LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2001 >> Astro Van Cargo, RWD >> Repair and Diagnosis >> Electrical >> Charging Systems >> Diagnostic Tests >> DTC P1638: Pulse Width Modulated Signal Out Of Range

DTC P1638: Pulse Width Modulated Signal Out Of Range

  1. If engine electrical diagnostic system check was performed, go to next step. If engine electrical diagnostic system check was not performed, go to ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Connect scan tool to Data Link Connector (DLC). Start engine. Observe GEN F-TERMINAL parameter in PCM data list. If GEN F-TERMINAL parameter is 5-95 percent, go to next step. If GEN F-TERMINAL parameter is not 5-95 percent, go to step  5 .
  3. Using scan tool, command generator Off. Observe GEN F-TERMINAL parameter in PCM data list. If GEN F-TERMINAL parameter is zero percent, go to next step. If GEN F-TERMINAL parameter is zero percent, problem may be intermittent. Check wiring and connections, see PRELIMINARY INSPECTION  under TROUBLE SHOOTING.
  4. Turn ignition switch to OFF position. Disconnect generator 4-pin harness connector. Start engine. Using DVOM measure voltage between ground and generator turn-on signal circuit, generator harness connector terminal "B" (Brown wire). Using scan tool, command GEN-L terminal On and Off. With generator Off voltage reading should be 0 volts. With generator On, voltage reading should be 5 volts. If voltage reading is not as specified, go to next step. If voltage reading is as specified, go to step  6 .
  5. Turn ignition switch to RUN position. Using a test light connected to battery positive voltage, repeatedly probe generator field duty cycle signal circuit, generator harness connector "C" (Gray wire), while observing GENERATOR PWM on scan tool. If GENERATOR PWM display is affected, go to step  8 . If GENERATOR PWM display is not affected, go to step  7 .
  6. Test generator turn on signal circuit, generator harness connector "B" (Brown wire), for a short or an open. See WIRING DIAGRAMS  . If problem exists, repair circuit as necessary and go to step  11 . If no problem exists, go to step  9 .
  7. Test generator field duty cycle signal circuit, generator harness connector "C" (Gray wire), for a short or an open. See WIRING DIAGRAMS  . If problem exists, repair circuit as necessary and go to step  11 . If no problem exists, go to step  9 .
  8. Inspect generator harness connector for poor connections. If problem exists, repair circuit as necessary and go to step  11 . If no problem exists, go to TEST A: CHARGING SYSTEM TEST  under SYSTEM TESTS.
  9. Inspect PCM harness connectors for poor connections. If no problem exists, go to next step. If problem exists, repair circuit as necessary and go to step  11 .
  10. Replace PCM. After replacement, reprogram PCM. See POWERTRAIN CONTROL MODULE under REMOVAL & INSTALLATION in BODY CONTROL MODULES - ASTRO & SAFARI article in ACCESSORIES & EQUIPMENT. After repairs are made, go to next step.
  11. Review and record scan tool fail records data. Using scan tool, clear DTCs. Operate vehicle within Fail Records conditions as noted. Using scan tool, observe Specific DTC information for DTC P1638. If an tool indicates DTC P1638 passed this ignition, system is okay. If scan tool indicates DTC P1638 failed this ignition, go to step  2 .
scientia non olet · About LEMON Manuals