LEMON Manuals: Even more car manuals for everyone
Home >> Saturn >> 1993 >> SL1 Standard >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Basic Testing >> No Start Diagnosis (A-3) >> No Start - Engine Cranks Okay (3.1L & 3.4L PFI With Dis) >> Ignition System (3.1L Calif. "W" Body)

Ignition System (3.1L Calif. "W" Body)

  1. Disconnect tachometer wire (if equipped). A shorted tachometer or tachometer circuit will prevent vehicle from starting.
  2. Install scan tester. Check for stored ECM trouble codes. Scan TPS voltage. If TPS reading is greater than 2.5 volts, use Code 21 chart first. Scan RPM while cranking engine. If 3X RPM signal is displayed on scan tester, go to step 5). If RPM is not displayed, check for spark on 2 wires (2-4 or 4-6) using Spark Tester (ST-125). Check one wire at a time. Leave other wires connected to plugs while cranking. If spark occurs on both wires, go to next step. If no spark occurs on either wire, go to Code 82 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. If spark occurs on one wire only, go to step 4).
  3. Turn ignition off. Disconnect 6-wire ignition module connector. Turn ignition on. Monitor scanned RPM while momentarily touching RPM reference circuit wire (circuit No. 430) of ignition module harness connector with a test light connected to battery voltage. If RPM is indicated on scan tester, problem is faulty ignition module-to-harness connection or faulty ignition module. If RPM is not indicated, problem is open or short to ground in RPM reference circuit or faulty ECM.
  4. If spark occurs on one wire only, check pair of wires for plug that did not spark. Ensure each wire measures less than 30,000 ohms resistance. If wires are okay, switch coil assemblies. If problem moves with coil, replace faulty coil. If problem does not follow coil, ignition module is faulty.
  5. Scan fuel pump signal (PPSW) during cranking. If voltage is not indicated, see Code 54 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. If voltage is indicated, check fuel system pressure. See BASIC FUEL SYSTEM CHECKS. If fuel pressure is within specification, go to next step.
  6. Disconnect No. 1 or 6 injector harness connector. Turn ignition on. With test light connected to ground, probe Pink/Black wires of injector harness connectors. See Fig 1 . If light is not on, repair open in injector power supply wire.
  7. If test light is on, disconnect Black 8-pin ECM mini-harness connector. Using a Tech 1 scan tester in INJECTOR BALANCE mode and a test light connected to battery voltage, probe terminals "A", "B", "C", "E", "F" and "G" on ECM side of harness while cycling corresponding injector. If test light comes on for each injector, go to step 9).
  8. If test light does not come on, repair open in circuit that did not light or check for poor ECM connection. If wiring and connections are okay, replace ECM.
  9. Turn ignition on with engine off. With test light connected to ground, probe Black 8-pin ECM mini-harness connector terminals "A", "B", "C", "E", "F" and "G" on injector side of harness. If test light lights for each terminal, go to next step. If test light does not light for each terminal, repair open in circuit that did not light.
  10. Check resistance of individual injectors. Resistance should be 11.8-12.6 ohms at room temperature. Replace any injector that is not within specification.
Fig 1: 3.1L Calif. PFI Ignition System ("W" Body)
G93H39393Courtesy of GENERAL MOTORS CORP.
scientia non olet · About LEMON Manuals