P1178 — Mixture 2 strength (multiplicative) fault

Diagnostic algorithm

1. Verify the code and capture freeze-frame and live data. Note whether problem is present at idle, cruise or under load.
2. Check for related DTCs (O2 sensors, fuel trims, MAF/MAP) to narrow focus to sensors, air metering or fuel delivery.
3. Visually inspect intake manifold, vacuum lines, PCV, and all hoses on bank 2. Repair any leaks, then clear codes and retest.
4. Inspect wiring and connectors for bank-2 O2/lambda, injectors and air metering sensors. Repair or secure any damaged wiring or poor connections.
5. Test fuel pressure and volume. If pressure is low or fluctuating, service fuel pump, filter or regulator and retest.
6. Check MAF/MAP sensor readings for plausibility. Clean or replace MAF if contaminated; replace MAP if out of spec.
7. Monitor O2/wideband sensor output for bank 2. If sensor is slow, stuck, or out of range, replace the sensor and re-evaluate fuel trims.
8. If trims remain abnormal after sensors and fuel supply are verified, perform injector balance/flow testing and inspect exhaust for leaks or catalytic restriction.
9. After repairs, clear codes and perform a full drive cycle to confirm the multiplicative correction returns to normal and code does not reappear.
10. If problem persists and wiring and sensors are confirmed good, consider ECM software update or replacement as directed by manufacturer diagnostics.