J71 Pump does not run / Parking brake will not release

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1995-2004 P32 Chassis J71 Parking Brake does not release.

Symptom

When I start my coach and place it into drive, with the yellow button on the dash pressed in, my parking brake does not release (My coach does not go anywhere, like it is not in gear).

Component locations

1995-2000 Pump Assembly

96-00_Labled_Actuator_US22.png

 

2001-2003 Pump Assembly

01-03-Pump_Assembly.png

 

2004 Pump Assembly

04_P32_J71_Pump_Loc_sm.png

Diagnostic Steps

Does the pump operate?

  • Find out...

Section 1

Chock your wheels.

  1. Turn your ignition key to the run position (do not start the coach).
  2. Press the yellow button on the dash "In".
  3. Place the coach into drive.

Do you hear the parking brake pump motor run?

  • No. Go to section 2
  • Yes. But the pump does not stop running. Go to this help article.

Section 2

Leave the coach in the state it is in (See section 1-1.2.3.), and get a test light.

  1. Connect the test light across your battery and make sure it lights.
  2. Go to the pump motor, using your test light with it grounded, unplug the pump motor plug and probe terminal A.
  • Does it light your test light?
    • Yes. Your pump motor has failed. Solution: Replace the pump motor or pump assembly.
    • No. Go to Section 3.

Section 3

Leave the coach in the state it is in (See section 1-1.2.3.), and get a test light.

  1. Locate the pump motor relay.
  2. With your test light grounded, probe the two large wires at the relay.
  • Does it light your test light on both wires?
    • Yes. You have a break in the wire between the pump motor relay and the pump motor. Solution: Repair the wire between the pump motor and relay.
    • No. Go to section 4.

Section 4 

Leave the coach in the state it is in (See section 1-1.2.3.), and get a test light.

  1. With your test light grounded, probe the two small wires on the pump motor relay.
  • Does one of the wires light your test light?
    • Yes. Test the small wire at the pump relay that does not light your test light for a good ground by connecting the "Clip" end of your test light to a known good 12v source and probing that wire.
      • Does that wire light your test light?
        • Yes. You have a failed pump motor relay. Solution: Replace the pump motor relay.
        • No. You have a bad ground to the pump motor relay. Solution: Repair the ground to the pump motor relay.
    •  No. Go to section 5.

Section 5

Leave the coach in the state it is in (See section 1-1.2.3.), and get a test light.

  1. Locate the pump motor pressure switch. (A.K.A. Rotten Green Switch, that could be black or brown also installed in the side of the pump assembly.)
  2. With your test light grounded, and the pump switch plugged in, back-probe both of the wires one at time.
  • How many wires light the test light?
    • One wire lights my test light. You have a failed pressure switch. Solution: Replace the pressure switch.
    • Two wires light my test light. You have a break in the wire between the pressure switch and the pump motor relay. Solution: Repair the break in the wire.
    • No wires light my test light. Go to Section 6.

Section 6

Leave the coach in the state it is in (See section 1-1.2.3.), and get a test light.

  1. Locate the parking brake fuse for your coach using the wiring diagram specific for your chassis model year. For example: Workhorse 2001-2004 it is fuse#11 under the dash it will be a 15 amp fuse.
  2. Test the fuse to see if it is blown.
  • Was the fuse blown?
    • Yes. The fuse was blown. Solution: Replace the fuse.

Here are some possible causes

  • Failed pump pressure switch or actuator pressure switch ( unplug these one at a time to see if the fuse still blows ).
  • Back up light bulb ( Remove them and see if the fuse still blows ).
  • Park neutral position switch on side of transmission ( Replace this last and see if the fuse still blows ).
  • Park neutral position switch relay ( Replace this and see if the fuse still blows )
  • Grounded positive wire in circuit ( Trace down wires to locate issue ).
    • No. The fuse was not blown. Go to section 7

Section 7

This section is a very general guide due to differences in model years.

For more specific information you will need to refer to your vehicle specific wiring diagram.

Leave the coach in the state it is in (See section 1-1.2.3.), and get a test light.

  1. Test the circuits according to the wiring diagram based on your chassis model year. See attachment for model years .
    • Generally the cure for this issue is the switch that tells the parking brake the coach is in gear. This switch is different based on the year of the coach. The early years up to about 1997 they use a cam and switch under the diver side floor board that stops working because the cam wears down enough that it is not pressing the switch any longer. We sell a kit to replace this arrangement Part# USP32SW. On the newer model years they use the park/neutral position switch to perform this function, this is located on the side of the transmission.
  2. Early model years: Locate the switch assembly under the floorboard by looking up between the steering gear and the inner fender with a flashlight. Follow the wires from the switch through the firewall with your eyes. Then open the hood and locate the plug that comes from the switch. Unplug that and jump across the plug with a wire, and see if the pump runs.
    • If the pump runs, then you need to install part#USP32SW.
    • If the pump does not run, make sure you have power to one of the wires. If you have gone through the diagnostic steps above and have power to one of the wires at the switch plug then you have a break in the wire that goes to the pump pressure switch. Solution: Repair the break in the wire.
  3. Late model years: Locate the park neutral switch on the driver side of the transmission.
    • Back probe the light green wire that goes into the plug C050 on the park neutral safety switch see image below. That wire should have 12v when the coach is in park with the key on. If it does then the switch is working. 
    • If you find the switch is functional, the issue will most likely be the push pull button or the push pull button relay. See you wiring diagram to further diagnose.C050.png
    • If you need to find a wiring schematic for your coach, you can find them listed here https://www.ultrarvproducts.com/Workhorse-Manuals

 

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