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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 25, Courtesy Light Relay Coil Circuit Open Or Shorted To Ground >> Testing
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DTC 25, Courtesy Light Relay Coil Circuit Open Or Shorted To Ground: Testing

  1. Check LCD fuse No. 38 located in instrument panel fuse block, in right side of dash (accessible with door open). If fuse is blown, repair short to ground in courtesy light LCD fuse circuit. If fuse is okay, go to next step.
  2. Turn ignition switch to OFF position. Remove courtesy light relay. Connect a test light between courtesy light relay connector terminal E2 and ground. Turn ignition switch to ON position. If test light does not illuminate, repair poor connection or open in courtesy light LCD fuse circuit. If test light illuminates, go to next step.
  3. Using DVOM, measure resistance between courtesy light relay terminals E2 and E1. If resistance is not 50-80 ohms, replace relay and go to next step. If resistance is 50-80 ohms, go to next step.
  4. Using DVOM, check for continuity between courtesy light relay terminals E5 and E1. If continuity is present, replace relay and go to next step. If continuity is not present, go to next step.
  5. Connect a test light between courtesy light relay connector terminals E1 and E2. Connect a jumper wire between Data Link Connector (DLC) terminals No. 12 and 5. Turn ignition switch to ON position. Press TRIP/ODO (next test) button on DIC until "1.4" displays on trip monitor. Press ENG/MET (next value) button on DIC until "10...0" displays on trip monitor. Display will cycle between "10...0" (off) and "10...1" (on). If test light is constantly illuminated, repair short to ground in courtesy light control circuit. If test light illuminates when "10...1" is displayed, go to next step. If test light does not illuminate when "10...1" is displayed, go to step 7).
  6. No problem is present. 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. When a short to ground is present in courtesy light control circuit, courtesy lights will be constantly illuminated. When an open is present in courtesy light control circuit, courtesy lights will not illuminate.
  7. Using a test light connected to courtesy light relay connector terminal E2, backprobe CCM Green connector, terminal D12. Connect a jumper wire between Data Link Connector (DLC) terminals No. 12 and 5. Turn ignition switch to ON position. Press TRIP/ODO (next test) button on DIC until "1.4" displays on trip monitor. Press ENG/MET (next value) button on DIC until "10...0" displays on trip monitor. Display will cycle between "10...0" (off) and "10...1" (on). If test light illuminates when "10...1" is displayed, repair open in courtesy light control circuit. If test light does not illuminate when "10...1" is displayed, check for poor connections at CCM. If connections are okay, replace CCM.
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