I have two separate problems. I'm getting a PO171 code. The second problem is a warning light saying Cruise not available/ Check rear lights. When we check the lights,they are all working. The cruise won't work when the warning lights are flashing. If we shut the car off and restart, all works fine, and warning lights are gone.

 

DTC P0171
FAULT DESCRIPTION A bank combustion too lean
MONITORING CONDITIONS Engine at normal operating temperature
drive at steady speed > 40 mph;
engine speed 1300 – 4500 rpm
> 1 minute 20 seconds

 

What's the probable cause? O2 sensor? I understand the rear light thing is probably the brake switch

 

P0171 causes:

- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

Help with this

Read more: P0171 Jaguar System Too Lean Bank 1 OBDII Engine Light Trouble Code | Engine-Codes.com

 

With the cruise not available I would say to check the brake switch. Because you do not have P0174 with your P0171 I would say to check the 02 sensor