Volkswagen P1128: Long Term Fuel Trim Add. Air. Bank 1 System Too Lean

Is your scanner showing Volkswagen P1128?
No worries. We'll show you what it means and how to deal with it.

Presented by
OBDCodex, Editor

Volkswagen P1128: Long Term Fuel Trim Add. Air. Bank 1 System Too Lean

DIY Difficulty Level
Repair Cost
Can I Still Drive?

What Does The Volkswagen P1128 Code Mean?

Engine started, battery voltage must be at least 11.5v, all electrical components must be off, the ground between the engine and the chassis must be well connected, the exhaust system must be properly sealed between the catalytic converter and the cylinder head, and the oxygen sensor heater for oxygen sensor before the catalytic converter must be properly functioning. The fuel mixture is so rich that the O2S control is on lean limit.

Note: When an O2S malfunction (P0131 to P0414) is also stored with this malfunction, the O2S malfunction(s) should be repaired first. Note: After exhaust system repairs, make sure exhaust system is not under stress and that it has sufficient clearance from the bodywork.

If necessary, loosen double clamps and align exhaust pipe so that sufficient clearance is maintained to the bodywork and support rings carry uniform loads. Do not use any silicone sealant. Traces of silicone components which are sucked into the engine are not burned there, and they damage the oxygen sensor.

What Are The Potential Causes Of The Volkswagen P1128 Code?

  • Fuel pressure is too low or fuel quantity supplied is too low
  • Fuel filter faulty
  • Transfer fuel pump has failed
  • Fuel injector is faulty (sticking or not opening)
  • Engine speed (RPM) sensor is faulty
  • MAF sensor circuit open
  • MAF sensor circuit shorted to ground
  • Air leak in the manifold
  • Secondary air injection system combi-valve stuck open
  • Secondary air injection system electrical short
  • ECM has failed

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> WORKPRO 582-piece Crimp Terminals, Wire Connectors, Heat Shrink Tube, Electrical Repair Kit
>>> Twippo 372Pcs Waterproof Wire Connectors Kit
>>> Duralast EGR Valve EGR4397
>>> Volkswagen Jetta Exhaust Gas Recirculation (EGR) Valve Gasket
>>> Volkswagen Vacuum Hose Parts
>>> Exhaust Manifold Gasket for Volkswagen Jetta

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

Volkswagen P1128, DTCDECODE.

Tagged :
You know someone would like this

Leave a comment

Your email address will not be published. Required fields are marked *