I have a 2002 montero sport which has given me 2 engine code . I need to know what they mean? The first engine code is PO 174 The 2ard code is PO 154

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3.5L Engine Firing order: 1-2-3-4-5-6 Distributorless ignition system.

Mitsubishi Montero, Sport 1998-06 Firing Orders Repair Guide

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https://www.google.com/search?q=2002+Mitsubishi+Montero+Sport+3.5+firing+order

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MR988905 costs $300+

SNG O2 sensor is just below $100

they may claim being made with the same quality and both are tagged "direct fit" for easy installation.

its just my idea, good luck.

you can get guide from many sites.. i know few
like reliable-store
error codes/ fault codes, wiring diagrams, schematic diagrams, torque specs, engine info, switches functioning, assemble, disassembly, complete refurbish, repair, installation every single thing is covered
within seconds u can get the access and it's totally illustrative complete

If transmission fluid level is up to par then you just might need tranny repair. And that is not cheap.

Sounds like the oil level in the gearbox is low ,if it has a dipstick then start engine and chock wheels ,put in reverse with engine running and check oil level

PO 134 = 02 SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK 1 SENSOR1)
PO 153 =02 SENSOR CIRCUIT SLOW RESPONSE (BANK 2 SENSOR 1)
PO 154 =02 SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK 2 SENSOR 1)
PO 155= 02 SENSOR HEATER CIRCUIT MALFUNCTION (BANK 2 SENSOR 1)
PO 171= SYSTEM TOO LEAN (BANK 1)
PO 174= SYSTEM TOO LEAN (BANK 2)
I WOULD SAY YOU HAVE FAULTY OXYGEN SENSORS CAUSING THE ENGINE TO RUN TOO LEAN REPLACE THEM AND YOU SHOULD BE BACK IN BUISNESS

you need to change all the o2 sensors reset the computer it might come back on a couple of times just keep resetting it you could buy one of the cheap code scanners for 49 or 59 dollars and reset yourself if you go to a shop they are going to sell you a catalytic converter for a few hundred bucks and the code will come back. let me guess you got about 100,000 miles on it what it really means is a shop or dealer will get paid for a cat job when you dont need one

replace the o2 sensor the one before the cat converter with a quailty sensor like a denso brand o2 sensor

its an egr CIRCUIT MALFUNCTION which means can be any type of problem with the whole circuit -- wiring --connections fuses relays etc not just the egr valve more than likely the valve was good need to check and test the whole egr system

does it run differently?...have codes checked ...free at most good auto parts or trans shops now.... go from there