P1128

P1128
Fuel Trim System too lean TRA (cylinder 1 - 3)
Oxygen Sensing Adaptation TRA (cylinder 1 - 3) Enrichment limit

Function
The adaptive oxygen sensing corrects longer lasting deviations of the fuel/air mixture of Lambda = 1 through changes of the calculated monitoring within the Engine Control Module (ECM) and with that the injection time. Should the correction factor through adaptation exceed a predetermined value, the diagnosis will detect the adaptation limit

Diagnosis condition
- Oxygen sensing system active.
- Time elapsed after engine start-up 250 to 350 sec.
- Air mass > 50 kg/h

NOTE: If TDC P1128 (Oxygen sensing at enrichment limit) is in memory, the fuel/air mixture is too lean. Always read the DTC memory as it is possible that there are other faults stored in memory which may lead the control to run against the limit.





Diagnosis Procedure
Connect scan tool and advance to menu point "DTC memory"
1. Connect scan tool with adapter cable.
2. Switch ignition on.
3. Start diagnosis and advance to menu point "DTC memory"
4. Read DTC memory.

- If other DTCs are in memory: Read DTC memory, correct faults
- If DTC P1128: Check air intake for leaks

Read DTC memory, correct faults
1. Read DTC memory.
2. Correct faults as per Diagnostic Trouble Code Charts (DTC).
3. Erase DTC memory.
4. Then road test vehicle to enable the system to monitor all components once.
5. Again read DTC memory.

- If no fault found: End
- If DTC P1128: Check air intake for leaks

Check air intake for leaks
1. Remove air cleaner and Mass Air Volume Sensor.
2. Using M 4 x 40 screws, attach sealing plate 9264/1 to hot wire air mass sensor.
3. With air pressure, build up 0.5 bar pressure.

- IF no pressure in air intake system: Find leak and correct.
- End





Check fuel pressure
1. Remove valve cover at test connection of fuel distributor line.

CAUTION: Cap must be used only once!

2. Connect pressure gauge P 378 or VW 1343 with attachment line 9559 and connect to test connection.





3. Remove ECM relay (R53) from fuse/relay panel and connect terminals 30 and 87b with locally manufactured fused jumper cable. Fuel pump must work now.

Fuel pressure:
Engine not running: 3.8 +/- 0.2 bar
Engine at idle: 3.3 +/- 0.2 bar.

Check fuel volume supply
1. Remove fuel return line at fuel pressure regulator.
2. Connect hose 9507 to connector for fuel return line at fuel pressure regulator. Hold connector hose in fuel receptacle.





3. Disconnect ECM relay (R53) from fuse/relay panel and connect terminals 30 and 87b with locally manufactured fused jumper cable. Fuel pump must work now.
4. Check fuel volume supply, Fuel Pump

- If the fuel volume is too low, check fuel circuit (pump, filter, etc.).

Fuel injectors contaminated (carbonized)
1. If check points 3, 4 and 5 are negative, the fuel injectors may be contaminated (carbonized).
2. Clean fuel injectors (ultra sound cleaning device) or replace.