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Home >> Chevrolet >> 1996 >> Corvette Base, 2D Convertible, 5.7 5 >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Central Control Module >> Diagnosing & Repairing CCM DTCS >> DTC 71, LCD Dimming Output Circuit Shorted To Battery Or CCM Internal Open >> Testing
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DTC 71, LCD Dimming Output Circuit Shorted To Battery Or CCM Internal Open: Testing

  1. Cover ambient light sensor on Driver Information Center (DIC) with dark tape to simulate darkness. Turn parking lights on and operate dimmer control. If instrument panel and cluster lighting does not dim and brighten with dimmer control, repair dimmer control. Go to next step after repairs. If instrument panel and cluster lighting dims and brightens with dimmer control, go to next step.
  2. Turn parking lights off. Turn ignition switch to OFF position. Remove radio control head and heater/air conditioning control head (if equipped). Disconnect connectors from both control heads. Connect a test light between radio control head harness connector terminal No. 3 and ground. Turn ignition switch to ON position. If test light illuminates, repair short to battery in LCD dim control circuit. If test light does not illuminate, go to next step.
  3. Turn ignition switch to OFF position. Connect a test light between radio control head harness connector terminal No. 3 and battery voltage. Turn parking lights on. Place dimmer control in full bright position. Note test light brightness. Move dimmer control through full range and observe test light. If test light brightness does not change as dimmer control is operated, go to step 6). If test light brightness changes as dimmer control is operated, go to next step.
  4. Clear DTCs. Reconnect radio control head connector. Operate dimmer control and check for DTC 71. If DTC 71 sets, replace radio control head. If DTC 71 does not set, reconnect heater/air conditioning control head connector. Operate dimmer control and check for DTC 71. If DTC 71 sets, replace heater/air conditioning control head. If DTC 71 does not set, go to next step.
  5. Check for poor connections at CCM, radio control head and heater/air conditioning control head. Poor connections could cause an open or an intermittent fault. If code is set as history, problem may be intermittent. Try to recreate fault while performing test by wiggling wiring and connectors. Check for poor connections at all connectors that may be causing intermittent condition.
  6. Using a test light, backprobe CCM Gray connector, terminal C2 to battery voltage. Turn parking lights on. Move dimmer control through full range and observe test light. If test light brightness does not change as dimmer control is operated, check for poor connections at CCM. If connections are okay, replace CCM. If test light brightness changes as dimmer control is operated, go to next step.
  7. No problem is present. Check for poor connections at CCM and radio control head and heater/air conditioning control head. Poor connections could cause an open or an intermittent fault. If code is set as history, problem may be intermittent. Try to recreate fault while performing test by wiggling wiring and connectors. Check for poor connections at all connectors that may be causing intermittent condition.
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