1990 Pontiac LeMans BaseFACTORY OEM SERVICE PROCEDURE

Chart C-4B Ignition System Check (Remote Coil-Sealed Module)

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Check 2 different spark plug wires to ensure an open is not present. 1A) If spark occurs with EST connector disconnected, pick-up coil output is too low for EST operation.
  2. A spark indicates problem is distributor cap or rotor.
  3. Normally there should be battery voltage at "C" and "+" terminals. Low voltage would indicate an open or a high resistance circuit from the distributor to the coil or ignition switch. If "C" terminal voltage was low but "+" is 10 volts or more, circuit from "C" terminal to ignition coil or ignition coil primary is open.
  4. Checks for a shorted module or grounded circuit from the ignition coil to the module. The distributor module should be turned off so normal voltage (12 volts) is present. If module is turned on, the voltage would be low, but above one volt. Failure of this test can cause ignition coil to fail due to excessive heat. With an open ignition coil primary winding, a small amount of voltage will leak through the module from the "+" terminal to tachometer terminal.
  5. Applying a voltage of 1.5-8 volts to module terminal "P" should turn module on and the tach terminal voltage will drop to 7-9 volts. This test determines if the module or coil is faulty, or if the pick-up coil is not generating the proper signal to turn module on. This test can be performed by using a DC battery of 1.5-8 volts. The use of the test light is to allow the "P" terminal to be probed more easily. Some digital multi-meters can be used to trigger the module by selecting ohms, usually the diode position. In this position the meter may have a voltage across it's terminals which can be used to trigger module.
  6. This should turn off the module and cause a spark. If no spark occurs, The fault is most likely in the ignition coil.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.