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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 989 (Power Take-Off System) >> Diagnostic Information and Procedures >> Power Take-Off (PTO) Does Not Engage >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  This step tests for an open fog lamp fuse.
  2. 3:  This step tests for open cruise fuse.
  3. 4:  This step tests the battery positive circuit for battery voltage.
  4. 5:  This step tests the battery positive circuit for an open.
  5. 6:  This step tests the PTO relay output circuit for an open.
  6. 7:  This step tests the PTO ON signal circuit for battery voltage.
  7. 8:  This step tests the PTO ON signal circuit for an open.
  8. 9:  This step tests the cruise control set/coast switch signal circuit for battery voltage.
  9. 10:  This step tests the PTO status circuit for an open.
  10. 11:  This step tests the PTO switch and PTO unit ground circuits for an open.
  11. 12:  This step tests the battery positive and PTO relay output circuits for a short to ground.
  12. 13:  This step tests the ignition 3 circuit for a short to ground.
  13. 14:  This step tests the cruise control ON switch signal, cruise control set/coast signal, PTO status, and PTO ON signal circuits for a short to ground.
  14. 15:  This step tests the control side of the PTO relay for proper operation.
Power Take-Off (PTO) Does Not Engage

Step Action Yes No
Schematic Reference:  Power Take-Off (PTO) Schematics  
1 Did you perform a Diagnostic System Check - Power Take-Off? Go to Step 2  Go to Diagnostic System Check - Power Take-Off (PTO) 
2  Inspect the fog lamp fuse for an open.
Refer to Circuit Protection - Fuses in Wiring Systems.
Is the fuse open?		 Go to Step 12  Go to Step 3 
3  Inspect the cruise fuse for an open.
Refer to Circuit Protection - Fuses in Wiring Systems.
Is the fuse open?		 Go to Step 13  Go to Step 4 
4  Using a DMM, test the battery positive voltage circuit for voltage.
Does the DMM indicate battery voltage?		 Go to Step 7  Go toStep 5 
5  Using a DMM, test the battery positive circuit for an open or high resistance.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 6 
6  Using a DMM, test the PTO relay output circuit for an open or high resistance.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 7 
7 
  1. Turn the ignition ON, with the engine OFF.
  2. Set the PTO switch to ON.
  3. Using a DMM at the PTO relay, test for voltage on the PTO ON signal circuit.
Does the DMM indicate battery voltage?		 Go to Step 9  Go to Step 8 
8  Using a DMM, test the PTO ON signal circuit for an open or high resistance.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 9 
9 
  1. Set the parking brake.
  2. Start the engine.
  3. While pressing the PTO set switch, use a DMM to test for voltage on the cruise control set/coast switch signal circuit at the PTO unit.
Does the DMM indicate battery voltage?		 Go to Step 15  Go to Step 10 
10  Using a DMM, test the PTO status circuit for an open or high resistance.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 11 
11  Using a DMM, test the PTO switch and PTO unit ground circuits for an open or high resistance.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 17 
12  Using a DMM, test the battery positive and PTO relay output circuits for a short to ground.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 18 
13  Using a DMM, test the ignition 3 voltage circuit for a short to ground.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Step 14 
14  Using a DMM, test the cruise control ON switch signal, cruise control set/coast signal, PTO status, and the PTO ON signal circuit for a short to ground.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 19  Go to Inducing Intermittent Fault Conditions in Wiring Systems
15  With the PTO ON, use a fused jumper wire to ground the PTO control circuit.
Does the PTO relay turn ON?		 Go to Step 16  Go to Step 18 
16 Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 8.1L or Engine Control Module (ECM) Replacement in Engine Controls - 6.6L.
Did you complete the repair?		 Go to Step 19  -
17 Replace the PTO switch.
Refer to Power Take-Off (PTO) Switch Replacement .
Did you complete the repair?		 Go to Step 19  -
18 Replace the PTO relay.
Refer to Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) in Wiring Systems.
Did you complete the repair?		 Go to Step 19  -
19 Operate the PTO system as described in the supporting text.
Does the symptom occur?		 Go to Step 2  System OK
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