2G 2G Fault Code: P0170 Fuel Trim Malfunction

[BIGGSIE]

OK before everyone tells me to search, I have. I've also found a scanned page from a service manual and I have a Chilton's manual. I am an experienced tech and I know what I'm doing (so I thought.) Anyway the list of causes for this P0170 Fuel trim malfunction DTC is:

MAF sensor - Tested ok replaced with a spare one, DTC came back.
Injector - Tested OK replaced all 4, DTC came back.
Intake leak - Pressure tested to find one VERY small leak at TB shaft
have not replaced o-rings yet but I don't think that's it.
Fuel PSI - OK 41 psi base
Coolant temp sensor - OK shows 199* when needle is straight up.
Intake air temp sensor - OK shows 45* on a 35* day.
Baro sensor - OK shows 13.9 (normal)
Exh. manifold cracks - None found.
02 Sensor - Damn Snap-on scanner reads very slow, might be the problem but I would expect a 02 code.

As soon as the CEL comes on the car hesitates on hard acceleration, under boost. Does anyone have access to a "flow chart" for this code? Or any input on what fixed your's?
Sorry for this long post but this CEL is getting on my nerves.

 

[Doug99RS]

What about turbo to exhaust manifold gasket, turbo to O2 housing gasket? Also did you check to see if the upstream O2 is tight? If it sucks in air then it could increase O2 levels.

Do you know if P0170 is: Fuel system lean, rich, O2 slow to change, O2 shorted to voltage, or anything specific to the nature in which the fuel trim is behaving?

I've looked in my diagnostic book here but P0170 is not listed. Every code around it is there like P0171 Fuel system lean, and P0172 Fuel system rich.

I think it may be a Mitsubishi code and I'm looking in the Chrysler book (normally works for both, guess I found my first exception).
Doug

 

[4x4 tsi]

I have the same problem bro...I really want an answer also so BUMP.

Keep me posted please.

 

[BIGGSIE]

On the Snap-On scanner all it says is P0170-fuel trim malfunction. I would assume it's rich because my gas mileage sucks but the scanner does not specify. If I read the trims to you would that help?

 

[rice_rocket]

I've had this problem twice.. and it was the weirdest fix, no guarantees in yours.

First time: Exhaust leak. Not your regular leak, downpipe rubbed on a piece of metal, small hole in it. Would have never noticed it, but took it off to look at turbo.

Second time: Metal clip on one of my injectors fell off. Only on hard boost the plug would flutter a bit and get loose, then go back on. Fixed that clip, all is good. At an idle or stand still everything worked fine.

Just go try those things, easy and quick, it might solve your problem.

 

[jimh]

I believe this code is thrown when the ECU can no longer adjust the fuel trims to where it wants them. For my 2g, the STFT and LTFT together were greater than -30% which is the ECU's limit and caused it to throw the code.

 

[Doug99RS]

I believe that's the case as well.

Scenario 1: Engine is running too lean
-O2 reads high oxygen levels
-adds fuel to compensate
-O2 still reads too low
-adds more fuel and so on
-finally fuel trims are adding so much it falls out of the desired levels
-results in fuel trim code

Scenario 2: Engine running too rich
-O2 reads low oxygen levels
-reduces fuel
-O2 still reads too low
-reduces fuel again and so on
-Fuel trims read too low and falls out of desired ranges
-results in the fuel trim code.

If you can monitor the fuel trim readings and determine which direction the adaptive memories (fuel trims) have gone you can determine what the engine is doing or what the computer THINKS the engine is doing.
Doug

 

[luv2rallye]

If this helps any:

I have the '99 Mitsubishi manuals and it says jimh and Doug99rs are right.

(BTW it shows P0171 & P0172 are for the 2.0 N/T 420A while P0170 is for the 2.0 4G63 turbo and 2.4 4G64).

From page 13A-38 in the manual for troubleshooting code P0170: "If a malfunction occurs in the fuel system, the fuel compensation value becomes too large or too small. The ECM checks whether the fuel compensation value is within a specified range. Judgement critera: Long (short) range fuel correction has continued to be not lower than +12.5% (+10.0%) or not higher than -12.5% (-10.0%) for 10 sec."

It then has a long flow chart based on SCAN TOOL Data list values to isolate the problem.

 

[white 2g awd]

I had this code, and bad gas mileage, replacing the front O2 sensor fixed it. Also, if you have a data logger, try seeing if you are getting any readings from either of them, if not, there ya go.

oh yea, that's the only code I ever got for my O2 sensor.

