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 number(s) below refer to the step number(s) on the diagnostic table.
- 2: Lack of communication may be due to a partial or total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
- 3: The presence of DTCs indicates that the PCM or TAC has detected a fault.
- 4: The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
- 5: This step insures that the PTO options in the scan tool are set according to the upfitters recommendations.
Diagnostic System Check - Power Take-Off (PTO)
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Install a scan tool. Does the scan tool power up? |
Go to Step 2 | Go to Scan Tool Does Not Power Up |
| 2 |
|
Go to Step 3 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications |
| 3 | Select the display DTCs function on the scan tool. Does the scan tool display any PCM or ECM DTCs? |
Go to Step 4 | Go to Step 5 |
| 4 | Does the scan tool display any DTCs which begin with a "U"? | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | Go to Diagnostic Starting Point - Engine Controls or Diagnostic Starting Point - Cruise Control |
| 5 | View the PTO options on the scan tool to verify that the PTO settings are correct for the specific PTO application. Are the PTO settings correct? |
Go to Symptoms - Power Take-Off (PTO) | Go to Step 6 |
| 6 | Change the PTO options as needed. See upfitter specifications in the upfitter installation manual. Are the PTO options set correctly? |
Go to Symptoms - Power Take-Off (PTO) | - |