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Makes 🢒 Chevrolet 🢒 2000 🢒 Chevy P12 Chassis 🢒 Brakes 🢒 Park Brake 🢒 Hydraulic Park Brake Diagnostic

Hydraulic Park Brake Diagnostic Inoperative/Does Not Release

Park Brake Does Not Release

Step

Action

Value(s)

Yes

No

1
  1. Set the TR selector in Park (P).
  2. Make sure that the Pull Button Switch is IN (Not Applied).
  3. Turn the ignition switch to RUN.

Does the AUTO PARK indicator lamp light and stay on?

--

Go to Step 7

Go to Step 2

2
  1. Turn the ignition switch to LOCK.
  2. Remove the cover from the Underhood Fuse-Relay Center.
  3. Check AUTO PARK Fuse 34.

Is Fuse 34 blown?

--

Go to Step 4

Go to Step 3

3

Repair the open in Circuit 639 (PNK) between AUTO PARK Fuse 34 and splice S111.

Is the repair complete?

--

System OK

--

4
  1. Replace AUTO PARK Fuse 34.
  2. Turn the ignition switch to RUN.

Does the AUTO PARK indicator lamp light and stay on?

--

Go to Step 7

Go to Step 5

5
  1. Turn the ignition switch to LOCK.
  2. Check AUTO PARK Fuse 34.

Is Fuse 34 blown?

--

Go to Step 6

Go to Step 7

6
  1. Find and repair the short to ground in any of the following circuits:
    2. • Circuit 639 (PNK) between AUTO PARK Fuse 34 and splice S111
    • Circuit 639 (PNK) between S111 and the Park Brake Pressure Indicator Switch
    • Circuit 639 (PNK) between S111 and the Park Brake Pull Button Switch
    • Circuit 639 (PNK) between S203 and the Park Brake Alarm
    • Circuit 639 (PNK) between S111 and the Park Brake Position Switch Relay
    • Circuit 907 (LT BLU) from the Park Brake Pressure Indicator Switch to diode splice S308
    • Circuit 1844 (LT GRN) from diode splice S309 to splice S302
    • Circuit 1844 (LT GRN) from diode splice S307 to splice S302
    • Circuit 1844 (LT GRN) from splice S302 to Instrument cluster connector terminal 2
  2. Replace Fuse 34.

Is the repair complete?

--

System OK

--

7

Move the TR selector to Neutral (N).

Does the AUTO PARK lamp go out after a few seconds?

--

Go to Step 8

Go to Step 9

8

Find and repair the mechanical problem in the park brake auto apply system.

Is the repair complete?

--

System OK

--

9
  1. Return the TR selector to Park (P).
  2. Have an assistant get positioned near the park brake pump mechanism and listen for the sound of the hydraulic pump running.
  3. Move the TR selector to Neutral.

Could the assistant hear the pump run?

--

Go to Step 10

Go to 17

10
  1. Examine the park brake hydraulic system for a leak.
  2. Check the reservoir to see that it has hydraulic fluid.

Is there a problem with the hydraulic system?

--

Go to Step 11

Go to Step 12

11

Repair the hydraulic system or replenish the reservoir as required.

Is the repair complete?

--

System OK

--

12
  1. Unplug the pressure valve solenoid connector.
  2. Use a test lamp to probe connector terminal A (YEL/BLK) to ground.

Does the test light illuminate?

--

Go to Step 14

Go to Step 13

13

Repair the open in Circuit 1131 between splice S304 and the solenoid connector.

Is the repair complete?

--

System OK

--

14

Test for continuity between the harness solenoid connector terminal B (BLK) to ground.

Is the continuity good?

--

Go to Step 15

Go to Step 16

15

Replace the pressure valve solenoid.

Is the repair complete?

--

System OK

--

16

Repair the open in circuit 150 (BLK) between solenoid connector terminal B and splice S305.

Is the repair complete?

--

System OK

--

17
  1. Return the TR selector to Park.
  2. Turn the ignition to LOCK.
  3. Check AUTO PARK MaxiFuse 54 in the Engine Wiring Harness Junction Block (Underhood Fuse-Relay Center).

Is this fuse blown?

--

Go to Step 18

18
  1. Install a new 60 A MaxiFuse for AUTO PARK MaxiFuse 54.
  2. Remove this fuse and examine it.

Has this fuse blown?

--

Go to Step 19

Go to Step 20

19

Repair the short to ground in Circuit 742 (RED) between MaxiFuse 54 and terminal 30 of the Park Brake Pump Motor Relay.

Is the repair complete?

--

System OK

--

20
  1. Turn the ignition switch to RUN.
  2. Have an assistant listen near the park brake pump.
  3. Move the TR selector to Neutral.
  4. Return the TR selector to Park.

Did the pump operate?

--

Go to Step 21

Go to Step 22

21

Check the park brake relase operation.

Is the repair complete?

--

System OK

--

22

Use a test lamp to check for voltage at terminal 30 (RED) on the Park Brake Pump Motor Relay.

Does the test light illuminate?

--

Go to Step 24

Go to Step 23

23

Repair the open in circuit 742 (RED) between AUTO PARK MaxiFuse 54 and Terminal 30 of the Park Brake Pump Motor Relay.

