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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 59 (Automatic Transmission Diagnosis - 4L80-E) >> Diagnostic Tests >> DTC B2722: Transmission Preference Switch Circuit - Low Input >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet 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. Install a scan tool. Turn ignition on, engine off. Using scan tool, observe the TRANSMISSION PREFERENCE parameter. Activate the tow/haul switch. Does the TRANSMISSION PREFERENCE parameter change states (ON/OFF)? If so, see DIAGNOSTIC AIDS . If not, go to next step.
  3. Turn ignition off. Disconnect the tow/haul switch. Turn ignition on, engine off. Using scan tool, observe the TRANSMISSION PREFERENCE parameter. Does the scan tool display OFF? If so, go to step  6. If not, go to next step.
  4. Test the tow/haul switch signal circuit for a short to ground. Did you find and correct the condition? If so, go to step  9. If not, go to next step.
  5. Inspect for poor connections at the BCM. Did you find and correct the condition? If so, go to step  9. If not, go to step  7.
  6. Inspect for poor connections at the tow/haul switch. Did you find and correct the condition? If so, go to step  9. If not, go to step  8.
  7. Replace the BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. Did you complete the replacement? If so, go to step  9.
  8. Replace the tow/haul switch. See SHIFT LEVER REPLACEMENT - ON VEHICLE WITH TOW/HAUL SWITCH  Did you complete the replacement? If so, go to next step.
  9. Use the scan tool to clear the DTCs. Operate the vehicle within the conditions for running the DTC, as specified in the supporting text. Does the DTC reset? If so, go to step  1. If not, system is okay.
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