coolride

Hi All, new here! But not new to Ford by any means. New to the electronic issues they have though!
So I recently bout this 2003 F150 with 4.2L 5spd. 75K miles.
Engine light is on. Guy told me it has O2 sensor issues, and gave me 3 of the 4 sensors for it.
I check codes. P1633 comes up. Nothing else for codes.
I expected O2 codes at least. I found 1 rear O2 sensor bad due to wires rubbing on heat shield. I replaced it, and found that front converters are gone, and rear converters have been gutted. Not good. Had to pull left side front pipe off to re-tap O2 hole, thus the discovery of the empty cat. I put the new O2 sensor in for now and re-installed exh.
The truck runs extremely rich on the right side of engine, but the left doesn't. I discovered that by starting it before I put left pipe back on. Right side blows blueish fuel smoke, wreaks of gas. It does this when you start it and if you hammer the throttle. So before I go spend $500 on new cats, I was hoping someone could help me with the rich condition. I was thinking of doing the front O2 sensor on that side and see if it helps. Not sure it matters doing the rear one until I deal with the cats.
And then the 1633 - keep alive code. With this condition, what will it cause to happen? I checked the easy stuff, fuses, relays. So far they check out. I know I will need to dig deeper. Is it worth paying Ford to take a look with a scanner or will that just cost me $150 to have them tell me its a wiring issue? I know that's hard to say. It just had a new head rebuild on the driver side due to a stuck valve. Its possible a harness got damaged somewhere. I will be looking into that next.
Thanks for any help or ideas of what to look for. I was also going to try finding the IMRC linkage and be sure its attached, its a bugger to see!

coolride

Am I posting in the right place?

Frank_Ford

the P1633 code is telling you that your PCM is not getting the voltage needed to function properly Specifically, send the proper fuel air mixture to your engine. Things to consider to fix this is

How is your battery and all battery connections

Is there corrosion on battery connections at battery or on the firewall

Is you PCM getting a good connections. You could disconnect the cable to the PCM, inspect it clean if necessary Put di electric grease on the pins to make sure you are getting a good connection and carefully plug it back in

be on the lookout for any other possible problems like coolant on wires and cables, lots of grease and oil on cables, anything that could be causing a bad connections in getting power to your PCM.

The fact that you are having problems with your cats and Ox sensors is being caused by the PCM sending the rich fuel to your engine so you have to get the PCM fixed and your Ox sensors will start giving normal readings

It could be a bad PCM also if so, you can go out on ebay and buy a used one that has a guarantee for about $200

coolride

Thanks for the info Frank. I will get to it this weekend. The battery is a bit weak. I will replace it. The connection issue may be the issue. I can clear the fault while the truck is running and it just pops right back on instantly.
I will post again after I look into it this weekend. And hopefully I will find something that will help me solve it. Also thanks for the info on how it will make the truck run so rich. I won't spend any more time trying to figure that out until the PCM is dealt with.

Jbrew

That's an unusual DTC, -

P1633 KAM Voltage Too Low

Refers to the KeepAliveMemory of course.

Franks got it covered, but also check that PCM ground on the firewall. It's on the firewall right in the corner. Last ground on that side, they can get fairly corroded with time. You'll have to pull the battery to get to it. Wire wheel that 8mm green bolt on the backside, clean the connector and firewall area as well.

coolride

OK I will make sure to look for that as well.
Thanks for the advise. I will be sure to post what ever I do find if anything so hopefully it helps someone else if they encounter this.
I just bought the truck this way so I have no idea what lead to it. I was told CEL was on due to bad O2 sensors, and they gave me 3 new ones to go with it. Got home, pulled codes to find this surprise. I will get it figured out soon. Can't really drive it like this so have no choice. Is there any way for Ford to check the PCM if I find nothing?

coolride

Before I tackle this investigation, I was looking for the PCM pinout so I can test voltage and grounds in case I don't find anything obvious. I can't seem to find a pinout for a 03 f150 4.2l. I keep finding pinouts for diesel or 3.0 or 4.0 stuff. Anyone have a good link or even a picture of a pinout for the 4.2L with manual trans?
Or is my best bet to pull the PCM and get a model number off it?
Thanks

coolride

OK so I have spent some time looking at this truck. Fuses and relays are good. Battery terminals are good. I charged battery for a day before touching it just to get through these tests. I will be replacing the battery soon but I don't think it is causing my issues here. Grounds are good and harness looks to be good. Everything is pretty clean, no oily stuff on any wiring. I took out battery, pulled PCM plug, cleaned PCM and harness plug. I put battery back in with PCM unplugged. The PCM harness has 2 hot wires with full voltage and 1 with about 5.5 volts. I also found that 1 PCM fuse in the truck has 5.5 volts with key off. I didn't find an accurate PCM pinout for a 2003 f150 so I don't know if the PCM is missing power at a pin? I put it all back together and it still has the P1633 code. I clear the code and it is right back. So I haven't helped it any yet.
I am wondering if the PCM is toast? IS there really an accurate way to test it? Or is that a Ford dealer thing?