LEMON Manuals: Even more car manuals for everyone
Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel System (Bi-Fuel & CNG) >> Alternative Fuel Pump Relay >> Diagnostic Procedure

Diagnostic Procedure

  1. Perform Alternative Fuels Diagnostic System Check - Engine Controls. See ALTERNATIVE FUELS DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing Alternative Fuels Diagnostic System Check - Engine Controls, go to next step.
  2. Select scan tool DTC display function for Alternative Fuels Engine Control Module (AF ECM). Does scan tool display DTC P1650? If yes, go to DTC P1650 under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article for diagnosis of electrical circuits. If no, go to next step.
  3. Turn ON the ignition with the engine OFF. With scan tool in Alternative Fuels - Special Function menu, command Fuel Pump ON. Listen for audible fuel pump operation. Can you hear fuel pump operate as commanded? If yes, go to next step. If no, go to step  5.
  4. Start and idle engine on CNG. Probe fuel pump Prime terminal using Test Light (J 34142-B) connected to ground. Is test light illuminated? If yes, go to step  10. If no, diagnose alternative fuel system. Go to FUEL SYSTEM DIAGNOSIS (BI-FUEL & CNG) .
  5. With scan tool in Alternative Fuels - Special Function menu, command Fuel Pump ON and OFF. Listen or feel for operation of Lock-Off Solenoid Relay. Does Lock-Off Solenoid Relay operate when fuel pump is commanded ON and OFF? If yes, go to next step. If no, diagnose fuel lock-off relay. Go to FUEL LOCK-OFF RELAY .
  6. With scan tool in Alternative Fuels - Special Function menu, command Fuel Pump ON and OFF. Listen or feel for operation of gasoline fuel pump relay. Does gasoline fuel pump relay operate when fuel pump is commanded ON and OFF? If yes, go to FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L)  under FUEL SYSTEM (GASOLINE). If no, go to next step.
  7. Disconnect AF fuel pump relay. Probe Fuel Pump Relay Control circuit terminal No. 30 with Test Light (J 34142-B) connected to ground. With scan tool in Alternative Fuels - Special Function menu, command Fuel Pump ON. Does test light illuminate when fuel pump is commanded ON? If yes, go to next step. If no, go to step  10.
  8. Connect AF fuel pump relay. Remove gasoline fuel pump relay. Probe gasoline fuel pump relay control terminal No. 85 using Test Light (J 34142-B) connected to ground. With scan tool in Alternative Fuels - Special Function menu, command Fuel Pump ON. Does test light illuminate when fuel pump is commanded ON? If yes, go to FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L)  under FUEL SYSTEM (GASOLINE). If no, go to next step.
  9. Test Fuel Pump Relay circuit between AF fuel pump relay and gasoline fuel pump relay for an open. Repair circuit as necessary. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  10. Repair Fuel Pump Relay Control circuit between AF fuel pump relay terminal No. 30 and circuit splice. After repairs, go to step  12.
  11. Replace AF Fuel Pump Relay. After repairs, go to next step.
  12. Remove all test equipment except scan tool. Connect any disconnected components, fuses, etc. With scan tool, clear DTC information from AF ECM and PCM. Turn the ignition OFF and wait 30 seconds. Start engine and operate vehicle. Observe MIL. Observe vehicle performance and driveability. After operating vehicle inspect BOTH control modules for stored DTCs. Does vehicle operate on CNG with normal driveability, no MIL illumination and no stored DTCs? If yes, system is okay. If no, perform Alternative Fuels Diagnostic System Check - Engine Controls. See ALTERNATIVE FUELS DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
scientia non olet · About LEMON Manuals