2001 hyundai accent, 1.4, manual trans. I have a code reader and I keep getting p1128 If I erase it the car runs sluggish, once the code comes on the car runs great. Is this a problem, or should I just run it?

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.


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No such code listed (P1128) for 2002 Accent

Go to www.hmaservice.com and register your vehicle by VIN #..
you'll then have access to wiring diagrams, shop manuals,
service bulletins, illustrations, etc. To diagnose a 2000 or 2001 1.5L Accent Diagnostic Trouble Code (DTC) P1128 (FUEL SYSTEM LEAN -- PART LOAD), check the following:

• Check the intake system for air leaks.
• Check that the Mass Air Flow (MAF) Sensor (P/N 28164-22610) operation meets the specifications listed below. If the MAF sensor output is significantly lower than the reference value (10% or more), then replace the MAF sensor.

Table 1: Using the Hi-Scan Pro in the Hyundai Diagnostic Menus Current Data Screen TPS (%) 0
3.5
5.1
7.4
MAF (kg/h) 10
21
30
47
RPM IDLE
2000
3000
4000
Table 2: Using the Hi-Scan Pro in the OBD-II Menus Current Data Screen TPS (%) 0
3.5
5.1
7.4
MAF (g/h) 2.8
6
8.5
12.7
RPM IDLE
2000
3000
4000

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

there is a power to the 16th terminal which scanners use for power, check the fueses and you will most likley see one if blown

P1128 is a lean condition, try cleaning the Mass Air Flow (MAF) sensor. You can buy a can of MAF cleaner at most auto parts store like Auto Zone, and they will have the instructions for you to remove the MAF. Try cleaning it first and then disconnect the battery, just make sure the radio is off first before you disconnect the battery. If the DTC 1128 is still there, the MAF may be bad and needs to be replaced but before you replace the MAF. Check with the Hyundai dealer for any TSB on that code. Good luck and keep me posted. The dealer want $270.00 for the MAF sensor!! ouch!! scouted around...NAPA has them for $105.00. Most local salvage yard for $35.00 - $75.00

probaly a reinder from hyundai that your engine needs servicing- oil change, fluid change, brake check, coolant check, etc. take it to a certified hyundai service facility and have them check it out! make sure you take your credit card, cash, or check-book!
Good luck! and be smart!

dear friend-looking at the fault code it tells me that your vehicle is running lean.plse look at the following:HO2S,FEUL PRESSURE,FEUL SYSTEM,MECHANICAL FAULT,ECM.

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.

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The trouble code P1128 is for a faulty mass air flow sensor or MAP. This is a common problem with 1999-2000 Accents. There is air leakage within the unit and/or the hot wire in the unit is badly contaminated. A bad MAP will cause the vehicle to bog and loose power.

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.