop. I didn’t snap throttle it at all. It was gradual as you can hear in the vid.
Thanks Eric, I’ll look into diagnosing the too lean/too rich codes hopefully tomorrow, because it’s been raining here in Cali. Both of those codes use the same flowchart, so if it ends up being the AFR sensor, I’ll probably find it. I’ll also look into the clutch. Thanks for the help everyone. Keep you guys posted!
I don’t think it slipping into open loop when you let off the gas is a bad thing. You may be reading a little too much into it. Remember the golden rule of KISS, Keep It Simple Stupid. Keep us posted.
[quote=”EricTheCarGuy” post=40928]I don’t think it slipping into open loop when you let off the gas is a bad thing. You may be reading a little too much into it. Remember the golden rule of KISS, Keep It Simple Stupid. Keep us posted.[/quote]
Hahaha, I’ll keep that in mind. I still have yet to find the problem, BUT my clutch is in good working order… On to more diagnosing…
This thread is extremely old lol… I still have yet to figure it out though, but these codes are no longer stored. Haven’t been for a while, yet I’m still feeling a random misfire. She runs a heck of a lot better when it’s cold outside, but so do a lot of cars haha. I also want to say that the misfire is a little more noticeable when it’s humid.
So this is what i’ve diagnosed in the past 3 years, lol. And I did end up replacing the t-stat with an oem one since I work for toyota and get parts for cheap (mwahaha).
Number 3 cylinder has about 15-20 psi drop in pressure compared to the rest and found that it was due to rings. The truck has about 178k miles on it.
I have also noticed (even before I swapped an OEM t-stat) that the radiator hose after the t-stat never gets hot, but is holding a butt load of pressure. The truck has never overheated on me. I also started getting traces of oil inside of my coolant reservoir which lead me to believe that I had a busted headgasket, so I did a leakdown and nothing came up. I also tried a block test, but that didn’t do anything because the t-stat never opens. Same with using the smog machine to test for HC’s in the cooling system. Wouldn’t read because the t-stat never opened… This truck is a headache and still runs okay, but the misfire drives me crazy. Any ideas? Thanks in advance!A random misfire can be fuel or spark related. It can also be a vacuum leak.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
I tested for vacuum leaks with some carb cleaner multiple times, but couldn’t find anything. I even got so frustrated one day and started spraying water in any vacuum related spots and found nothing… Since the truck is an ’05 the techstream can’t get live data on fuel pressure. I wish it could though… Do they make extensions for fuel pressure gauges so I can look at pressure while driving the vehicle? lol
Did you ever replace the AF sensor? Denso only…. Also, FWIW…Toyotas can throw a P0125 as a ghost code that comes from issues with the O2 sensor circuit… I would check the O2 heater relay and circuit…
check out this link
[quote=”hondaguy453″ post=147372]I tested for vacuum leaks with some carb cleaner multiple times, but couldn’t find anything. I even got so frustrated one day and started spraying water in any vacuum related spots and found nothing… Since the truck is an ’05 the techstream can’t get live data on fuel pressure. I wish it could though… Do they make extensions for fuel pressure gauges so I can look at pressure while driving the vehicle? lol[/quote]
No extensions but tape the gauge to the windshield and drive it to monitor the pressure.
I’ll test the fuel pressure and O2 so we have some current numbers going again. I didn’t even think of taping it to the windshield lol. I’ll do that!
[quote=”hondaguy453″ post=147472]I’ll test the fuel pressure and O2 so we have some current numbers going again. I didn’t even think of taping it to the windshield lol. I’ll do that![/quote]
🙂
I need to buy a better fuel pressure tester kit. I don’t have the attachment for the quick disconnect… I thought I did lol. I’ll ask my buddies. I tried to get under the truck to test the O2 but I wasn’t able to nor do I think I can get it disconnected. I’m actually on leave due to shoulder surgery that I got about a month ago, which is also why I spend so much time on here lol. I get bored at home doing nothing all day hahaha… Anyways, I’ll see if I can get someone to test them for me. I’ll just walk em through it. Keep you guys posted!
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