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.
  • Sponsors(?)


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)
Thread starter Similar threads Forum Replies Date
Eric_WTM Engine P1151 & P1131 appeared and I need help SN95 4.6L Mustang Tech 2
D codes p1131 and p1151 HELP SN95 4.6L Mustang Tech 7
A 2003 GT with P1131/P1151 DTC's. Help! SN95 4.6L Mustang Tech 1
98blackstallion Ok threw a couple codes...p1131 and p1151 Please help.. SN95 4.6L Mustang Tech 15
M P1151 NEED HELP!!!!! How to fix... SN95 4.6L Mustang Tech 0
9 Help! P1151 engine code??? SN95 4.6L Mustang Tech 7
M 302 alternator help is it 1g or 3g? Fox 5.0 Mustang Tech 5
B 88 Mustang 5.0 Help! I’m losing my mind Fox 5.0 Mustang Tech 4
S Electrical HELP !! Driving and just quit... Fox 5.0 Mustang Tech 12
mustangpauly 351w swap need help will not idle Digital Self-tuning Forum 5
T Need help identifying casting numbers 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 7
0 Help putting a combo around TFS 170 heads. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 13
J Engine Help with cold starts and cold idle Fox 5.0 Mustang Tech 3
nickyb Electrical Help ac diode?mine has worn wires. Fox 5.0 Mustang Tech 4
Z Blinker help The Welcome Wagon 1
R help please. Fox 5.0 Mustang Tech 20
ameration Need Help with new 5.0 Purchase 1994 - 1995 Specific Tech 6
M Intake replace help 1996 - 2004 SN95 Mustang -General/Talk- 2
9 HELP!!P0174CODE SN95 4.6L Mustang Tech 9
K Fox GT Fog Light Lens help 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 1
J Need help with qurterhorse and running Digital Self-tuning Forum 1
P 1996 Saleen Starting Issues Help Please SN95 4.6L Mustang Tech 3
C Tech help 2005 - 2014 S-197 Mustang -General/Talk- 0
Nick81 SN95 Help*** 94 mustang gt 5.0l rebuild 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
B new to forum from iowa and dont know how to use it HELP The Welcome Wagon 3
N Help identifying 12 volt ignition wire 2005 - 2014 Specific V6 Tech 1
A Help with valve relief notches in pistons 1996 - 2004 SN95 Mustang -General/Talk- 1
B Help identifying a part 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
L Electrical Need Help Fox 5.0 Mustang Tech 15
M Electrical Help identifying rogue wire Fox 5.0 Mustang Tech 7
A comp cam 2 upgrade help 1996 - 2004 SN95 Mustang -General/Talk- 2
B Need some help cars not right SN95 V6 Mustang Tech 1
J Weird tail light issues (dealer won’t help) 2015+ (S550) Mustang -General/Talk 2
G troubleshooting help car is stumbling and lean 1994 - 1995 Specific Tech 1
H Fuel Line Help 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 10
D Help finding 1991 Mustang 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 8
D Electrical Please Help - 2010 v6 want stat 2010 - 2014 Specific Tech 0
T need help deciding on what cam i should get for my mexican block 302 Fox 5.0 Mustang Tech 8
A Engine 87 EFI 5.0 to my 83 four eye need help with wiring Fox Engine Swaparoo 0
K Help Supercharging 2004 3.9L V6 SN95 V6 Mustang Tech 0
R Need help finding reverse switch on transmission Fox 5.0 Mustang Tech 5
P Help Please 2005 - 2009 Specific Tech 3
H Just got a 2000 mustang gt with a seized engine HELP!! 1996 - 2004 SN95 Mustang -General/Talk- 1
C Engine Performed cranks but no start checklist and no joy. Help Fox 5.0 Mustang Tech 1
J Help with choosing suspension for a 65 with a 5.0 L conversion 1965 - 1973 Classic Mustangs -General/Talk- 4
S CARWASH WASHOUT NEED HELP PLEASE 1996 - 2004 SN95 Mustang -General/Talk- 3
9 Engine 95 5.0 mustang engine problems and codes. please help! (MAF) 1994 - 1995 Specific Tech 9
Q Wire connector identification help 88 2.3L (N/A & Turbo) Tech 2
S Magnum 400 wheels on 78 king cobra * please help * 1974 - 1978 Mustang II Talk & Tech 7
rayray33 Please Help Digital Self-tuning Forum 2
Similar threads