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Home >> GMC >> 1998 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 22 (Transfer Case - Diagnosis - New Venture 246) >> DTC Tests >> DTC C0300: Rear Speed Sensor Malfunction >> Testing

DTC C0300: Rear Speed Sensor Malfunction: Testing

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1998 GMC Yukon, 1998 GMC Suburban, 1998 GMC Pickup, 1998 GMC Cab & Chassis, and 1998 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
  1. If ATC system check was performed, go to next step. If system check was not performed, see ATC SYSTEM CHECK  .
  2. Turn ignition off. Connect scan tool to DLC. Turn ignition to run position (engine off). Using scan tool, record all freeze frame and failure records. Turn ignition off. Disconnect rear drive shaft speed sensor and remove sensor from transfer case. Inspect sensor rotor for damage, misalignment or slipping on shaft. If problem is found, go to next step. If problem is not found, go to step 4)
  3. Repair or replace rear drive shaft speed sensor rotor as necessary. When repair is complete, go to step 15).
  4. Using a DVOM, measure resistance of speed sensor. If resistance is 1400-2700 ohms, go to step 6). If resistance is not 1400-2700 ohms, go to next step.
  5. Replace rear speed sensor. See REMOVAL & INSTALLATION  . When repair is complete, go to step 15).
  6. Turn ignition off. Disconnect ATC control module connectors C1 and C2. Connect self-powered test light between ground and Light Blue wire terminal of rear speed sensor connector. If test light is on, go to next step. If test light is off, go to step 8).
  7. Locate and repair short to ground in Light Blue wire circuit. When repair is complete, go to step 15).
  8. Connect self-powered test light between Light Blue and Dark Green wire terminals of rear speed sensor connector. If test light is on, go to next step. If test light is off, go to step 10).
  9. Locate and repair short between Light Blue wire and Dark Green wire. When repair is complete, go to step 15).
  10. Connect a jumper wire between ground and Light Blue wire terminal F5 at ATC control module connector C1. See WIRING DIAGRAMS  . Connect self-powered test light between ground and Light Blue wire terminal at rear speed sensor connector. If test light is on, go to step 12). If test light is off, go to next step.
  11. Locate and repair open in Light Blue wire circuit between ATC control module and rear speed sensor connectors. When repair is complete, go to step 15).
  12. Connect a jumper wire between ground and Dark Green wire terminal F6 at ATC control module connector C1. See WIRING DIAGRAMS  . Connect self-powered test light between ground and Dark Green wire terminal at rear speed sensor connector. If test light is on, go to step 14). If test light is off, go to next step.
  13. Locate and repair open in Dark Green wire circuit between ATC control module and rear speed sensor connectors. When repair is complete, go to step 15).
  14. Replace ATC control module. See REMOVAL & INSTALLATION  . When replacement is complete, go to next step.
  15. Turn ignition off. Reconnect all disconnected components. Road test vehicle in AUTO mode. Using scan tool, select "Specific DTC" and enter DTC C0300. If test runs and passes, system is functioning properly. If test does not run and pass, repeat test from step 1).
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