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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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You may have a bad fan clutch which is always engaged it should not be engaged at high speeds or when initially started up when cold.
I live in so. cal, so it’s usually 70 during the day and 50+ at night. Somewhere around there. So here are the pics of my t-stat.
The thermostat does not look bad.But looks can be deceiving.
did you test the t-stat in boiling water?Should the thermostat even open with the boiling water? ALLDATA says the temp should be between 176-183.
boiling water is 212F the t-stat temp is 180F +or –
at 212F that t-stat should be wide open. did you use
a thermometer to see the opening and closing points?Gotcha, I dunno why, but I was thinking Celsius lol. I found a digital thermometer, but the range wasn’t large enough… I can only say that it opened once it started to boil.
to be accurate you need a thermometer. to be even more
scientific/accurate.with the t-stat cold. place a small
thread string caught in the valve of the t-stat. immerse
fully in water.heat water while stirring. when the thermostat
falls from the thread. this is the valves opening point.continue
heating.check the full opening lift temp.aprox 203F.shut off heat and watch
the closing off temperature. science gotta love it.:)Haha nice! I’ll prob have to do it tomorrow so I can buy more coolant lol. Toyota coolant is expensive…
while we are at this.check the fan clutch.
http://www.hotrodders.com/forum/how-test-fan-clutch-141125.html
Reading through I don’t think the thermostat is the issue and I think you’ve proved it out. As pointed out if it’s not coming up to temp that would indicate that it would be stuck open but it’s not, or at least it doesn’t appear to be. I think you’re on the right track with looking for an issue with temperature. Based on your codes if it’s not going into closed loop it could cause that. Something also struck me is that you have a rich AND a lean code for the same bank. Given that the diagnosis called for replacement of the O2 perhaps that’s where you should start looking. It MIGHT be a fan issue but the evidence seems to support an O2 sensor problem.
I raised my RPM to 2100+, let go of the pedal, and it went into open loop for a split second.
whenever you gun the engine, it’s supposed to go into open loop.. the computer doesn’t care about fuel economy and stochiometric fuel/air mixture when you’re trying to pass grandma on the expressway. the computer basically says f** it and dumps raw fuel into the engine.
I raised my RPM to 2100+, let go of the pedal, and it went into open loop for a split second.
whenever you gun the engine, it’s supposed to go into open loop.. the computer doesn’t care about fuel economy and stochiometric fuel/air mixture when you’re trying to pass grandma on the expressway. the computer basically says f** it and dumps raw fuel into the engine.
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