Power Take-Off: Diagnosis Chevrolet Silverado 2500

Visual/Physical Inspection

1. Inspect the easily accessible and visible system components for obvious damage or conditions which could cause the symptom.
2. Inspect the transmission for the proper transmission fluid level.
3. Inspect the hydraulic reservoir for the proper hydraulic fluid level.
4. Inspect the upfitter connections at the transmission.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. See «Power Take-Off (PTO) Does Not Engage»(ref-176719-S28945639082005051700000) .
2. See «Engine RPM Does Not Increase with Power Take-Off Engaged»(ref-176719-S36052362362005051700000) .
3. See «Power Take-Off (PTO) Indicator Inoperative»(ref-176719-S42278331752005051700000) .

1. Inspect the upfitter connections of the PTO system. Refer to «CHECKING AFTERMARKET ACCESSORIES»(ref-175672-S27030348872005042500000) .
2. Inspect the easily accessible, or the visible system components for obvious damage or conditions which could cause the symptom.
3. Inspect the transmission and the hydraulic pump for the proper fluid level.

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. See «Power Take-Off (PTO) Does Not Engage»(ref-176719-S28945639082005051700000) .
2. See «Engine RPM Does Not Increase with Power Take-Off Engaged»(ref-176719-S36052362362005051700000) .
3. See «Power Take-Off (PTO) Indicator Inoperative»(ref-176719-S42278331752005051700000) .

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 in 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.

When the Power Take-Off (PTO) switch is turned to the ON position and all PTO engage conditions are met, the engine RPM should increase to the are met, the engine RPM should increase to the standby speed. When the Power Train Control Module (PCM) receives the signal from the PTO switch the PCM will send a signal to the Throttle Actuator Control Module (TAC). The TAC module controls the TAC motor which changes the position of the throttle. Communications between the two modules is monitored and checked for accuracy by the PCM. DTCs may be recorded in the event of the failure. The 6.6L diesel engine does not have a TAC system and the engine RPM is strictly controlled by the ECM and the Fuel Injection Control Module.

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 3 Voltage circuit. When the PTO switch is turned to ON, the LED will illuminate. The indicator has its own ground circuit. The LED and PTO solenoid have different ground circuits. Therefore, the LED may be illuminated when the PTO solenoid is disengaged.