Hello all! I am new to this forum, i actually just created an account to try and figure out this problem! Im hoping you Land Cruiser experts can help me out. My wife has a 1995 Toyota Land Cruiser that has been throwing a P0170 (Fuel Trim Malfunction) code on and off for the past 6 months or so. I am an ASE certified mechanic out here in Cali so i do all of the work on our Cruiser myself. I have replaced the following trying to fix this issue: Upstream O2 sensor (Denso), NEW OEM MAF sensor, NEW Denso Fuel pump and NEW fuel filter. Fuel pressure is about 40 psi at idle. Fuel pressure regulator seems ok. Injectors were removed and cleaned when i swapped the engine about 6,000 miles ago. NO vacuum leaks (i smoke tested it at my shop) and fuel trims at idle seem ok... 0.0 at idle and no more than +9% under load. I am at a total loss now trying to fix this issue as it just threw the code again today after being ok for the past 3 months after i replaced the fuel pump... Please HELP! Thanks Guys!
P0170 Code!
- Thread starter Chunky95
- Start date
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I assume you have access to a Toyota Factory Service Manual, right? If so, have you done any of the tests that the FSM says might be the problem?
- Thread starter
- #3
Yes, I have access to ALLDATA and all service info. I have performed all tests related to the fuel system as specified in the FSM and everything seems to check out... TPS within spec, MAF, Fuel pressure, also, I have a Snap On Solus Ultra scanner at home and i just did a data log session while driving and the Fuel trim never went above +9%
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- #4
The strange thing is, The Toyota FSM says the P0170 code for the 1995 LC is not set until fuel trims have reached +/- %35 and my trims are not even close to that... leads me to believe a sensor is failing somewhere and the signal is intermittently dropping out and setting the code, then when i go to data log a drive session, the sensor is ok and all values return back to their specified range...
It doesn't show P0170 but does show P0171 and P0172. Dont know if this will help or not.
Have you removed the large intake hose between the air cleaner and throttle? Looks for cracks in the ribbed area and cracks or hardening of the hose at the throttle.
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- #6
Thanks landtoy80! i really appreciate the help. I replaced the air intake hose last year due to a large crack near the throttle body. It was replaced with a new OEM dealer part. And since my LC is a 1995, that transition year between OBD 1 and OBD 2, unfortunately my ECM does not set a lean or rich code, just the P0170 Fuel trim malfunction... the pics u posted mentioned the coolant temp sensor as a possible problem, im going to look a little more into that tomorrow at work. Thanks again! I cleared the code tonight, im going to let the wife drive it and see how long/how many miles it stays off.
Have you looked at the PCV valve? Is it OEM and has it been replaced lately (not cleaned). Read that some cheap aftermarket PCV valves that allow too much airflow (vacuum loss) and cause a lean condition, then the ECU adds more fuel to compensate.
Its a long shot on this one but I see you are not using all OEM parts. Have read here that non-OEM O2 sensors have had issues.
When my 94 gets code 25 26 rich lean condition its from dirty or fouled O2 sensors. My motor uses a bit of oil and the oil that has more ZDDP in it than gasoline motor oils (I use Rotella T6 oil for commercial diesel trucks) and that ZDDP coats the O2 and triggers the rich lean code. What is strange is, if I drive all hwy miles, the codes go away. If I drive city miles, the codes will come back.
Its a long shot on this one but I see you are not using all OEM parts. Have read here that non-OEM O2 sensors have had issues.
When my 94 gets code 25 26 rich lean condition its from dirty or fouled O2 sensors. My motor uses a bit of oil and the oil that has more ZDDP in it than gasoline motor oils (I use Rotella T6 oil for commercial diesel trucks) and that ZDDP coats the O2 and triggers the rich lean code. What is strange is, if I drive all hwy miles, the codes go away. If I drive city miles, the codes will come back.
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- Thread starter
- #8
I replaced the PCV valve about 6months ago when this problem 1st occurred. Sorry i forgot to mention that. Also, i warrantied the 1st Denso O2 sensor that I installed just to rule out a defective part, this is the 2nd, new Denso O2 sensor that has been installed and the problem keeps coming back. I have also swapped the MAF from a friends LC and code came back with his MAF as well... When the code comes back, im going to install a new coolant temp sensor and see what happens. Thanks again for all your help!
How many miles on the 80 and does it use oil?
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The New engine has only about 8,000 miles on it. Only uses about 1qt of oil every 5,000 miles. The previous, original engine, had 250,000 miles before the #1 cylinder piston rings let go and began to burn oil, about 1 qt every 3 weeks and fouled spark plugs about once a week. The new engine was rebuilt here at my shop using all OEM toyota parts and gaskets. I built it from a bare block. Its been a great truck, we bought it with about 100,000 miles and only changed the radiator until the engine let go.
TrickyT
Hate that mud...
I think P0170 is unique to 1995 model year only. At any rate, if you plug in "P0170" in the search box at the top of this page you'll find a number of threads started by 1995 owners. Perhaps some of those will provide ideas to help you troubleshoot.
A 95 FSM would be a help too.
I've had the connectors at the MAF get fatigued and present a bad connection. The harness is supposed to be supported by a clip on the firewall side of the housing. If that has failed and the wire is hanging on by the connector I'd look there.
Pull out each pin one at a time and and bend the small leaf spring tab to increase the tension. Then support the harness to take the strain off of it.
Pull out each pin one at a time and and bend the small leaf spring tab to increase the tension. Then support the harness to take the strain off of it.
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- #14
I have access to ALLDATA which is very similar to factory service manuals. And I will try what you suggested landtank! Thank you!
Have you looked at the O2 plugs for corrosion?
Any results on this problem? I just got the same code this week.
Chunky, did you ever get this sorted out and if so, wht was the solution? Thanks
So, what was the end result? What triggered the P0170 CEL?
