1997 ford f-150, 4.6 L, Automatic

Running into an issue with multiple components not working:

Odometer
Speedometer
Low Beam HL
Brake Lights
Fog Lights
Turn Signals
Hazard
Truck sometimes has issues starting or stumbles when running if I hit a bump, hit the steering wheel or even slam a door.

Fuses 16, 20, 21, 26, 27 and 28 have no power to either side (fuse box inside the cab, test light used to check). Fuses are good as near as I can tell. All of the fuses in the power distribution box under the hood are good. I recently replaced the GEM in this vehicle when this problem occured - I pulled it back out an double checked every connection and everything looked ok. I also replaced the MFS/turn signal thing.

Could the blue flasher relay under the dash be causing an issue? Any other thoughts/ideas of things to look at?

Thanks for the help in advance

Zack

 

Start at the fuse box inside the truck and work back toward the battery from there. There is generally one main hot wire that feeds a fuse box. Locate that main hot wire (will generally be about a 4 or 6 Ga. cable). Shouldn't be too hard to trace where that hot is being lost if you trace it back to the battery that way. Often the fuses that are only hot with ignition are controlled by relays, but not always. I use a Power Probe 3 and love it. I prefer the Power Probe to a DVM because you can also check voltage, ground, continuity and quite a few other things as well as introducing hot and ground when needed.

 

Odometer and Speedometer are mechanical items on the 1997 ( 97-98 MY was the last of the gear change for changing the speedo ).

1. Low beam HL, is this Left as in Driver's side ?
- The fuse for it listed below, you need to have the main headlamp switch on, to have power to the fuse to check it while installed with the pins on the back with a meter or test light. Turn on the headlamps, and make sure the MFS is in the low position, and check the fuse while installed for power on both sides. If there is, next is to check the bulb connector, Left side is the Dark Blue w/ Wire stripe wire. If that tests good, burnt out bulb.

2. Brake lamps
Is this all 3 brake lamps do not work ?
Does the truck come out of park after starting it ? ( 97 the shift interlock is the same circuit as the brake lamps ).
Try tilting the steering wheel all the way up.
- Some times the MFS connector will get tight, and pull the connector apart behind the knee panel.



3. Fog lamps
did you check the fuse for the fog lamps ?
There are 2 of them, need to have the headlamps on to check the fuse for the fog lamp relay.
When you have them turned on, check the bulb connector for power ( could be blown bulbs ).

4. Turn Signals
- Same as the brake lamps with the MFS connector
- This is assuming the truck will shift out of park after starting it

5. Hazard
- Same as the brake lamps with the MFS connector

6. Truck sometimes has issues starting or stumbles when running if I hit a bump, hit the steering wheel or even slam a door.
- Check the ground connections under the hood, and in both kick panels for a loose ring terminal / screw. If you are having intermittent ground connections, this can cause a few issues. I think there are 5 under the hood ( vague notion this is the count ).

7. Fuses 16, 20, 21, 26, 27 and 28 have no power to either side (fuse box inside the cab, test light used to check).
7.1. Fuse 16 is fed from the main headlamp switch in the headlamp position , and the MFS pushed forward, else it is dead.
- could also be an issue if the tilt up cures the symptoms above
7.2. Fuse 26 & 28 is fed from the main headlamp switch in the headlamp position, and the MFS pulled back ( low beams ) for the left & right headlamp fuses to have power ).
7.3. Fuse 20 shows as the Clutch pedal position switch for manual transmissions only. The circuit is fuse #21 to the starter interrupt relay if you have the Remote Antitheft option or is direct from Fuse #21 to the Clutch Pedal position switch or CPP jumper for the auto trans, and is hot only in the start position. ( run & assy it is dead ).
7.4. Fuse 21 is hot only in the start position, so unless you have a meter on it when you are starting the motor, it will show as dead.
7.5. Fuse 27 is fed from the main headlamp switch in the headlamp position via the MFS in the low beam position powering the fog lamp switch for the fog lamp relay. With the headlamps off, this fuse will show dead.
- Could be testing error or could be part of the MFS connector issue if present.

 

Thanks for the info, The flasher relay doesn't appear to be an issue. I swapped it with a working part out of a friends truck and no luck. This is great info that I am going to dig into this afternoon SScully. Appreciate the help. I will post back what the issue was if I am fortunate enough to find it.

Zack

 

Tried everything that you suggested. When I turn on the low beams with the truck on, still no light in the front left or right and no power to the fuses. No power to the socket of course either at the front of the truck just to rule out a burned out bulb. The light on the dash instrument panel does turn on though.

High beams work fine. MFS cable is good. I replaced the MFS after this problem occured and checked condition of all connectors - all good.

I unplugged the brake sensor relay just to check function. When I plugged it back it, I had brake lights so that problem is solved. The truck was shifting out of park. I checked to make sure it would not shift out of park when disconnected.

Grounds in the cab are all good. I only found one ground in the engine compartment near the vaccuum solenoids on the firewall. Any ideas on where to look for the others?

Starting to think my fuse box could be bad....or one of the connectors running into it could have something loose. Any thoughts on where to pickup a good wiring diagram?

 

How did you check the MFS connector to confirm it as good ?

did you try tilting the steering wheel all the way up ?

The MFS you installed, was it new ?

If the high beams work, and the low beams do not ( and no power to either side of the fuses for the L & R low beams ) that points to an issue with the MFS.

Brake relay sensor ?? What is this ?

If the brake pedal position switch had an issue, the shift interlock would not have allowed you to shift out of park while the truck was running.

The other ground lugs in the engine compartment are towards the front by the headlamps and by the washer fluid / battery area.

If you are not getting power to the fuses for the low beams, and the high beams work fine, these should be OK, but best to check them. Back out the screw, wire wheel the fender, and reinstall them.

Need some info on how you are ruling out the MFS before you go tearing into the fuse panel. If you had an issue with the low beams due to the connector on the fuse panel, the high beams should also have the same issue, unless the pins got pushed out.

 

I've tried moving the steering wheel up all the way - no luck. There seems to be enough slack in the wires.

When I replaced the MFS sensor (brand new out of the box from O'Reiley), I looked to make sure all of the pins were correctly seated in the plastic housing. I also checked to make sure none of the wires were loose in the connector. Is there a way you would reccomend to check this connector electrically? Maybe I missed something here.

Brake sensor relay is what I incorrectly called the sensor on the brake pedal which you correctly called the brake pedal position switch. Wasn't sure what the correct name was so I tried to make something descriptive up . I pulled it off, and could not shift out of park. Put it back on and could shift out of park and the brake lights were working again.

Any advice on testing the MFS connector before tearing into the fuse panel is appreciated.

 

You can pull the MFS, and directly jumper the circuits using the MFS test chart.

If these prove no good, you can follow the circuit to the next connector behind the knee panel, and test from there.

 

Good deal - this is very helpful and I will check today. I did disconnect the connector behind the kneewall when I replaced the GEM for will check that as well.

The hazard switch looks a bit tricky, but I should be able to rig something up.