i have a 1999 ford f150 4x2 4.6 auto, and i been driving it fine the past few days after i addressed the small issues with the alternator, i drove it 40 miles round trip last night, got up this morning to crank it, my gauges dont sweep or come on, odo doesnt come on, only the door ajar and abs light comes on. No start but it cranks, and i have switched around relays and checked fuses and there is nothing wrong there.

i feel like i got gremlins again



i pulled the pcm out and checked the connections to see if that was the problem , but no visual problems there, i checked the pcm fuse and it looked good too, tested it with a voltmeter and got batt voltage.
i might be overlooking it,
only the door ajar, and abs light came on the gauge panel, and nothing else when i have key on engine off, i checked every single fuse, swapped the relays around inside and outside, still nothing. i did leave the key in a few seconds ago for about 2 mins then the gauges came on, theft light rapid flashing, and odometer had dashes, but after i tried to crank the truck, it went back to nothing on the cluster except the door ajar and abs light. i dont have a spare key to test with

 

also would a dirty ignition lock cylinder cause the key not to register with the pats transceiver? i pulled them out and it was really really nasty in there

 

Please understand your key has nothing to do with the dash not coming alive.
There is a power issue at some point causing the voltage to go too low for the dash and the PATS system.
This is why there is a no start.
Leave the PCM alone. You can't test it in anyway, it's not the problem.
First thing to do is make sure the battery cable terminals and cable ends are scrubbed clean and put on tight.
The dash should come on for full lamp checkout with the ignition to run only before cranking.
If not, the dash power has an issue.
If yes but goes by/by at cranking, there is a power issue back toward the battery that the high starter current draw is causing a huge voltage drop to occurr.
Both these situations will render a no start because the PATS power is affected as well.
Good luck.

 

so it being, key on engine off, i would have a current draw when i energize the system? correct?

 

Absolutely.
Your powering up the computer, the dash, the PATS, the fuel, pump, the GEM modual at a min.
They all like the same 'food'.
Good luck.

 

ok thanks again bluegrass, ill keep you updated. sorry if i bothered you or anyone else. i know what im doing i just jump to advanced conclusions too fast sometimes. =-/


your help is much much appreciated.

 

ok so , here is what i did today, i put everything back together, checked all my power, which was good on that side, cleaned the cables and turned the key on , still no guage sweep, or activity, only the abs light and door ajar.


now


if i leave the key on engine off for about 1 -2 minutes with the key in the ignition, everything comes on, except the odometer is dashes and theft light is flashing, would that constitute a new key? i mean i was driving it fine the day before, and when i went back outside to start it the next morning, it started giving me the problems i have now.

 

i also had another pats type key in my pocket with my truck keys, would this cause an interference with the chips?

 

The dash power issue has nothing to do with a key.
The key works with the PATS only.
Sometimes if you have another key or some other item on the same ring it may cause trouble with starting but not with a power issue to the dash.
At this point, there may be a problem with the circuit board on the back of the dash insturment pod.
This is a known issue for some trucks after they age.
Good luck.

 

ok bluegrass, you were right about the dashpower. i did a pinout test with a voltmeter on the cluster harness side, the side that goes into the cluster, and i got good readings except one wire, the red light green wire , first step of diagnosis was no communication with the HEC module , so i went to tearing the cluster out and unhooking it to see what was going on , i got 10+ volts to the red white/green yellow/but got to red light green, and i was reading .36 MV on my voltmeter, so i found the culprit i hope. gonna either pull the dash to see if i can pull the harness out and fix that wire or see if i can fish it out from behind the dash without removing it out of the truck.

thanks again, i need to KISS more often, keep it simple stupid. i hate when i overlook like this.
i owe you a beer, and crawfish

 

Not a problem. Glad you traced it out.
I have more than 50 years of circuit trouble shooting so it gives me a little logic edge as long as I get accurate feedback.
Good luck.

 

heh yea the years behind you make a very large difference. sorry if i was vague on my description. i looked at alldatadiy, and it says the red light green is the power, for the start/run side of things, so i am losing power in between that and the fuse box in the truck. Makes me feel a whole lot better knowing i dont have to get the pats system messed with.

now for the flow of the system, when you do key on, should it be pats on, to cluster then talk to pcm to say yes to the injectors/fuel/ignition

 

Key to run powers up the PCM through a relay.
The dash power comes on through other fused contacts of the ignition switch.
They all get power in about the same time frame of milli-seconds.
The PCM has to begin signal processing so it can accept the PATS signal while the dash processor is doing a self check-out.
All seperate operations but so fast you can't see the differences in time.
You would not have any reference to see the time difference that fast.
Actually the slowest element in the whole operation is the pull-up time the relay takes to get it's contacts closed.
Good luck.

 

i have something that's been bothering me, i never knew that maybe ford had a built in audible diagnosis for the cluster being bad, cause when i took the cluster out, and did the pin tests on the white connector, when i hit the bad wire, the audible beep noise that you hear when you turn the key on, started beeping alot. even though i wasn't reading the correct voltage off of the red/light green wire on the harness.