P1128moderate severityPowertrain
Long Term Fuel Trim System Too Lean Bank 1
on 1998 Audi A8 4.2L V8 · AWD
What this code means
The ECU detected that the long-term fuel trim for Bank 1 has reached the maximum lean correction limit. The engine is not receiving enough fuel relative to the air charge, and the system cannot add more fuel.
Symptoms
- Check Engine Light
- Rough idle
- Hesitation on acceleration
- Lean misfire
- Poor fuel economy
Common causes
- Vacuum leak on intake side
- Weak fuel pump
- Clogged fuel injectors
- MAF sensor under-reading
- Intake manifold gasket leak
Diagnostic steps
- Perform smoke test for vacuum leaks
- Monitor fuel trim values
- Test fuel pressure
- Clean or test MAF sensor
- Inspect intake manifold gasket
Repair notes
Repair vacuum leaks first; then address fuel delivery issues if trims remain lean.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1