iamkeir

Hey folks,

I have a GT 2006 4.6L V8 which is currently throwing P0171 and P0174 error codes meaning system too lean on banks 1 and 2. It also failed its MOT on emissions (CO2, I believe) despite passing fine last year.

The LTFT 1 & 2 are maxing out at 25% under throttle load which is throwing the errors but all my other data/diagnostics seem fine and indicate things are running well. The car *seems* to be driving relatively well other than those codes, too.

I am investigating with the usual suspects (MAF, Lamdha/O2 sensors, fuel system, vacuum leaks, etc.) but I had a theory that I wanted to ask about…

It had some mods when I purchased it - BBK induction kit, long tube exhaust headers and magnaflow performance exhausts… and a custom remap/tune to go along with the mods.

However, I recently had some really extensive work done on the gearbox and I’m wondering if it might have ‘lost’ its custom tune during the work… and this could be causing the errors. If it has gone back to the stock tune despite having a bunch of mods (especially the cold air intake) could it be mismanaging the fuel/air?

I also wondered if it had be partially/fully decatted but an inspection from the garage suggests it still has cats intact and there are OBD values for cats present - plus it passed the MOT last year which surely would have been tough without them.

I’ve pulled off some of the data from the car and posted them here if useful.

I should add that I don't have the tune - no SCT Tuner was supplied... I am not sure if I could check whether it has a custom tune loaded or not?

So I have two main questions:

1) Could these errors be caused by mods/lost tune?
2) Which OBD values are failing the MOT on emissions?

Thanks for any insight/help, I really appreciated it

howarmat

if you lost the tune that would be a good place to start BUT its unlikely this happened. You can always clear the codes and load the tune again.

You are in a pickle without the tuner though. Both of those are common errors with exhaust modifications like you have.

iamkeir

Heh, I love that you used 'pickle'

Yeah, I imagine to go down this route, I'll need to get a new tuner and a new tune to suit mods?

danzcool

Given the large number of items in your images than have CMPL with a reading of NO, I'd say the sensor readiness tests have not completed...

drive cycle procedure:
...for all other Ford Vehicles
Pre-Conditioning Requirements:
· Cold soak the vehicle for 8 hours
· No DTCs present (clear all codes)
· Fuel fill between 15% & 85 %
Driving Procedure
1) Start the vehicle and idle for four (4) minutes.
2) Idle the vehicle in drive for 40 seconds (neutral for M/T).
3) Accelerate to 45 mph, using ¼ to ½ throttle (M/T stay in second gear for at least 5 seconds). Accelerate for at least 10 seconds and shift through to 5th gear.
4) Drive with a steady throttle at 45 mph for 30 seconds.
5) Stop the vehicle and idle in drive or neutral for 40 seconds.
6) Drive at speeds between 25 and 45 mph for 15 minutes.
Use ¼ to ½ throttle accelerations. Include the following conditions:
· At least 5 stops with ten seconds of idle time.
· At least 3 steady speed sections of 1 ½ minutes duration.
7) Drive the vehicle between 45 and 60 mph for 8 minutes (use high gear).
8) Maintain a steady speed between 45 and 60 mph for 5 minutes.
9) Drive the vehicle between 45 and 60 mph for 8 minutes (use high gear).
10) Stop vehicle, idle for 40 seconds.

iamkeir

I managed to get my hands on an SCT Tuner and realised the tune was set to stock CAI and exhaust. Set them to BBK Induction and Long tube headers, turned off rear O2 sensors, and the engine light has gone! So sounds like the tune had been removed/reset...

howarmat

glad its worked out