Diagnostic group
Fuel Trim & Mixture Codes
Lean or rich mixture codes usually mean the PCM has reached the limit of how much fuel it can add or subtract to keep the engine in range.
P0170-P0175, P2195-P2198
Codes in This Group
P0171
System Too Lean, Bank 1
The PCM is adding too much fuel on bank 1 because the mixture is lean.
P0172
System Too Rich, Bank 1
The PCM is subtracting too much fuel on bank 1 because the mixture is rich.
P0174
System Too Lean, Bank 2
The PCM is adding too much fuel on bank 2 because the mixture is lean.
P2195
Bank 1 Sensor 1 Oxygen Sensor Signal Biased/Stuck Lean
The upstream oxygen sensor signal on bank 1 appears stuck lean or biased lean.
P2197
Bank 2 Sensor 1 Oxygen Sensor Signal Biased/Stuck Lean
The upstream oxygen sensor signal on bank 2 appears stuck lean or biased lean.