Fuel problem code light comes on, I find it is a lean mixture at Part load under the codes. No Problem with the car and we live in a hilly area with steep inclines. Been doing it for 2 years. Assume it could be fuel filter but again, no problems. I kill the code to pass inspection and it comes on again several days or even a week later.
Hi there:
DTC P1128 is "Long Term Fuel Trim Too Lean"
This means the air/fuel mixture is leaner than the HO2S can compensate for.
This is most often caused by a vacuum leak. It can also be caused by a clogged fuel filter, unmetered air entering the air intake system, leaking exhaust system, canister purge system not operating or a weak fuel pump.
Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.
Thank you for using FixYa, have a nice day.
SOURCE: check engine light is on
There are many causes to this problem, but you might need to take it to a shop to find the real problem.
Here's everything I know about it.
P0171 System too Lean (Bank 1)
How does a P0171 code trigger the check engine
light? This code will trigger the check engine light as follows:
The adaptive fuel strategy in the vehicle's computer constantly monitors the fuel delivery system to make sure the engine is running at an optimum air to fuel ratio, which is 14.7:1. The computer adjusts injector pulse width to regulate the amount of fuel going into the engine. The oxygen sensors relay information to the Powertrain Computer Module (computer), informing it of the oxygen content in the exhaust. This information is translated by the computer, and used to determine if more or less fuel is needed. The computer will then adjust fuel flow (and possibly other related engine operating characteristics), to keep the correct air fuel mixture. This loop continues as long as the engine is running.
A P0171 check engine light code is set when the computer has reached a rich calibration limit and can not add enough fuel to maintain the correct mixture.
Possible Causes:
Fuel System:
Leaking or faulty fuel pressure regulator
Plugged or dirty fuel filter or lines
Fuel pump weak or defective check valve
Injectors leaking or faulty
Low fuel pressure or running out of fuel
Leaking EVAP system components
Faulty FRP (Fuel Rail Pressure Sensor)
Air Intake System:
Vacuum leaks
Contaminated, damaged or faulty Mass Air Flow sensor
PCV valve leak or stuck open
Air induction turbulence caused by wrong filter
Oil dipstick not seated
Air leaks after the Mass Air Flow Sensor (MAF)
Oil coated aftermarket air filter
Exhaust System:
Any exhaust leak before or near the oxygen sensors
EGR System
Vacuum line disconnected from EGR System Module (ESM) EGR valve, tube or gasket leak
EGR vacuum regulator valve leaking
Secondary Air Injection System
Mechanically stuck secondary air injection valve
SOURCE: what does code number P1128 mean when light is on
P1128 - Long Term Fuel Trim Multiplicative System Too Lean.
The ECM
will set a code and the MIL will turn on if the long-term fuel trim
value goes from 10% to 15% lean for 30 seconds during two driving
cycles when the following conditions are met:
1.- Engine loads exceeds 1.8 milliseconds.
2.- Engine coolant temp. is above 158F (70C).
3.- Canister purge system is not operating.
4.- Mass air flow is less than or equal to 5.5grams per second.
5.- Engine speed is below 1000RPM.
Please Rate Me =]
SOURCE: p1128 code on 2000 hyuandai accent
I did some research because the P1128 is an odd code for Hyundai and I couldnt find a lot of information on it, but I found two things that may help and neither point to the fuel pump.
1. P1128 in Hyundai refers to the Mass Airflow Sensor or MAF being defective.
2. There is a TSB from Hyundai, TSB 01-36-022, but I wasnt able to ascertain if that was a specific TSB for the MAF or if it was information on how to test the MAF or some other information.
P1124 seems to be a related code as well but I could find little on it. P1124 in a Subaru is an issue with the Throttle Position Sensor or TPS, but I could not confirm that for Hyundai.
My first suggestion would be to check your air filter and if it has not been changed in a while or is really dirty, then change it as a restriction in air flow might be mistaken by the computer as a problem with the MAF.
SOURCE: 2001 Hyundai and I have the same code and problem
Firstly, these codes are set when the fuel 'TRIMS' are out of spec (either tool LEAN - P1123, OR too RICH - P1128).
The air/fuel control system, in addition to a number of sensors, includes the following components and systems:
a.
Intake air system.
b.
Exhaust system.
c.
Evaporative emissions control system (includes purge control solenoid valve).
d.
Fuel injectors.
e.
Fuel pressure regulator.
f.
Fuel pump.
For the air/fuel ratio to be within limits, all of the sensors, components and systems associated with the air/fuel control system must function within normal parameters.
STOP replacing parts/sensors unless you can VERIFY they are defective!
The Powertrain Control Module (PCM) on Hyundai OBD II vehicles (all 1996 and later models) can adjust the engine Air to Fuel (A/F) ratio to compensate for variations in operating conditions. This adjustment only takes place during "Closed Loop" operation.
The PCM uses input from the following components to determine the amount of fuel to deliver:
The ability to adjust the A/F ratio enables the PCM to compensate for engine, fuel and sensor variations as well as temperature, altitude and humidity. This enables the vehicle to maintain a stoichiometric (14.7 to 1) A/F ratio that will ensure optimal engine performance and minimal emissions.
Since the PCM can change the A/F ratio to compensate for a wide range of conditions, an indicator is needed to identify that a compensation has been made. Fuel Trim values shown on the HDS scan tool are the primary indicator that an adjustment in fuel delivery has taken place.
The scan tool displays the PCM's A/F ratio compensation as "Short Term" Fuel Trim (ST TRIM), Long Term Fuel Trim (LT TRIM), and "Oxygen Sensor" Trim (TRIM B1 S1 and B1 S2). The most beneficial diagnostic information comes from "Short Term" Fuel Trim and "Long Term" Fuel Trim.
AFTER ALL THIS, I think it's simply your Coolant Temperature Sensor giving 'FALSE' information to the engine control module/powertrain control module (ECM/PCM).
SOURCE: trouble code 1997 Hyundai Elantra, P1128
P1128 trouble code is for (Upstream Heated O2 Sensors Swapped). Did you switch around any of the O2 sensors?
WITH MANUAL TRANSMISSION
Table 3: Using the Hi-Scan Pro in the Hyundai Diagnostic
Menus Current Data Screen
TPS (%)
0
2.4
3.9
5.9
MAF (kg/h)
9.5
19.4
28.8
43
RPM
IDLE
2000
3000
4000
Table 4: Using the Hi-Scan Pro in the OBD-II Menus Current
Data Screen
TPS (%)
0
2.4
3.9
5.9
MAF (g/h)
2.5
5.5
8
12
RPM
IDLE
2000
3000
4000
2,948 views
Usually answered in minutes!
×