Dustin

 

[Doug99RS]

Originally posted by luv2rallye


(BTW it shows P0171 & P0172 are for the 2.0 N/T 420A while P0170 is for the 2.0 4G63 turbo and 2.4 4G64).

That's what I was thinking. The book I have is the 97 Powertrain diagnostics manual for all of the FWD Chryslers (including Talon and Sebring coupe) but as I'm now finding out the Turbo car is definitely not covered. I'll have to see if I can liberate a Mitsubishi service manual from somewhere. Thanks for the input luv2rallye

 

[2GeNTSi]

I really need to figure out what is wrong as well, I've seen the code once on my datalogger. It happened out of nowhere while I was driving back from school, it was pretty hot out if that has anything to do with it. It was driving perfectly fine, my gas mileage is still really good I can get about 25mpg. I just went ahead and cleared it with my logger, then I received another CEL today coming from work today. I just got home like 10min ago so it is too late for me to be messing with my car, especially outside so tomorrow I will check if it is the same error.

 

[69_luv]

Damn these DSM cars. Once you get one thing fixed another pops up. I have the same P0170 Code on my palm.

I just replaced my upper O2, still no fix.
The car chokes really hard after 4500rpms. I can milk it up to 7k but its not happy about it. Palm says I am running good, .87 to .99 on the O2volt. I am going to go check all my flanges on the exhaust side, and also do a more intense boost leak check.

If anyone else comes up with fixes for this prob keep them posting.
Thanks

 

[SpeedFreak03]

P0170 Fuel Trim Bank 1

 

[swarm]

Anyone find a fix?

 

[Superman_gs]

I'm non turbo and same problem.

 

[Fullthrottle7]

I have recently had the same problem outlined above, but my car only seems to hesitate when my fuel level is below 1/4 tank.

The car hits complete fuel cut at about 4500-5200 rpms and the problem seems to happen most often after a complete stop followed by a right turn. A friend thought that there might be something wrong with the fuel pick up inside the gas tank, but after clearing the code, it comes back on within an hour or so even without the problem coming up again.

Does anyone have more information about this problem yet? Also, if it helps, my gas mileage seems to be pretty bad, about 18 mpg average even with easy driving. BTW, this is in a 95 TSi.

 

[prof]

I just encountered the P0170 code on my 97 GST. I replaced the front (bank 1) O2 sensor and cleared the code. I drove the car about 5 mile, street and highway, and the light is still off. I can't be sure just yet but it looks like the problem is fixed.

DAve

 

[damanca2828]

My car is a 95 TSI with K&N filter and BCS Restriction Removed

I first had the code pop up on me on the highway and didnt think much of it. Had it checked out and sure enough it was P0170 and the O2 sensors were reading funny, Snap-On code reader, so I replaced both, cleared the code and everything was good for a while.

Then it came back. So I went all out and had a new fuel pump put in, all new fuel filters, new plugs and wires, it was time anyways going on 80,000, and i noticed there was a manifold leak. Fixed it all and the code keeps coming back.

Im putting a downpipe and catback system on it soon. From the looks of it, it has to do with the exhaust, but what was weird was it was both O2 sensors not just one even after I fixed the manifold leak.

Sorry if this doesn't help anyone but after I get the exhaust I'll let everyone know if it fixed the problem.

 

[Doug99RS]

What exactly is a BCS restriction removal mod???

 

[swarm]

Inside the BCS (boost control solenoid) there are 2 outlets, one of them has a piece of round plastic inside that makes the diameter a bit smaller than the other one. supposedly removing that little sleeve allows your car to boost a few more psi.

 

[Doug99RS]

OK, that's good to know. I was concerned it was another "tamper with your BISS" type mod which I tend to frown upon.

 

[ASHICK]

The MDP sensor or MAP could give same p code 100 bucks dealer aftermarket too much

 

[envybianchi]

Oh man I really need some help! I have 2 trouble codes and I'm troubled! The 1st is PO170 & the 2nd is PO125. Please help me!!!!

 

[loweperf]

Correct me if I'm wrong (don't have access to specs at home) but aren't 2g fuel pressure specs 43-44psi. At the shop I've had Fords set fuel trim codes for fuel pressures 2-3 pounds down.

OBD II would definitely set slow response codes if the O2 was slow and usually an exhaust leak will set a no switch code. When you checked for leaks did you pinch the PCV line off?

Just a couple ideas. That smoke machine would come in handy right now!

 

[droptopgst]

Had that code with about 20 mpg. replaced the front 02 and now I am getting 26-29mpg with no more code.