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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 393 (POWER TAKE-OFF SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESPOWER TAKE-OFF (PTO) DOES NOT ENGAGETEST DESCRIPTION

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Test Description

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION 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.

2: This step tests for an open fog lamp fuse.
3: This step tests for open cruise fuse.
4: This step tests the battery positive circuit for battery voltage.
5: This step tests the battery positive circuit for an open.
6: This step tests the PTO relay output circuit for an open.
7: This step tests the PTO ON signal circuit for battery voltage.
8: This step tests the PTO ON signal circuit for an open.
9: This step tests the cruise control set/coast switch signal circuit for battery voltage.
10: This step tests the PTO status circuit for an open.
11: This step tests the PTO switch and PTO unit ground circuits for an open.
12: This step tests the battery positive and PTO relay output circuits for a short to ground.
13: This step tests the ignition 3 circuit for a short to ground.
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.
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	Turn the ignition ON, with the engine OFF. Set the PTO switch to ON. 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	Set the parking brake. Start the engine. 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

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.