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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy P42 Commercial Chassis 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Brake Warning Indicator Always On

Brake Warning Indicator Always On P42

Step

Action

Value(s)

Yes

No

1

Turn the ignition to RUN.

Does the ABS lamp illuminate for a few seconds and then go off?

--

Go to Step 2

Go to Step 16

2
  1. Start the engine.
  2. Listen for an alarm.

Does the power brake alarm sound while the BRAKE lamp isilluminated?

--

Go to Step 15

Go to Step 3

3
  1. Turn the ignition to LOCK.
  2. Open the end of the diode network housing.
  3. Carefully remove the diode network circuit board from its connector.
  4. Turn the ignition to RUN and check the BRAKE lamp.

Is the BRAKE lamp illuminated?

--

Go to Step 4

Go to Step 7

4
  1. Turn the ignition to LOCK.
  2. Remove the connector from the instrument cluster.
  3. Turn the ignition to RUN.
  4. Use a test lamp from B+ to check for ground at terminal 28 of the connector.

Is this terminal shorted to ground?

--

Go to Step 6

Go to Step 5

5
  1. Turn the ignition to LOCK.
  2. Replace the instrument cluster.

Is the repair complete?

--

System OK

--

6
  1. Turn the ignition to LOCK.
  2. Examine the following areas for a short to ground or an electrical fault:
    3. • Between the instrument cluster terminal 28 and splice S205.
    • Between the diode network terminal H and splice S205.
    • Between the diode network terminal G and splice S205.
    • Between the diode network terminal F (if the vehicle has daytime running lamps) and splice S205.
    • Between splice S205 and the park brake switch.
    • Check for a faulty park brake switch.
  3. Repair the fault found.

Is the repair complete?

--

System OK

--

7

With the ignition in RUN, backprobe the diode network connector terminal A with a test lamp to B+.

Does the lamp illuminate?

--

Go to Step 15

Go to Step 8

8

With the ignition in RUN, backprobe the diode network connector terminal B with a test lamp to B+.

Does the lamp illuminate?

--

Go to Step 12

Go to Step 9

9

With the ignition in RUN, backprobe the diode network connector terminal C with a test lamp to B+.

Does the lamp illuminate?

--

Go to Step 11

Go to Step 10

10

Replace the diode network.

Is the repair complete?

--

System OK

--

11
  1. Locate the fault in circuit 1134 (LT BLU).
    2. • If the vehicle has DRL:
       • A short to ground between the diode network terminal C and splice S257.
       • A short to ground between splice S257 and the ignition switch terminal D of C2.
       • The ignition switch.
       • A short to ground between splice S257 and the DRL module terminal A.
       • The DRL module.
       • A short to ground between splice S257 and the park brake switch.
       • The park brake switch.
    • If the vehicle does not have DRL:
       • A short to ground between the diode network terminal C and the ignition switch terminal D of C2.
       • The ignition switch.
  2. Repair the fault found.

Is the repair complete?

--

System OK

--

12
  1. Turn the ignition LOCK.
  2. Replace the diode network into its connector and close the housing.
  3. Disconnect the connector from the brake pressure differential switch
  4. Turn the ignition to RUN

Is the BRAKE lamp illuminated?

--

Go to Step 13

Go to Step 14

13
  1. Perform a brake system diagnostic to find the leak or other source of the pressure differential.
  2. Repair and bleed the hydraulic system.
  3. Reset the pressure differential switch.

Is the repair complete?

--

System OK

--

14

Find and repair the short to ground in circuit 680 between the diode network, terminal B, and connector C1, terminal H of the EBCM, and the brake pressure differential switch, terminal A.

Is the repair complete?

--

System OK

--

15
  1. Turn the ignition to LOCK.
  2. Locate the fault in circuit 965.
    3. • If the vehicle is not equipped with an power brake alarm circuit, check for a short to ground in circuit 965 (YEL/BLK) between the diode network terminal A and connector C206 terminal A.
    • If the vehicle is equipped with an alarm circuit, check the following areas for a short to ground or a faulty component:
       • Circuit 965 (YEL/BLK) between the diode network terminal A and connector C206 terminal A.
       • Circuit 1651 (BLK/WHT) between connector C206 terminal A and the Park Brake Booster Fluid Flow Indicator/Alarm Delay Module terminal E.
       • Circuit 1651 (BLK/WHT) between the Park Brake Booster Fluid Flow Indicator/Alarm Delay Module terminal E and the Power Brake Booster Fluid Flow Alarm terminal A.
       • Circuit 966 (TAN) between the Park Brake Booster Fluid Flow Indicator/Alarm Delay Module terminal C and the Power Brake Booster Fluid Flow Indicator/Alarm Switch terminal B.
       • The Park Brake Booster Fluid Flow Indicator/Alarm Delay Module.
  3. Repair as needed.

Is the repair complete?

--

System OK

--

16

Check for ABS DTCs and repair as indicated.

