GM Service Manual Online
For 1990-2009 cars only

Circuit Description

This symptom chart will aid in diagnosing a failed Power Take-Off (PTO) indicator. This diagnostic assumes that the PTO solenoid is functional and only the indicator is failing to come on. When the ignition switch is in RUN, voltage should be present on the Ignition 1 Voltage circuit. When the PTO switch is turned to ON, the LED will illuminate. The indicator has its own ground circuit. The PTO enable switch indicator and PTO solenoid have different ground circuits. Therefore, the indicator may be illuminated when the PTO solenoid is disengaged.

Test Description

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

  1. This step tests the PTO On switch signal circuit.

  2. This step tests the ground circuit.

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

Verify the fault is present.

Does the system operate normally?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Does the PTO solenoid engage?

Go to Step 4

Go to Power Take-Off (PTO) Does Not Engage

4

  1. Turn the ignition switch to RUN.
  2. Turn the PTO enable switch to ON.
  3. Ensure that the conditions for engaging the PTO solenoid are met. Refer to Power Take-Off (PTO) Description and Operation .
  4. Remove the PTO switch but leave it connected to the harness.
  5. Using a test lamp test for voltage at the PTO On Switch Signal circuit at the switch.

Does the test lamp illuminate?

Go to Step 5

Go to Step 6

5

  1. Turn the PTO enable switch to OFF
  2. Turn the ignition switch OFF.
  3. Disconnect the switch.
  4. Using a DMM test for continuity on the ground circuit at the switch connector.

Do you have continuity?

Go to Step 8

Go to Step 7

6

Repair the open or high resistance in both PTO On Switch Signal circuit. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 9

--

7

Repair the open or high resistance in the ground circuit. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 9

--

8

Replace the PTO Enable switch. Refer to Upfitters instructions.

Did you complete the replacement?

Go to Step 9

--

9

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

Does the symptom occur?

Go to Step 3

System OK