Code P0171; P0174; and P1000


GTED

GT Owner
Apr 4, 2006
773
Hi

I've searched the forum and know what code p1000 is (readiness test), but does anyone know what P0171 and P0174 mean? Here is the situation, 2 weeks ago I had to "return to stock tune" as I needed to get the GT smogged, and as usual, I'd need to drive the car for ~50 miles for the ecu to re-learn the stock tune. Now 2 weeks and ~120 miles later, the readiness test isn't done yet, and I get the P0171 and P0174 codes, in addition to the P1000. For example, in the morning when I start the car, I'd only have the code P1000 on, then, I cleared the code, and drive the GT to my office and I'd read the code, and my SCT would show all 3 codes, then, at the end of the work day, I'd cleared the codes before I drive home, and when I get home, the 3 codes are on again..... However, all the while, the check engine light isn't on. I also know that the P1000 would not cause the check engine light to come on, but I guess neither do codes P0171 and P0174.

Has anyone had P0171 and P0174 codes before, and know what they mean? I'm wondering that the reason the readiness isn't "re-learned"..., could it be the fact that these 2 additional codes kept popping up, so the ecu would not finish the readiness test.

Advise please.

thx

GTED
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,558
Hi Ed,

P0171 and P174 are fault codes for being too lean (Bank 1 and Bank 2). Are you by chance running a MAFia and, if so, when you returned to the stock tune, did you disconnect the MAFia? Lean codes are fairly serious. Be careful as you diagnose this. I'm PM'g you me cell if you have time to chat I think we can find the casue pretty quickly...
 
Aug 25, 2006
4,436
Did you get the situation resolved?

The P1000 code will remain as long as the others are in place as the OBDII system cannot not successfully complete the component testing processes with no issues.

Takes care

Shadowman
 

GTED

GT Owner
Apr 4, 2006
773
Hi Kendall, thank you for our quick chat, and set me straight! Just got home, codes P0171/0174 no longer on; therefore, within the next 20 miles, the code P1000 should be done as well.

Hi Bill, thank you for checking up on me. Yes, with Kendall's advise earlier, I'm sure the readiness test will be reset soon, since the lean codes are now gone.

Great forum community!

Ed
 

twobjshelbys

GT Owner
Jul 26, 2010
4,965
Las Vegas, NV
Hi Kendall, thank you for our quick chat, and set me straight! Just got home, codes P0171/0174 no longer on; therefore, within the next 20 miles, the code P1000 should be done as well.

Hi Bill, thank you for checking up on me. Yes, with Kendall's advise earlier, I'm sure the readiness test will be reset soon, since the lean codes are now gone.

Great forum community!

Ed
What was the problem and fix? Inquiring minds want to know...
 

BlackICE

GT Owner
Nov 2, 2005
1,412
SF Bay Area in California
Probably as Kendall said, disconnect the Mafia.
 

GTED

GT Owner
Apr 4, 2006
773
Since I only return to stock every 2 years, I forgot one extra step to get the readiness test done, for those of us have mafia as part of our set up (mostly for the whippled GTs).... I forgot to bypass the wires that go in/out of the mafia; therefore, the mafia was continuing "fooling" the car's ecu, while already returned to stock....., hence the ecu detected/interpreted the engine was running lean.... Once Kendell reminded me of that, I did the bypass before I leave the office yesterday and when I got home, voila, codes 0171/0174 were gone, so now all I need is to drive the car for another few miles, the code P1000 should be gone soon as well. To prevent this momentary senior moment for 2 years from now, I did a note-to-self...:)

Ed
 

BlackICE

GT Owner
Nov 2, 2005
1,412
SF Bay Area in California
I had a similar brain fade during a smog test when I forgot to turn off traction control. The car kept miss firing when the engine was reved.
 

GTED

GT Owner
Apr 4, 2006
773
Success! The Readiness was completed last week, and I spent a total of 15 mins, this morning, at the smog station to get the bi-annual smog test done.

I have another question..... How do you suppose the GT would run, with a 91 octane tune for Whipple, but without re-connecting the MAFia? So, after the smog is done, but before even leaving their parking lot, I reloaded my mod tune back, and since my house is only ~3 miles away, I decided not reconnect the MAFia in front of the smog station. On the way home, the idling and street driving was fine, then, when I got on the fwy, I depressed the accelerator about 1/2 way down ( half wot..), as soon as the rev got to about 4k rpm, the engine would sputter. I did this twice on the fwy and same would happen. Of course, I backed off immediately each time.

When I got home, I reconnected the MAFia, and reloaded the same mod tune. Took the GT back on the fwy for a one exit run, with a couple of half-wot bursts. Everything was fine, the car pulled like mad, without any misses or sputter... Do you think the sputtering was attributable to the MAFia not being reconnected while running a mod tune?

Ed
 

BlackICE

GT Owner
Nov 2, 2005
1,412
SF Bay Area in California
Do you think the sputtering was attributable to the MAFia not being reconnected while running a mod tune?

Ed
Yes, never do that again!

The MAFia modifies that MAF output and the mod tune expect to see the changes. Your car was running rich during open loop.
 

GTED

GT Owner
Apr 4, 2006
773
Got it, thanks, Clinton! Good thing I backed off immediately.

Ed
 

BlackICE

GT Owner
Nov 2, 2005
1,412
SF Bay Area in California
Got it, thanks, Clinton! Good thing I backed off immediately.

Ed
Rich won't kill your engine, but could foul the plugs. The other way running a Whipple tune with the Mafia disconnected will kill the motor fast if you get on the boost as will running the stock tune with a Whipple without the Mafia and getting on the boost.
 

SMOKDU

GT Owner
Dec 17, 2011
397
Bigger mass air meter and I got rid of the mafia.