Is the repair complete?

--

System OK

--

Brake Warning Indicator Always On P32 US/Canada

Step

Action

Value(s)

Yes

No

1

Turn the ignition to RUN.

Does the ABS lamp illuminate for a few seconds and then go off?

--

Go to Step 2

Go to Step 15

2
  1. Start the engine.
  2. Listen for an alarm.

Does the park brake alarm sound while the BRAKE lamp is on?

--

Go to Step 14

Go to Step 3

3
  1. Turn the ignition to LOCK.
  2. Open the end of the diode network housing.
  3. Carefully remove the diode network circuit board from its connector.
  4. Turn the ignition to RUN and check the BRAKE lamp.

Is the BRAKE lamp illuminated?

--

Go to Step 4

Go to Step 7

4
  1. Turn the ignition to LOCK.
  2. Remove the connector from the instrument cluster.
  3. Turn the ignition to RUN.
  4. Use a test lamp from B+ to check for ground at terminal 28 of the connector.

Is this terminal shorted to ground?

--

Go to Step 6

Go to Step 5

5
  1. Turn the ignition to LOCK.
  2. Replace the instrument cluster.

Is the repair complete?

--

System OK

--

6
  1. Turn the ignition to LOCK.
  2. Examine the following areas for a short to ground or an electrical fault:
    3. • Between the instrument cluster terminal 28 and splice S205.
    • Between the diode network terminal E and splice S205.
    • (US) Between splice S205 and the pull button relay or the park brake switch.
    • Check for a faulty park brake switch or pull button relay.
    • Between S205 and the park brake alarm relay (Auto Apply).
    • A faulty park brake alarm relay.
    • Between the diode network terminal D and splice S205 (Canada).
  3. Repair the fault found.

Is the repair complete?

--

System OK

--

7

With the ignition in RUN, backprobe the diode network connector terminal F with a test lamp to B+.

Does the lamp illuminate?

--

Go to Step 11

Go to Step 8

8

With the ignition in RUN, backprobe the diode network connector terminal A with a test lamp to B+.

Does the lamp illuminate?

--

Go to Step 10

Go to Step 9

9

Replace the diode network.

Is the repair complete?

--

System OK

--

10
  1. Locate the fault in circuit 1134 (LT BLU).
    2. • If the vehicle has DRL (Canada):
       • A short to ground between the diode network terminal C and splice S207.
       • A short to ground between splice S207 and the ignition switch terminal D of C2.
       • The ignition switch.
       • A short to ground between splice S207 and the DRL module terminal A.
       • The DRL module.
       • A short to ground between splice S207 and the park brake switch.
       • The park brake switch.
    • If the vehicle does not have DRL (US):
       • A short to ground between the diode network terminal C and the ignition switch terminal D of C2.
       • The ignition switch.
  2. Repair the fault found.

Is the repair complete?

--

System OK

--

11
  1. Turn the ignition LOCK.
  2. Replace the diode network into its connector and close the housing.
  3. Disconnect the connector from the brake pressure differential switch
  4. Turn the ignition to RUN

Is the BRAKE lamp illuminated?

--

Go to Step 13

Go to Step 12

12
  1. Perform a brake system diagnostic to find the leak or other source of the pressure differential.
  2. Repair and bleed the hydraulic system.
  3. Reset the pressure differential switch.

Is the repair complete?

--

System OK

--

13

Find and repair the short to ground in circuit 680 (PPL) between the diode network, terminal F, and the EBCM, connector C1, terminal H, and the brake pressure differential switch, terminal A.

Is the repair complete?

--

System OK

--

14
  1. Check for a short to ground in circuit 920 (ORN) between diode D201 and the park brake alarm or the park brake alarm relay.
  2. Check for a faulty park brake alarm relay.
  3. Repair as required.

Is the repair complete?

--

System OK

--

15

Check for ABS DTCs and repair as indicated.

Is the repair complete?

--

System OK

--

Brake Warning Indicator Always On P32 Export

Step

Action

Value(s)

Yes

No

1

Turn the ignition to RUN.

Does the ABS lamplight for a few seconds and then go off?

--

Go to Step 2

Go to Step 20

2
  1. Start the engine.
  2. Listen for an alarm.

Do you hear an alarm sounding while the BRAKE lamp isilluminated?

--

Go to Step 3

Go to Step 4

3

Move the transmission range selector from Park to Neutral.

Does the alarm stop sounding?

--

Go to Step 19

Go to Step 16

4
  1. Turn the ignition to LOCK.
  2. Open the end of the diode network housing.
  3. Carefully remove the diode network circuit board from its connector.
  4. Turn the ignition to RUN and check the BRAKE indicator.

Is the BRAKE lampilluminated?

--

Go to Step 5

Go to Step 8

5
  1. Turn the ignition to LOCK.
  2. Remove the connector from the instrument cluster.
  3. Turn the ignition to RUN.
  4. Use a test lamp from B+ to check for ground at terminal 28 of the connector.

