P0171 and P0174 in 2008 Range Rover HSE

Question

I have a 2008 Range Rover HSE with 147,000 miles. I got a check engine light and the PID indicated catalytic converters in bank 2 were bad. I replaced the cats and then started getting P0171 and P0174 messages. I replaced the air filter and the MAF sensor and still getting the same messages.

The freeze frame info from the OBD scanner is as follows:

  Fuel System 1 CL
  Fuel System 2 CL
  Load %    47.8
  ETC°         189.0
  SHRTFT1   7.0
  LONGFT1   12.5
  SHRTFT2   -0.8
  LONGFT2   10.2
  MAP (inHg)    19.8
  RPM           1322
  VSS (MPH) 24
  Spark ADVC°   33
  IAT°          75
  MAF (lb/min)  2.930
  TP(%)        20.0
  RUNTM (SEC)   157
  EGR_PTC(%)    48.2
  EGR_ERR (%)   0.0
  EVAP_PCT (%)  36.1
  FLI (%)   45.9
  BARO (inHg)   29.2
  VPWR (V)  13.964
  Load_ABS (%)  42.7
  EQ_RAT    0.961
  TP_R (%)  8.2
  AAT (°F)  54
  TP_B (%)  36.1
  APP_D (%) 28.6
  APP_E (%) 28.2
  TAC_PCT (%)   30.2

Can anyone tell me what to look for or what to replace at this point?

score 1 · Answer 1 · answered Jan 04 '18 at 09:47

In general, these codes indicate that the ECU receives information about fuel mixture being too lean, ie. too much oxygen, too little fuel. Therefore, it is trying to compensate by adding more fuel (see the long term fuel trim values which are pretty high). This is done according to A/F sensor readings.

Things to check:

MAF - hypothetically could be faulty, although new.
exhaust leak - oxygen getting into the exhaust system, confusing the A/F sensor. The mixture actually is not too lean but due to false sensor readings, ECU thinks it is. In my opinion not very probable option.
intake vacuum leak - unmetered air getting into the mixture (unmetered = after the MAF)
fuel pressure - fuel pump may not be providing enough fuel pressure
fuel injectors - might be clogged, not letting enough fuel into the intake

P0171 and P0174 in 2008 Range Rover HSE

1 Answers1