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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 6957
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I have a Montero Limited 3.5L 6cyl. For the past couple of

Customer Question

I have a Montero Limited 3.5L 6cyl. For the past couple of months, I've been battling a p0170 & p0173. Before both those codes came up together, I had a p0125 & p0170 together. A mechanic changed the thermostat and the p0125 did not go away. The p0125 code once I swapped out my passenger side O2 sensor and the 2 post-cat O2 sensors. After I swapped those out, the codes that came back are the p0170 & p0173. Since then I've been chasing the problem. Do you have any idea what the problem could be?
Submitted: 11 months ago.
Category: Mitsubishi
Expert:  Doug replied 11 months ago.


What year is this Montero? There is a software update for erroneous P0125 that may apply. Likewise, has the fuel pressure been checked cranking/running/and key off to make sure there is no fuel pressure regulator issue (very common for P017x codes)? How about vacuum leak checks?

Customer: replied 11 months ago.
The Montero is 2001. I went to the dealer to get that software update but they told me that I didn't need it.I haven't checked out the fuel pressure because my STFT and LTFT only maxes out while in idle so I assumed that was a vacuum leak. Am I wrong in this assumption?
Expert:  Doug replied 11 months ago.

That's good if you have the software update already, so that rules that out anyway.

You could still go either way with the fuel trims.. in fact being at idle is less reliable in general than while driving anyway (often even zeroing out in some cases). Under load is when you get a most reliable reading.

With the engine running, if you spray brake parts cleaner around the intake manifold sealing areas does the engine flare/react at all?

Customer: replied 11 months ago.
Last week I just had these replaced:2 Intake Gaskets
Intake plenum gasket upper & lower
1 Throttle body gasketI replaced the EGR valve myself because I was told the diaphragm had a leak.Once I swapped out the EGR valve, the p0125 came back but I cleared it and it hasn't come back since.
The p0170 & p0173 came back after 20 or so miles.I'm wondering if the p0125 could set off the 170 & 173 and if so, how would I go about fixing that?
Customer: replied 11 months ago.
If the codes are being set for both banks, what can that tell me about the condition of my engine?