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· Premium Member
5,082 Posts
Discussion Starter · #1 ·
I have a friend with a '92 LT1, and I'm trying to give him some long distance support.

Here's what I know:

I am getting a code 16 Low Resolution Pulse not being read and I think it is the Opti. I am going to change it out this weekend. I checked the manual and the computer is sending the voltage to the pigtail (red/black wire A) properly. The car has a broken clip on the connector but it cuts off when it is just sitting there. I thought it might be hitting a bump and knocking it loose. It also cut off when I moved the tach filter that connects to the coil. Have you known anyone who has had this problem and fixed it?
Here's what I told him to try:

The Code 16 is indeed the Low Resolution pulse. Fundamentally, the Low Resolution pulse tells the ECM which cylinder is ready for fuel injection pulsing and ignition firing.

To troubleshoot, here's the quick and dirty thing to do.

Check the wiring connections, especially the pigtail connector from the Optispark to the main wiring harness. This is the black/red wire that goes to terminal "A" on the pigtail connector. On the 1992-93 ecm, this is wire C5 (green connector). If the wiring checks out (which you've indicated it does), you will have to replace the optical sensor module in the distributor.

I'm disturbed by the broken clip, as that may have allowed just enough corrosion over time to interfere with a good signal. These signals are typically low voltage/low current, so corrosion and intermittent connections can be an issue.
Did I overlook anything obvious? Anything else we can recommend that he take a look at?


· Registered
410 Posts
Hey, I have rarely seen codes on the Opti, and I have changed quite a few. Where is your friend at?
If the wiring checks out, get a new Opti. Not a cap and rotor. If you have to do the cap and rotor, seal it up real well and loctite the bolts that hold the rotor on.If possible upgrade to a 95 style so you can get a vented style, or get the tubing and make yours vented, well your friends.
I got tired of replacing them and ended up using a DELTEQ. Granted I run a little higher RPM than factory, up to 6500rpm. The Opti in the 92 isnt difficult to replace, just time consuming, if your first time. The water pump has 6 bolts, not four like most GM's.
While there, replace plug wires and plugs, and do one wire at a time using DIELECTRIC grease on the connectors to the Opti. Do not force the Opti on and make sure you align the splines going back in.
While replacing the OPTI replace the water pump, as it is probably getting ready to poop out too.

· DC Crew
2,929 Posts
I will save you some time on this one. Just do this simple test.

1. start car, leave in neutral
2. floor the gas quickly

If the optispark is bad, it will go flat for a few seconds, stumble and then start to pick back up. Good luck. :thumbsup:

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