New Member
Jan 25, 2018
okay so I’ve owned this mustang for about 6 months now and I’ve been driving it with the check engine light on for o2 sensors code. (The originals h pipe with cats were taken out for no cats) I recently got 2 new o2 sensors for the front of the exhuast and used the old sensors for the back, but attached mil eliminators between the wires in the back. I still had 8 codes for heated and regular oxygen sensors. I checked to see what else could be the problem. Found under my dash that a 20 amp fuse blown, labeled “Engine Controls” I then replaced the fuse with a new 20 amp fuse. Reset the monitors and dtc’s drove around the block and the car runs like absolute dog :poo: smells very rich. When heavy throttle car feels like normal but under normal driving with load the car stutters and barely feels alive and has no power. The only code available is p1151 [lack of HO2S21 switches sensors indicates lean] (pending). What bothers me is when I take the fuse out of the car,the car runs totally fine again but then I have 10 codes pop up for oxygen sensors as well p0443 [evaporative emissions systems purge control valve circuit]. And also p1451 [eveportive emissions system vent control circuit] I am running out of time for inspection and need help diagnosing the problem here.
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SN Certified Technician
Aug 14, 2009
Houston Texas
I give up. What model year Mustang are we dealing with here? The fuse panel layout is very different between 1996-1998 and 1999-2004. Just in case this is a 1999-2004 model year.

1999-2004 MY fuse panel schedule:

It's quite possible that the EVAP DTC's are related to the blown fuse. So we have to stop thinking that it runs fine with a fuse removed and start trying to fix the issues with all systems working.

Start first by checking the battery and alternator. Here's some information:

Howto perform charging system voltage drop test

Next confirm that the fuel pressure sensor (FRPS) intake vacuum reference line is connected and leak free. Inspect the line for evidence of raw gas.

Clean the MAF. Use only a product designed for the job.

The "possible cause" for an P1151 are very long. Best to start with the "basics" and then work through the list. But if you have an ODB2 scanner that can read operational PID's, it might make short work of this problem. Here's some information on an affordable Windows based ODB2 scanner.

ForScan ODB2 scanner w ELM327 USB

>>From Ford service manual
P1151 - Lack of HO2S-21 Switch, Sensor Indicates Lean
  • Electrical:
    • Short to VPWR in harness or HO2S
    • Water in 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(s)
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