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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Body and Accessories 🢒 Power Take-Off 🢒 Power Take-Off (PTO) Does Not Engage

Circuit Description

This symptom chart will aid in diagnosing a failed Power Take-Off (PTO) solenoid engagement. This diagnostic will not expose a mechanical problem with the PTO itself. Voltage is supplied at all times through the cruise fuse to the secondary side of the relay. When the relay is energized the contacts will close and current will be allowed to flow to the PTO solenoid. The solenoid has its own external ground. When the operator turns the ignition switch to RUN, voltage will be present at the PTO switch. When the PTO switch is turned to ON voltage will be present at the coil of the relay and at the PCM. If the PCM sees all of the conditions necessary to engage the solenoid, the PCM will ground the primary circuit of the relay.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests Engine Controls and Cruise Control for DTCs.

    2.

  2. This step tests for open fuses.

    3.

  3. This step tests the Power Distribution circuits.

    4.

  4. This step tests the PTO solenoid.

    5.

  5. This step tests for continuity on the ground circuit.

    6.

  6. This step tests for voltage at the Battery Positive Voltage and PTO On Switch-Signal circuits.

    7.

  7. This step tests the PCM and the PTO Engage Signal circuit.

    8.

  8. This step tests for continuity on the PTO Engage Signal circuit.

    9.

  9. This step ensures that all of the PCM conditions for engaging the PTO are met.

    10.

  10. This step tests for ground on the Battery Positive Voltage circuit.

    11.

  11. This step tests for a ground on the Battery Positive Voltage circuit.

    12.

  12. This step tests for ground on the PTO Supply-Voltage circuit.

    13.

  13. This step tests for ground on the Ignition 3 Voltage circuit.

    14.

  14. This step tests for ground on the Power Take-Off Switch Output Enable circuit.

    15.

  15. This step tests for voltage at the Ignition 3 Voltage circuit.

    16.

  16. This step tests the PTO Relay.

Step

Action

Yes

No

Schematic Reference: Power Take-Off (PTO) Schematics

1

Did you review the Power Take-Off Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Power Take-Off (PTO) Description and Operation

2

Did you perform a Diagnostic System Check?

Go to Step 3

Go to Diagnostic System Check - Power Take-Off (PTO)

3

Inspect the Fog Lamp and Cruise fuses.

Is either fuse open?

Go to Step 11

Go to Step 4

4

  1. Turn the ignition switch to RUN.
  2. With a test lamp test for voltage to the Fog Lamp and Cruise fuses.

Does the test lamp light on both tests?

Go to Step 5

Go to Step 24

5

  1. Ensure that all of the PTO engage conditions are met. Refer to Power Take-Off (PTO) Description and Operation .
  2. Turn the PTO switch to ON.
  3. With a test lamp test for voltage on the PTO Supply-Voltage circuit at the PTO solenoid.

Does the test lamp light?

Go to Step 6

Go to Step 7

6

With a DMM test for continuity on the PTO solenoid ground circuit.

Do you have continuity?

Go to Step 29

Go to Step 25

7

  1. Turn the PTO and Ignition switch OFF.
  2. Disconnect the relay connector.
  3. Turn the ignition switch to RUN.
  4. Turn the PTO to ON.

    5. Using a test lamp test for voltage at the Battery Positive Voltage and PTO On Switch-Signal circuits.

Does the lamp light on both tests?

Go to Step 8

Go to Step 16

8

  1. Turn the PTO and ignition switch OFF.
  2. Connect the PTO relay.
  3. Turn the ignition switch to RUN.
  4. Turn the PTO switch to ON.
  5. Ensure that all PTO Engage conditions are met. Refer to Power Take-Off (PTO) Description and Operation .
  6. Using a jumper wire ground the PTO Control circuit at the relay.

Does the PTO solenoid engage?

Go to Step 9

Go to Step 19

9

Test for continuity on the PTO Control circuit.

Does the PTO Control circuit have continuity?

Go to Step 10

Go to Step 26

10

Ensure that all of the PCM conditions for engaging the PTO are met. Refer to Power Take-Off (PTO) Description and Operation .

Are all of the conditions met?

Go to Step 31

Go to Step 27

11

Is the Fog Lamp fuse open?

Go to Step 12

Go to Step 14

12

  1. Remove the Fog Lamp fuse.
  2. Disconnect the PTO relay.
  3. Using a DMM test for ground on the Battery Positive Voltage circuit at the relay connector.

Is the Battery Positive Voltage circuit grounded?

Go to Step 22

Go to Step 13

13

  1. Disconnect the PTO Solenoid connector.
  2. Using a DMM test for ground on the PTO Supply-Voltage circuit at the relay connector.

Is the PTO Supply-Voltage circuit grounded?

Go to Step 23

Go to Step 29

14

  1. Remove the Cruise fuse.
  2. Disconnect the PTO Switch.
  3. Using a DMM test for ground on the Ignition 3 Voltage circuit at the switch connector.

Is the Ignition 3 Voltage circuit grounded?

Go to Step 21

Go to Step 15

15
  1. Disconnect the PTO Relay.
  2. Using a DMM test for ground on the PTO On Switch-Signal circuit at the relay connector.

Is the PTO On Switch-Signal circuit grounded?

Go to Step 20

Go to Step 28

16

Do you have voltage on the Battery Positive Voltage circuit?

Go to Step 17

Go to Step 22

17

  1. Remove the PTO switch from the Instrument Panel but leave it connected to the harness.
  2. Using a fused jumper wire, jump from the Ignition 3 Voltage circuit to the PTO On Switch-Signal circuit at the switch.
  3. Using a test lamp test for voltage at the PTO On Switch-Signal circuit at the PTO relay connector.

Do you have voltage?

Go to Step 28

Go to Step 18

18

  1. Turn the ignition switch OFF.
  2. Turn the PTO switch OFF.
  3. Disconnect the PTO switch.
  4. Turn the ignition switch to RUN.
  5. Using a test lamp test for voltage at the Ignition 3 Voltage circuit at the switch connector.

Do you have voltage?

Go to Step 20

Go to Step 21

19

  1. Disconnect the PTO Relay.
  2. Using a fused jumper wire, jump from the Battery Positive Voltage circuit to the PTO Supply-Voltage circuit at the relay connector.

Does the PTO Solenoid engage?

Go to Step 30

Go to Step 23

20

Repair the PTO On Switch-Signal circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

21

Repair the Ignition 3 Voltage circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

22

Repair the Battery Positive Voltage circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

23

Repair the PTO Supply-Voltage circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

24

Repair the affected Power Distribution circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

25

Repair the Ground circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

26

Repair the PTO Control circuit for an open, short to ground or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

27

Repair the malfunctioning PTO support circuit.

Did you complete the repair?

Go to Step 32

--

28

Replace the PTO switch. Refer to Upfitter instructions.

Did you complete the repair?

Go to Step 32

--

29

Replace the PTO solenoid. Refer to Upfitter instructions.

Did you complete the repair?

Go to Step 32

--

30

Replace the PTO relay. Refer to Upfitter instructions.

Did you complete the repair?

Go to Step 32

--

31

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls.

Did you complete the repair?

Go to Step 32

--

32

Test drive the vehicle and operate the PTO system as described in the supporting text.

Does the symptom occur?

Go to Step 2

System OK