danjc3

Summary: all 4 O2 sensor codes hit at same same, looking for causes and fuse.

Back story:
I am working on my Dad's 1998 GT, with 25,350 miles. All original mechanical (engine, tranny, and exhaust). He has done body work, ground effects, lighting mods, and the like - but all changes are "cosmetic".

Last summer the fuel pump went out, and that was replaced with no issues. Late last year (Septemberish) he told me the CEL came on. When I checked the codes with a cheap reader, I got codes for all 4 oxygen sensors. They are P1151, P1131, P0141, P0136. Since winter was coming, and he doesn't drive it during the winter, I figured I would put it off until spring - and guess what spring is here!

So prior experience tells me that all 4 going at same time is a fuse or wiring issue. I got under the car (real chore as it is seriously lowered), and looked things over and found nothing obvious. I have multiple scanners with me now, and have been checking everything, and everything seems to be operating normally. I am obviously not able to attach to the O2 modules, as it appears they were not implemented in the 98 model.

Are they any known areas where wiring defects (rubbing etc) occur for this? I also need to find the fuse, but all fuses are checking good (fuses both under hood and under dash). Is there any known issue that could cause all 4 to fail at the same time?

Thanks to all - as it looks like this is a great group!
Dan

RMK01GT

"lighting mods" always scares me, check any part of the harness where he might have cut into

danjc3

I will (and have been) looking at the mods, to ensure nothing involved there. The light mods are actually the least of my concerns, as they were done by a group of Ford engineers in 2002 timeframe. They used his car to flesh out some of their ideas, and he knew several of them. Living close to Detroit used to have benefits

But - that is a another great recommendation that i will make certain to investigate.

Thanks!
Dan

petrock

All 4 sensors didn’t go out. Your codes are primarily the upstream & downstream sensors in Bank 1.

http://www.obd-codes.com/p1151-ford: Lack of HO2S-21 Switch, Sensor Indicates Lean
http://engine-codes.com/p1131_ford.html: Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
http://www.obd-codes.com/p0141: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
http://www.obd-codes.com/p0136: Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)

swarthyfellow

Sounds like it is a bad O2. I suppose you could have a vaccum leak on bank 1 but I don't it.

petrock

A bad O2 sensor wouldn’t cause the other sensor to also go bad. Chances are high that this is a wiring issue since it is effecting both sensors. All 4 codes indicate a wiring issue. It’s like the old saying goes: Mechanics go to the part while electricians go to the wires.

danjc3

I live out of the area from him, and just got back to looking at this again. I am an electrical engineer by education - but haven't worked in that field for years, so I started with the wires (guess old habits?).

Anyway, I am looking for vacuum and wiring issues, have nothing so far. All fuses show good, wiring channels are intact, and all modifications that are near wiring check out - no rubbed wires or similar issues.

I will continue to poke at this for the week, and will let everyone know what I find. I am starting to suspect an actual failure of the upstream O2 sensor on bank 1. Seems like everything can be explained by this one failure.

Thanks for the inputs!
Dan

WhiteFoxGT

you have no way of pulling live data on both front 02 sensors? You should be ably to pull voltage readings from all 4 sensors.. 98 had that capability.

I'd suspect a bad 02 on bank1, but also i'd be willing to bet you have a vacuum leak at the intake or vacuum hoses going to the intake. Since you have all those scanners, go through the live data and find the voltage for b1s1, b2s1, and also tell me what the LTFT and STFT (long term and short term) fuel trims are. Vehicle needs to be running to get these readings

danjc3

I have a scanner that will show trims, and I actually saw that data. But, I do not recall seeing the voltage levels - I will check again. Thanks!

Manderson

This is an FYI add-on to this thread. My 02 GT threw codes P0171, p0174, p1131 and p1151 codes simultaneously. Had a cracked "S" shaped hose running to the lower right side of the throttle body. Not easy to see since it is under the intake vacuum hoses.