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I have a 1999 Ford Explorer. A P1151 code has shown up. Could it be a vacuum problem or something to do with the MAF? Any help appreciated.
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Here's what I've found for the 1999 Ford Explorer. The P1151 code could be a lack of HO2S-21 switching, or sensor indicates lean (bank 2). Possible causes setting conditions: 1) Check for air leaks after the MAF sensor mounting location 2) Check for air leaks in the EGR system and in its related hoses and/or valve 3) Check for air leaks in the PCV system and in its related hoses and/or valve 4) HO2S connector is damaged (check pins for damage, and for moisture) 5) HO2S signal circuit open, shorted to ground, shorted to voltage 6) HO2S has failed (it may be contaminated with fuel, silicone or water) 7) Low fuel pressure or vehicle driven until it was out of fuel 8) Vacuum hoses leaking and/or damaged 9) Engine running in Closed Loop; and the PCM detected that the Bank 2 HO2S-21 signal was less than 0.450v. In this case, the PCM is "correcting" rich for an overly lean condition. This code sets in 2 Trip(s). This code will turn on the MIL (Malfunction Indicator Lamp)
It is an oxygen sensor code. P1151 OBD Trouble Code NOTICE: The information contained on this site is presented for information only. OBD-Codes.com is not responsible for any actions you take on any vehicles. If you have any doubt as to repairs on your vehicle, please contact a qualified technician. Technical Description Lack of HO2S-21 Switch, Sensor Indicates Lean What does that mean? A Heated Exhaust Oxygen (HO2S) sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time. Symptoms You will likely not notice any drivability problems. Causes A code P1151 may mean that one or more of the following has happened: Electrical: Short to VPWR in the harness or HO2S Water in the harness connector Open/shorted HO2S circuit Corrosion or poor mating terminals and wiring Damaged HO2S Damaged PCM Fuel System: Excessive fuel pressure Leaking/contaminated fuel injectors Leaking fuel pressure regulator Low fuel pressure or running out of fuel Vapor recovery system Induction System: Air leaks after the MAF Vacuum Leaks PCV system: Improperly seated engine oil dipstick EGR System: Leaking gasket Stuck EGR valve Leaking diaphragm or EVR Base Engine: Oil overfill Cam Timing Cylinder compression Exhaust leaks before or near the HO2S
I had this code and it was the heated oxygen sensor, bank 2, right before the catalytic converter. 100% fixed!