The 172 & 173 codes are indicating a lean condition on both banks.
Might be a good idea to check all vacuum hoses and there are quite a few, for cracks or leaks.
The other 2 codes don't seem to apply to your vehicle.

 

Ok, you've got some work to do, but not to worry, I cut my driveabiltity teeth on these models. I loved working on them, as they came from the days when you could go home and feel reasonably sure you fixed the damned thing.
The 172 and 173 are why you aren't passing emmisions; I'm sure (at least I hope so) that you've checked the fuel pressure, and it's around 30-45 psi with the eng. running, and no fuel being sucked into the vac. hose.
The 172 means the O2 sensor was stuck lean, and the 173 means it was stuck rich. How can this system be stuck at both extremes? It's got a wiring problem.
This body truck has an o2 loom that's built into (and wraps around) the battery pos. cable that goes right to the starter; the last stop is the o2 sensor, at the end of the rainbow, so to speak.
Acid from the battery gets onto the wires, and even if they look good, will short wires together or eat the copper out of them and open a circut. A dead giveaway to this is the insulation from the wires look either white/faded or puffy.
The o2 sensor voltage is very easily accessible (if you'd like to make a liar of me; i always give people a way to defeat me to make it an even fight). There is a (usually) white, 4 pin connector, with the battery cables, right under the starter solenoid. These are the 4 wires to go (further down) down with the cables to the o2 sensor. Put the neg. lead of a DVOM on the neg. battery terminal, start the engine, and within 2 minutes, while backprobing the (I think) gray/lt. blue wire. This is the o2 output to the pcm. It should be switching from rich (>.45V) to lean, and back.
I'll bet it's not, or it's reading batttery voltage (which is supplied to the heater in the o2, which were also in that same harness (like a pink or purple wire and black; the other wire is a signal return, to a seperate ground, just for the o2).
This was a very common problem, and the cables came with the looms years ago, but they're not aviailible anymore. So, if you remove the cables, you can cut and splice and make a new loom for yourself and use the o.e. pins and connecoters, and there you go.
The o2 sensor usually got whacked out from all the power running all over, so don't be surprised if you have to replace it.
The 632 means the O/D cancel switch cycle wasn't detected (Ususally only set on a KOER, when the switch wasn't pressed). If it doesn't work, check the fuses, then this most likely means that the wiring to the switch in the gearshift lever is open (common).
The 536 means the stoplamps weren't acitvated during the KOER (again, usually caused by incorrect KOER procedure).
Please let us know how it goes.

 

One other thing; these trucks were always a bitch to get through a smog, test, so, just to make sure you have the best chance of passing;
1) MAKE SURE there are NO misfires (this will cause high HC)
2) Make sure the t-stat is letting the engine get hot enough. If it's opening too early, the ECT never sees a warm enough engine, which adds just a little fuel, which will (over time) ruin the catalysts.
3) Take this truck in with a really hot engine. Even in the waiting line, I'll run these at 2k rpm until I have to shut it off.
4) If you have an infrared temp. sensor (very inexpensive), measure the temp of the exhaust inlet and outlet, with the engine running at around 1500 rpm. There should be at least a 250 degree warmer difference at the outlet (this is called a delta-tee test, and test whether or not the cat is functioning). Do this after everything else is fixed.
Good luck!

 

Greasmark, thanks for correcting the info I posted earlier regarding the 173 code.
My source indicated for a 5.0 L engine without E4OD that 173 was a lean indication which we now know is incorrect because the same code for a 5.0 with an E4OD shows a 173 code as too rich. This is how we get into trouble with incorrect info.
Thanks, hanky

 

it very well could be the cat starting to clog up or a vacuum leak ! some vacuum leaks don,t show up until the engine gets to a certain temperature !

 

it very well could be the cat starting to clog up or a vacuum leak ! some vacuum leaks don,t show up until the engine gets to a certain temperature !
How does that explain o2 stuck lean..and rich?

 

Great thanks for the information. I fixed 90% of the problem by changing the cap,rotor,wires and plugs. One plug was not firing at all...I pulled the plug off it was badly corroded. It starts and runs "good/ok" but it has a mis every now again. It seems to idle ok but at about 1500 rpm or so it has an occasional mis. At higher RPM it seems good. Not sure what it might be.

Thanks again for the insight

 

I have a rough Idle on a 302. I have good plugs and gaps, new cap and rotor, new vacuum lines. When I pull the vacuum hose off the brake booster then engine smooths out. It seems as if it is starving for air or running to rich. I have no idea what could be causing this. If anyone knows anything about this please let me know