I have a 2004 F150 screw, just this week the door locks started going wonky. Use the key fob to lock or unlock doors and it MIGHT work once then nothing, as well as the parking lights don't do the customary one flash but flickers. Does the same if I use the door pad and the lights on door pad flicker and I hear a slight buzz from in truck. It won't lock or unlock doors from switch on door panel either. Could it be a ground issue??

 

All door lock functions are controlled by the "Body Control Module"/"Body Security Module". In a 2004 Super cab/crew, this module is mounted behind the rear seats. It looks like the BCM has 2 grounds, One on the rear wall of the cab, and one behind the driver's kick panel (I would check this one first, it is fairly easy to access and is prone to corrosion). It is also fed by 4 fuses, #06 #18 #40 & #107 you can check if any are blown. If the grounds and fuses are good, you may have to pull the rear seat back and start testing the connectors/ground at the BCM itself.

 

Ok so a update Shadow. Sorry it took so long to get back we had a major storm and it blew a couple towers for our internet down. I removed the rear seat and the drivers kick panels, I took a mini grinder and cleaned the grounds and wires up. 2 on kick panel and 2 at BCM. I thought I had it as I used the fob about 30 times and light lit as normal when unlocking and doors locked and un locked as normal. Went out the next morning and when tried to unlock instead of light coming on and staying lit they lit but flickered and the BCM would click like mad. Wifey called me at work and said battery was dead so had to boost it, and as she was driving home and turned in driveway the BCM was clicking and the lights were flickering. I unplugged the BCM thinking hey that will stop it, Well she was not happy as then all she had was daytime running lights to drive to work at 5 AM. Ill have to go out and find what fuse to pull to stop door locks and not screw other stuff up. Any help is appreciated. I tried to use ohm meter and check the ground wires on BCM I put one probe on ground wire and other on the ground wire I cleaned and it beeped so it made a circuit dont really know what else to check?? reading those shematics was impossible as it didn't show the wirer positions?

 

As far as the headlamps are concerned, the BCM only controls the auto lamps, turning the headlamp switch to the headlamp on position should turn the headlamps on regardless of the BCM. Power passes directly from the headlamp switch, through the multi-function switch (Dimmer switch), through 2 fuses (one for each headlamp) and to the lamps themselves.

How old is the truck's battery? I know a weak battery can cause strange electrical issues.

Maybe one of the power feeds to the BCM has a bad connection and is causing the BCM to power off when the load of the lights comes on? If you can reproduce the problem regularly, I would back-probe the BCM power connections with a test light and check if one of the constant power feeds to the BCM is dropping out when it tries to turn on the lights/unlock the doors.

What do you mean by the diagrams don't show wire positions? Are you looking for the connector pinouts? Here are the connector pinouts for the BCM:


2004 F150 BCM Connector Pinouts, C3008a is Blue, C3008b is Green

 

The Battery is only a year old and tests well, connector pin out pics are exactly what I needed lol. I didnt look at headlight as of yet, Wife just said she had no high beams and lights were really dim so im assuming they were not on. I'm off today and Ill look a bit deeper and try to replacate the clicking and flickering and then I will try to have a ground in the right spots in the connector pin out plugs then ground the wire directly to see if that stops it. thanks for your time. I was just outside and checked the lights and they are working just fine?? I'm not sure what she was talking about. *sigh* its hard to diognose things when I'm getting/ giving false info . im sorry about that.

 

Sorry to be a pest. I have been on it since this morning here here is what is happening. The headlights seem fine can't replicate. I had power at the BCM behind back seat at the spots that are required to as well as the ground were grounding there as well. I pulled front seat out, and in harness was a set of wires that run to back behind back door and it had 4 wires in it as well as a bare wire that was for ground and that set was wrapped with a silver looking tape. The bare ground was corroded all the way up to drivers kick panel, to the whit junction so I replaced the whole ground and soldered in new one and retaped it completely. Not working still. I have no power going to the door lock switch, the interior lights are not coming on when doors open and if you turn on ignition and play radio then shut ignition off the radio keeps playing even though doors are open. It had that problem when I bought the truck when it was 4 years old and a garage fixed it and said was a cortroded wire inder carpet. I can't find the wire or previous repair?

 

Hmm, I don't think there should be any bare wires in the truck's harness, I wonder if that is the previous repair. I just pulled the threshold of my truck to look at the harness and there don't seem to be any bare wires, mine is a super cab but I would think this is the same for a crew.

There isn't a power feed to the door lock switches, the Pink/Yellow and Pink/Lt Green wires are monitoring for a ground. If you have an incandescent test light, clip the wire on a good body ground and touch one of the Pink wires and the BCM should Lock or unlock the doors (Pink/Yellow is lock, Pink/Lt Green is unlock). The open circuit voltage at these wires on my truck is about 0.5 Volts.

The no dome light and radio playing after the door is opened are probably related. The dome lights aren't coming on when you open any door? I would be checking if you are getting grounds from the Door Ajar switches at the BCM, If all your door ajar switches are properly grounding pins 4,5,12,&13 on connector b then there may be a problem with the UBP communication bus between the BCM and the Instrument Cluster. You could try checking for an open circuit/bad connection on the UBP wire between pin 3 on connector b @ the BCM and pin 3 of the Data Link Connector (OBD port under the dash). The BCM monitors the doors and communicates with the IC over a serial bus (UBP). The IC actually controls the dome light and Accessory Delay Relay.


Data Link Connector

 

Hi Shadow 351.
Well it has been a long and very informative trip!! The wire with the bare ground in it is buried in the harness and I found out its for the sunroof we think and its silver metal tape wrapped for interference. I found my corroded wire and I couldn't have done it with out the diagrams you supplied. The blue plug on the BCM pins 7&8 say Voltage supplied at all times. Well I tested it once with a standard test light and it had power, I bought a smart test light that plugs in your lighter and when you touch ground it lights green and when you touch power it lights red and the better the ground or power the brighter the light. well it turns out pin #8 had limited power so put 12 volts to the 8 pin and voila everything worked. I traced the green and yellow wire to fuse panel, about 2 feet from panel I bared wired and tried the 12 volt to it and nothing so I replaced that wire to BCM and fixed problem and when I pulled old wire from harness there was a little bulge in the wire and a small hole that looks like someone poked it with a test light in '08 during previous repair. I put the complete interior back and has been ok for 2 days. So in closing thanks again for your patience and knowledge.
Dave

 

Good, I'm glad it's all sorted.