My Highlander has about 170,000 miles, and recently the P0171, P0174, P0037 codes have come up. I replaced the MAF sensor based on some advice and reset the codes, but the P0037 code returned and I imagine the others will as well.
I was wondering if these 3 codes together indicate some common problem?
P0171: System too lean bank 1
P0174: System too lean bank 2
P0037: H02S Heater Control Circuit Low Bank 1 Sensor 2