Hello everyone.

I've been looking around on this forum but this is my first time posting.
I have a 98 F150 4x4 with a 4.6 V8 and auto trans with manual transfer.
It has 173,000 miles and runs good with no fault lights or codes stored in memory.

I am trying to get it through NY's emmisions inspection. It had been sitting for a long time and battery was replaced. I went through a drive cycle to bring all monitors up to readiness status.

My problem is every time I turn off the engine my sensors reset and go back to an incomplete status and the truck has to go through a drive cycle again to bring sensors back to ready status. The sensors in question are catlyst,evap,O2 snsr, O2 htr, and EGR. Inspection requires engine to be shut off prior to testing, so I cant just leave the engine running when I bring it in for inspection. Does anyone have any idea where the memory for these sensors is stored and where it draws it's voltage from.
I hate chasing electrical gremlins, any help or suggestions would be greatly appreciated.

Andy

 

Anyone?

 

Its a voltage problem, the battery is weak to where it cant keep it stored in the computer. Even if it starts the truck its still not enough constant voltage to keep the ECU from resetting.

Take it to a place to test the battery, ensure it holds a 200AMP load at 9.6v + for atleast 10 seconds no more then 15. Ive seen a few cars that it would constantly reset anytime the vehicle was shut off because the battery was weak.

 

Thanks IR0NS1N. The battery is old and weak but does start the engine. I'll replace it and see if it helps.

 

If the battery cranks the engine, it has plenty enough power (usually) to provide KAM power to the PCM.

There is a small fusebox tucked into the corner of the fenderwell and the firewall on the driver's side. Open it up (remove the tape if the tape is still on it).

There should be two fuses in it, a 3A or 5A closest to the front of the truck and a 15A or 20A fuse in the second position.

The first fuse is there to supply Keep-Alive Memory (KAM) power to the PCM. Yours is either open, missing, or that circuit is dead. Without power on that circuit, the PCM resets after a few minutes once the truck is turned off.

That fuse box is not identified or described in the 98's owner's manual but it is in the manual for the 97. Use the link in my signature to download a 97 manual for reference.

 

Actually Ive seen 3 vehicles (2 dodge one chevy) that would loose KAM but would still crank over despite a weak battery. After a new battery was installed the ECU never had an issue with the Monitors.

Im sticking to the battery still could be the problem.

 

If its old and weak then you should replace it before it leaves you stuck

 

Certainly better to be safe than to get stuck somewhere....

 

Yep, bad fuse for the PCM as stated by projectSHO89. Water has gotten into the little fuse box and corroded the fuse. Thank You so much for the help and advise...I hate chasing electrical problems. I did replace the battery just to be safe.

 

Old thread, but I'll second spdr8sr's response to projectSHO89, I had the same problem. Took my truck in for inspection, in RI, they told me no can do, OBD2 system isn't ready and that I needed to drive it, I had put 2000 miles on it since rebuilding the eng/trans etc. So I took it home and put my own scanner on it and got error code P1000 and P1605, which lead me to this thread and the fuse and so on and so forth. THANKS!

 

I know it's an old thread but.....

I am getting the P1000 code and I have put over 500 miles on the truck and it's still there.

Is that fuse box mentioned earlier on my truck too??

Going to have the battery tested.

 

That small fusebox was exclusive to the 97 and 98. By 99, the electrical systems had been redone so that the PCM KAM fuse now had a home of it's own. I don't have my manuals handy, but look in your owner's manual. You'll be looking for a small-value fuse, usually 5A or so, that them manual describes as having to do with the PCM. That's usually the one that supplies power for keep-alive memory.