Is this terminal shorted to ground?

--

Go to Step 7

Go to Step 6

6
  1. Turn the ignition to LOCK.
  2. Replace the instrument cluster.

Is the repair complete?

--

System OK

--

7
  1. Turn the ignition to LOCK.
  2. Examine the following areas for a short to ground or an electrical fault:
    3. • Between the instrument cluster terminal 28 and splice S205.
    • Between the diode network terminal H and splice S205.
    • Between the diode network terminal G and splice S205.
    • Between splice S205 and the pull button relay (or the park brake switch if not auto apply).
    • Check for a faulty pull button relay or park brake switch.
    • Check for an open in circuit 909 providing power to terminal A1 (85) of the pull button relay.
    • Between S205 and the park brake alarm and alarm relay
    • Check for a faulty park brake alarm relay.
    • Check for an open in circuit 639 providing power to the park brake alarm relay, terminal A1 (85).
  3. Repair the fault found.

Is the repair complete?

--

System OK

--

8

With the ignition in RUN, backprobe the diode network connector terminal A with a test lamp to B+.

Does the lamp light?

--

Go to Step 16

Go to Step 9

9

With the ignition in RUN, backprobe the diode network connector terminal B with a test lamp to B+.

Does the lamp light?

--

Go to Step 13

Go to Step 10

10

With the ignition in RUN, backprobe the diode network connector terminal C with a test lamp to B+.

Does the lamp light?

--

Go to Step 12

Go to Step 11

11

Replace the diode network.

Is the repair complete?

--

System OK

--

12
  1. Locate the fault in circuit 1134 (LT BLU).
    2. • If the vehicle has DRL:
       • A short to ground between the diode network terminal C and splice S257.
       • A short to ground between splice S257 and the ignition switch terminal D of C2.
       • The ignition switch.
       • A short to ground between splice S257 and the DRL module terminal A.
       • The DRL module.
       • A short to ground between splice S257 and the park brake switch.
       • The park brake switch.
    • If the vehicle does not have DRL:
       • A short to ground between the diode network terminal C and the ignition switch terminal D of C2.
       • The ignition switch.
  2. Repair the fault found.

Is the repair complete?

--

System OK

--

13
  1. Turn the ignition LOCK.
  2. Replace the diode network into its connector and close the housing.
  3. Disconnect the connector from the brake pressure differential switch
  4. Turn the ignition to RUN

Is the BRAKE lampilluminated?

--

Go to Step 14

Go to Step 15

14
  1. Perform a brake system diagnostic to find the leak or other source of the pressure differential.
  2. Repair and bleed the hydraulic system.
  3. Reset the pressure differential switch.

Is the repair complete?

--

System OK

--

15
  1. Find and repair the short to ground in circuit 680 (PPL) in one of the following areas:
    2. • Between the diode network, terminal B, and the brake pressure differential switch terminal A
    • Between the diode network, terminal B, and the EBCM, connector C1, terminal H
  2. Repair the problem found.

Is the repair complete?

--

System OK

--

16
  1. Turn the ignition to LOCK.
  2. Open the end of the diode network housing.
  3. Carefully remove the diode network circuit board from its connector.
  4. Turn the ignition to RUN and listen for the alarm.

Is the alarm sounding?

--

Go to Step 18

Go to Step 17

17
  1. Turn the ignition to LOCK.
  2. Locate the fault in circuit 965, the power brake booster fluid flow alarm circuit.
    3. • Check circuit 965 (YEL/BLK) for a short to ground in the following locations:
       • From the diode network terminal A to connector C200 terminal P9
       • From terminal P9 of connector C200 to splice S220
       • From splice S220 to the Power Brake Booster Fluid Flow Alarm terminal A
       •  From splice S220 to the Park Brake Booster Fluid Flow Indicator/Alarm Delay Module terminal E
    • Check circuit 966 (TAN) between the Park Brake Booster Fluid Flow Indicator/Alarm Delay Module terminal C and the Power Brake Booster Fluid Flow Indicator/Alarm Switch terminal B.
    • Check circuit 1928 from the Power Brake Booster Fluid Flow Indicator/Alarm Switch terminal A to the Power Brake Boost Pump Pressure Switch terminal A.
  3. Repair as needed.

Is the repair complete?

--

System OK

--

18
  1. Find and repair the short to ground in one of the following circuits:
    2. • Circuit 920 (ORN) between diode splice S203 and the park brake alarm relay terminal A2
    • Circuit 920 (ORN) between diode splice S203 and the park brake alarm
  2. Repair the problem found.

Is the repair complete?

--

System OK

--

19

Adjust or repair the parking brake system as required.

Is the repair complete?

--

System OK

--

20

Check for ABS DTCs and repair as indicated.

Is the repair complete?

--

System OK

--