Is the repair complete?

--

System OK

--

24
  1. Move the TR selector to Neutral.
  2. Probe the relay socket terminal 87 (ORN) with a test lamp.

Does the test light illuminate?

--

Go to Step 25

Go to Step 30

25
  1. Return the TR selector to Park.
  2. Unplug the pump motor connector.
  3. Probe the connector terminal A (ORN) with a test lamp.
  4. Does the test light illuminate?

--

Go to Step 27

Go to Step 26

26

Repair the open in Circuit 1470 (ORN) between relay socket terminal 87 and Park Brake Pump Motor connector terminal A.

Is the repair complete?

--

System OK

--

27
  1. Return the TR selector to Park.
  2. Check continuity from connector terminal B (BLK) to ground.

Is the continuity good?

--

Go to Step 28

Go to Step 29

28

Replace the pump motor.

Is the repair complete?

--

System OK

--

29

Repair the open between connector terminal B (BLK) and ground G300.

Is the repair complete?

--

System OK

--

30

Probe the relay socket terminal 86 (PNK/BLK) with a test lamp.

Does the test light illuminate?

--

Go to Step 31

Go to Step 34

31
  1. Return the TR selector to Park.
  2. Remove the Park Brake Pump Motor Relay from its socket.
  3. Check continuity of circuit 150 (BLK) from relay socket terminal 85 to ground G300.

Is there continuity?

--

Go to Step 32

Go to Step 33

32

Replace the Park Brake Pump Motor Relay.

Is the repair complete?

--

System OK

--

33

Repair the open in circuit 150.

Is the repair complete?

--

System OK

--

34
  1. Unplug the connector from the Park Brake Pump Motor Switch.
  2. Probe connector terminal A (YEL/BLK) with a test lamp.

Does the test light illuminate?

--

Go to Step 35

Go to Step 36

35

Repair the open in Circuit 1929 (PNK/BLK) between the pump motor switch connector terminal B and the pump motor relay connector terminal 86, or replace the pump motor switch as required.

Is the repair complete?

--

System OK

--

36
  1. Reinstall the connector to the Park Brake Pump Motor Switch.
  2. Unplug inline connector C111.
  3. Use a test lamp to probe terminal E (YEL/BLK) on the engine harness (female) side of connector C111.

Does the test light illuminate?

--

Go to Step 38

Go to Step 37

37

Repair the open between C111, terminal E, and the Park Brake Pump Motor Switch connector terminal A.

Is the repair complete?

--

System OK

--

38
  1. Turn the ignition switch to LOCK.
  2. Reconnect connector C111.
  3. Repair the open in one of the following circuits:
    4. • Circuit 1131 (YEL/BLK)
    • The Park Switch in the TR selector
    • Circuit 909 (YEL)
    • The Park Brake Pull Button Switch
    • Circuit 639 between the Pull Button Switch terminal A and splice S111

Is the repair complete?

--

System OK

--

Hydraulic Park Brake Diagnostic Brake Motor Runs Constantly

Check the circuits for the following conditions:

    • A wire may be broken (or partially broken) inside the insulation. That could cause a system malfunction but appear good in a continuity test or a voltage check with a system disconnected. If possible, test the circuit for a voltage drop when the system is under load.
    • Examine any aftermarket electronic equipment for proper installation.

Park Brake Motor Runs Constantly

Step

Action

Value(s)

Yes

No

1
  1. Prepare the vehicle as follows:
    2. • Set the ignition switch to LOCK.
    • Set the TR control to Park.
  2. Check the park brake pump.

Is the pump running constantly?

--

Go to Step 2

Go to Step 7

2

Look at the instrument cluster.

Is the AUTO PARK light illuminated?

--

Go to Step 3

Go to Step 4

3

Repair the short to voltage in Circuit 1929 (PNK/BLK) between the park brake pump motor relay terminal 86, the park brake pump motor switch terminal B, and splice S306.

Is the repair complete?

--

System OK

--

4

Remove the park brake pump motor relay from its socket.

Does the motor stop running?

--

Go to Step 6

Go to Step 5

5

Repair the short to voltage in Circuit 1470 (ORN) between the park brake pump motor terminal A and the relay terminal 87.

Is the repair complete?

--

System OK

--

6

Replace the Park Brake Pump Motor Relay.

Is the repair complete?

--

System OK

--

7
  1. Turn the ignition switch to RUN.
  2. Keep the TR control in Park.

Is the motor running constantly?

--

Go to Step 8

Go to Step 11

8

Remove the park brake pump motor relay from its socket.

Does the motor stop running?

--

Go to Step 9

Go to Step 10

9

Repair the short to voltage in Circuit 1929 (PNK/BLK) between the park brake pump motor relay terminal 86, the park brake pump motor switch terminal B, and splice S308.

Is the repair complete?

--

System OK

--

10

Repair the short to voltage in Circuit 1470 (ORN) between the park brake pump motor terminal A and the relay terminal 87.

Is the repair complete?

--

System OK

--

11
  1. If the motor is pulsing on and off rapidly, and the AUTO PARK indicator is flickering, the problem is a shorted diode 899 between splices S306 and S307.
  2. Replace diode 899 with a new diode.

Is the repair complete?

--

System OK

--