Kia Rio MIL ON After Engine Replacement
Feb. 02 2021
Feb. 02 2021

Vehicle: 2011 Kia Rio, L4-1.6L, Automatic Transmission

Mileage: 145,009

Problem: This vehicle arrived at the shop with valve damage after breaking a timing belt while the engine was running. The vehicle owner didn’t realize that the timing belt had broken and replaced the fuel pump, hoping that would fix the problem. When that didn’t work, he brought the car in to the shop.

Case Details: The shop replaced the engine with a used one from a wrecking yard. Afterwards, the vehicle started and ran, but the malfunction indicator light (MIL) came on and the same two diagnostic trouble codes (DTCs) kept returning:

  • P0171 – System Too Lean
  • P2177 – System Too Lean Off Idle.

Despite the MIL and the lean DTCs, the donor engine idled very well. While reviewing the fuel trim live data readings at higher RPMs, the tech noticed that the lambda reading was 1.4 at 40 mph, indicating a lean condition. In OBD-II generic mode, that reading was +25%, also verifying a very lean condition.

It wasn’t until the technician spoke to the customer, that he learned that the customer had installed a very inexpensive non-OEM fuel pump. Now the lean condition began to make sense.

Confirmed Repair:

The technician replaced the fuel pump with a higher-quality brand, cleared the DTCs and took the vehicle for a long test drive. The fuel trims were corrected to normal and the MIL stayed off. Fixed!

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