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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 44414
Experience:  16 years experience
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Trying to find a solution parking brake light staying on.

Customer Question

Trying to find a solution for the parking brake light staying on. 2002 Ford F 350 Diesel. Brake light chimes when moving. Caused by the sensor in the rear axel to indicate movement. The Parking Brake light stays on all the time. Have verified the brake pedal switch works. Have bypassed the vac switch and the brake fluid switch with no success. Also at the same time the light came on the turn signals quit working. Very strange because I can't find anywhere the two are related.
Submitted: 1 year ago.
Category: Ford
Expert:  Eric replied 1 year ago.

HI,

I am sorry that you have not been helped yet. I just came online and saw your question

I may be mistaken but the sensor in the rear differential is the abs speed sensor and if it is faulty, it will turn on the abs warning light.

I need to get the 17 digit vin number to pull the wiring schematics to be able to help you

Customer: replied 1 year ago.
Eric, Vin is 1FSW31F32EC77081. The reason I mentioned the sensor is that the chiming won't start unless the vehicle actually moves. The Parking brake light is on all the time. As soon as you move that stupid chime beeps exactly 50 times before it shuts off. I am making an assumption that the rear diff sensor is tied to the affected circuit to indicate movement with the parking brake still engaged, which it is not.
John
Expert:  Eric replied 1 year ago.

HI,

we are missing a digit from the vin - you have 16 and it should be 17 digits

Customer: replied 1 year ago.
Vin Number 1FTSW31F32EC77081
Expert:  Eric replied 1 year ago.

HI,

As I believed, the rear diff sensor is solely for the abs and for speedometer as well.

This is due to either a faulty parking brake applied(pba) switch, or break in the wire to it. It is located at top of the parking brake pedal assembly(see attached)

Customer: replied 1 year ago.
Not the switch. That was the most obvious problem and we checked that. We also thought that the wire may be shorted but could not find any issues. Unlikely that it would be shorted to ground in side the wiring harness. That also does not explain the turn signals not functioning at the same time.
Expert:  Eric replied 1 year ago.

HI,

Ok, you didnt mention that you had checked that switch, only that you checked the brake pedal switch which is not the same as the parking brake applied switch.

Not sure what else would cause it so I will opt out and see if another expert can help

Expert:  Chris (aka- Moose) replied 1 year ago.

Welcome, I'm Chris and independent contractor that helps customers here.

Would you like me to try and help on this issue your having?

Are you capable of removing the instrument cluster and doing some wire testing?

Thanks for letting me assist you. I hope I met all your expectations.

Please make sure to complete the required rating when ready so I am compensated by the website from the site and question fees you have already been charged. If your not able to rate my response, let me know why, so I can help more, and stay in contact with you.

Customer: replied 1 year ago.
I can remove the instrument cluster and can do most any testing.
Expert:  Chris (aka- Moose) replied 1 year ago.

Super, open the link below.

https://dl.dropboxusercontent.com/u/90220402/Pin11.png

I need you to remove the cluster, and unplug connector B. Now OHM test pin 11 light green/red to ground. You should get an open circuit, is that the result you get?

Customer: replied 1 year ago.
Chris,
Sorry for the delay. Ohmed the wire. results - Closed with parking brake pedal depressed. Open with parking brake pedal released with 87 Ohms.
Expert:  Chris (aka- Moose) replied 1 year ago.

Thanks, ***** ***** have preferred to see OL reading with it released. I am wondering if that small amount of continuity is enough to trigger the audible warning the light. Can you remove this wire and pin from the connector, plug the cluster back up and test it.

Customer: replied 1 year ago.
Ohms with pedal released was .4 Tested as you asked. Parking brake light out as expected. Still no turn signals or Daytime running lights. Would also assume the cruise is still not working. All of these quit at the same time. The beeping is now gone when in motion.
Expert:  Chris (aka- Moose) replied 1 year ago.

So with the wire removed the parking light and audible alarm are gone. unplug the parking brake switch, if the ohms now drop to zero, then the switch is bad. If they remain giving a reading then the wire is damaged.

Can you do the diag steps below for no turn signals?

https://dl.dropboxusercontent.com/u/90220402/02turn.pdf

Customer: replied 1 year ago.
Tested switch by itself , it functions correctly. Tested wire and no change. Still had 89 Ohms. But that wire does not go directly to the switch because it has to be inter-tied to the daytime running lights and the rear diff sensor and possibly the cruise control because they are all affected by the parking brake switch. So it stands to reason that there should be some resistance to grd on that wire. There is no resistance from end to end on the wire. We will take a look at the turn signal system but I think that may be related because it all quit at the same time.
Expert:  Chris (aka- Moose) replied 1 year ago.

The parking brake wire goes to the:

parking brake switch

instrument cluster

PCM

park brake relay

We need to unplug each and see if you can find what is causing this wire to have continuity to ground.

Customer: replied 1 year ago.
Ok Found a relay that when pulled clears short. Relay is under hood on driver side near hinge. I believe it is for the daytime running lights. There are three boxes with three relays each. have swapped relays and no change. Did find the same wire going to the flasher relay. Was going to replace flasher but autoparts did not have correct one.
Expert:  Chris (aka- Moose) replied 1 year ago.

When you pulled this relay did the parking brake light go out, no more audible tone and the cruise control now works?

Just no DRL operation?

View the link below, was it the park brake relay you removed?

https://dl.dropboxusercontent.com/u/90220402/PBR.pdf

Customer: replied 1 year ago.
Didn't test cruise control but the park brake light did go out. No DRL. Yes, it looks like we pulled the park brake relay.
Expert:  Chris (aka- Moose) replied 1 year ago.

Did I understand right you replaced this relay and the continuity you had prior remained?

Can you test the cruise?

Your next option is, I can help you bypass this relay or we can do much more wire testing.