Hello Everyone.

I have a 2004 Mazda 6 V6, my CEL is giving me P0171, I've even had a P0301. Smells like it's running rich.

Tonight I went to Autozone and rented a scanner that gives me live data.

STFT B1 and STFT B2 stayed at 0 even when at 3k RPM.
LTFT B1 and LTFT B2 stayed at 20.3
Ideal RPM 738-755
MAF (lb/min) 0.5
FuelSys 1 OL-Fault
FuelSys 2 OL-Fault
Calc Load 18.0

Anything look off?

I forgot to get the O2 sensors results, however the scanner had a test for the O2 sensors and they passed.

I did clean the MAF and checked for vac leaks using carb cleaner. No see or here any.

Any idea where I should look?

 

If LTFT are both the same and recording positive 20, thats a massive amount of extra fuel the PCM is adding to try and maintain correct fuel trim. Anything over 10 is a red flag.

Positive fuel trim shows the engine is running lean and the PCM is adding fuel to richen things up a bit.

When you say the 02 sensors passed, what is the test carried out?

Can you monitor live data?

If one or both downstream O2 sensors are giving false data, telling the PCM that things are lean, when they are not, it would explain the high LTFT. Or there could be a massive air leak/ vacuum leak allowing unmetered air into the system.

P0301 is cylinder 1 misfire, it may be a faulty / dead injector.

 

DTC P0171 Fuel trim system too lean

DETECTION CONDITION

• The PCM monitors short term fuel trim (SHRTFT) and long term fuel trim (LONGFT) values during closed loop fuel control. If the fuel trim exceeds the preprogrammed criteria, the PCM determines that the fuel system is too lean.
Diagnostic support note
• This is a continuous monitor. (FUEL SYSTEM)

• The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

• The PENDING CODE is available if PCM detects the above malfunction conditions during the first drive cycle.

• The FREEZE FRAME DATA is available.

• The DTC is stored in the PCM memory.

POSSIBLE CAUSE

• Misfire

• Front HO2S deterioration

• Front HO2S heater malfunction

• Pressure regulator malfunction

• Fuel pump malfunction

• Fuel filter clogged or restricted

• Fuel leakage on the fuel line from the fuel delivery pipe and fuel pump

• Fuel return hose clogged

• Leakage in the exhaust system

• Purge solenoid valve malfunction

• The purge solenoid hoses are improperly connected

• Insufficient compression