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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 214 (Automatic Transmission - ALLISON - Diagnosis) >> Diagnostic Tests >> DTC P1571: TCS PWM Circuit No Frequency (8.1L) >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Observe the Freeze Frame/Failure records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure records. If the DTC fails this ignition, proceed to next step. If the DTC passes this ignition, go to INTERMITTENTS in the appropriate FAULT ISOLATION article under ENGINE PERFORMANCE.
  3. Disconnect the PCM connector C1. Turn ON the ignition, with the engine OFF. Probe the requested torque signal circuit (CKT 463) of the PCM harness connector C1 pin 13 with a test lamp connected to battery voltage. If the test lamp illuminates, proceed to next step. If the test lamp does not illuminate, go to step  5.
  4. Turn OFF the engine. Disconnect the TCM connector C1. Turn ON the ignition, with the engine OFF. Probe the requested torque signal circuit (CKT 463) of the PCM harness connector C1 pin 13 with a test lamp connected to battery voltage. If the test lamp illuminates, go to step  11. If the test lamp does not illuminate, go to step  9.
  5. Probe the requested torque signal circuit (CKT 463) of the PCM harness connector C1 pin 13 with a DMM that is connected to a good ground. Observe the AC frequency on the DMM. If the frequency is more than 100 hz, proceed to the next step. If the frequency is less than 100 hz, go to  7.
  6. Disconnect the TCM connector C1. Probe the requested torque signal circuit (CKT 463) of the PCM harness connector C1 pin 13 with a test lamp connected to a good ground. If the test lamp illuminates, go to step  10. If the lamp does not illuminate, go to step  12.
  7. Test the requested torque signal circuit (CKT 463) for an open. If the correct condition was obtained, go to  14. If the correct condition was not obtained, proceed to the next step.
  8. Test for an intermittent and for a poor connection at the TCM. If the correct condition was obtained, go to  14. If the correct condition was not obtained, go to step  12.
  9. Test for an intermittent and for a poor connection at the PCM. If the correct condition was obtained, go to  14. If the correct condition was not obtained, go to step  13.
  10. Repair the short to voltage in the Requested Torque Signal circuit (CKT 463). When the repair is completed, go to step  14.
  11. Repair the short to ground in the Requested Torque Signal circuit (CKT 463). When the repair is completed, go to step  14.
  12. Replace the TCM. When the replacement is completed, go to step  14.
  13. Replace the PCM. When the replacement is completed, go to step  14.
  14. Observe the Freeze Frame/Failure records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Condition for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure records. If the DTC failed this ignition, go to step  2. If the DTC passed this ignition, proceed to the next step.
  15. Observe the Capture Info with a scan tool. If there any DTCs that have not been diagnosed, see the appropriate FAULT ISOLATION article in ENGINE PERFORMANCE. If there are no more DTCs, the system is okay.
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