Ford Taurus 96 Codes P0135, 141, 155, 161 and lately 174.

I have 96 Ford Taurus, 140k.
Following Codes P0135, 141, 155, 161 and lately 174 came up upon scanning the vehicle.
First four codes (oxygen sensors) came and a week after 174 appeared.
Any suggestions?
Can all four sensors go bad? Where are those sensors? Can I replace them?
Where is Maf sensor? Should I replace air or fuel filter since 174 came on?

Okay, you'll need to check for battery voltage on all the heater circuit voltage wires. Then ohm check for 3-30 ohms. Then if all checks out, an amp draw on all of the heater circuits exiting the PCM will need to be done to find out if it's a wiring issue or the PCM. Its quite possible it's as simple as a blown fuse or as bad as a PCM. IT's unlikely that all the heater circuits went bad at once.

Same car with same codes except P0174.
I pulled the PCM and put a used one in but still have the same
codes. It took about 30mins for the ENGINE light to come back on
showing the same codes. Customer took to dealer with this problem and
told it needed a new PCM but clearly that didn't do it. I'm looking for shorted wires to O2 sensors now. 4 O2 sensors on this car If you come up with a answer please let me know, I'll do the same. Thanks

First of all, the P0174 code for him I wasn't even addresing, but rather the other 4.
Is your only code a P0174?
Your P0174 indicates a lean running condition. BEFORE changing the PCM or anything else have you checked the forum for all the 0174, 0171 problems that can occur from bad intake gaskets, broken vacuum lines, etc? check there first and post back. You can check your o2 sensor, and if the voltage is stuck at less than .45 volts that could be causing it, but usually would set a code for o2 not switching. If the o2 is switching properly, then that's not it.

It's possible the MAF is throwing alot of things out of whack or a vacucm leak, fuel pressure issue etc, etc! PCMs rarely fail that way!

Hi again, The codes I'm pulling are P0135, 141, 155, 161.
I think my problem points to OX sensor heat circuit failure.
The car is a 1996 3.0 overhead valve engine.
It runs OK but gets rough once in a while. Needs to pass
emissions soon so must get to the bottom of this.
Thanks-

Ok then I'll leave you to it!

Okay, I misunderstood. You'll need to do the above tests then. It's unlikely to be all heater circuits malfunction all at once. Ohm test them, amperage test them and then unplug the wires at the PCM and amperage test the pins. It could be a PCM but to know for sure, you'll need to diag. it properly. If youre not comfortable doing it, then you may need to take it into a good shop.

I tested O2 sensors and found some clown spliced in one of the O2's and crossed wires sending the heat power back into the PCM on the signal side, could this fry the PCM?
I'll put a new sensor in place of this taped up mess and see if I'm in the clear. Thanks-

Yikes, it doesn't sound good. If the 12V supply did in fact fry the o2 sensor input to the PCM, it would explain all the o2 heater codes. Replace the mess and see what happens

HI

Electrical problem for sure ¡¡

As Darkrooms says is not possible to have all the O2 malfunctioning at the same time..
You didn´t told us yet if you already checked all the fuses, you can have some electrical wires that are shorted or making somekind of trouble down the instrument pannel. Have you already checked the electrical continuity and resistance in the O2 wires between engine and computer or to the fuses compartiment.
You should take a look under that instrument pannel and watch all these stuff there.. ¡¡

Yeah, he found a mess of bad wiring inwhich the heater circuit feed(12V) was re routed into the PCMs input circuit.