1995 Buick Lesabre trouble codes 321 & 361

I borrowed a friend's Snap-on 2500 and these are the trouble codes it showed:

321 NO 18x Ignition pulses
361 EST line not Toggling

I cleared the codes out twice, but they came back. Also, the check engine light will not stay on permanently but the codes are still in memory. The car runs fine and there has been no decrease in fuel mileage. Is this an indication that some sensor or module is near the end of its lifespan? Any help would be appreciated. Thank you.

This could be either the ICM, or the CKPS. Replace the CKPS and have the ICM tested if the CKPS does not correct the problem.

HotZ28 thank you for response. Not to put the cart before the horse, but how does one go about testing the ICM?

Take it to Advance, O'Reilly's, or Auto Zone for testing, although not 100% accurate, it's a free service they offer to customers. Have you checked for corrosion on the battery terminals? (Common problem with side post terminals)

Take it to Advance, O'Reilly's, or Auto Zone for testing, although not 100% accurate, it's a free service they offer to customers.

Thats true Bo. The problem is the bench test doesn't effectively test the EST circuits. IC and Bypass mode for ignition timing. It sounds like the crank position sensor is the best starting point. I think the OP is looking for a CKPS replacement procedure for the VIN "L" 3800 engine.

Unless the OP has the tools & equipment necessary to change the CKPS, it may be better to to take it to an experienced shop that can do it for him. It should not be more than an 1-hr job at any shop that knows the procedure.