P1133 Bank 1 Fuel Control Shifted Lean
What does P1133 mean on a Ford?
P1133 — Bank 1 Fuel Control Shifted Lean. This Ford-enhanced code applies to F-150, Mustang, Explorer with V6 and V8 engines.
Common causes of P1133
- Small vacuum leak the PCM can no longer fully compensate
- Weakening bank 1 upstream sensor drifting lean
- Marginal fuel pump output at higher loads
- Partially clogged bank 1 injectors
- Minor exhaust leak ahead of the sensor
How to fix P1133
- Smoke test the intake for small leaks
- Compare bank fuel trims under load, not just at idle
- Test fuel pressure under load
- Evaluate upstream sensor response time
- Service injectors or replace the sensor per test results