I changed the lamp for the service engine soon indicator. Now the lamp functions.

Shorted the ALDL.
Some codes do not make sense.

12 No distributor reference pulse (diagnostic test active)

13 Oxygen sensor circuit open or no activity. The O2 sensor was replaced 2 years ago and data stream monitored using a wire back probed into the harness connector for proper operation. I can monitor the signal again.

22 Throttle position sensor error (signal low). I had replaced this once already but last year. No change.

23 Intake air temp sensor error (low temp indicated) I replaced the sensor 2 weeks ago. - No change.

26 Quad Driver Module (QDM A) error. I suspect this the the engine cooling fan quad driver as it does not function. I had to install an analog fan control.

34 MAP sensor circuit error (signal low indicating high vacuum) This makes no sense as there is not a MAP on the LN3.

35 IAC problem or idle error. The IAC clearly functions as I can hear the air flow changing and see the idle speed changing. I had cleaned it anyway - no change.

A lot of issues there that could all be traced to wiring. I'd trace wiring.

Update. I checked the sensors for continuity and function. All are checked at the ECU connector.

The Oz sensor wiring is fine from the ECU to the sensor. With engine warm, the voltage ranges from 0.55v at idle to 0.8v at fast idle. The sensor responds quickly if the throttle is blipped.

The throttle position sensor (TPS) has proper continuity. However - sense wire voltage ranges from 5v at idle to 5.1v at WOT. Yes - the voltage increases with throttle. This is opposite from what I'm finding on the net for proper operation.

Manifold air temp (MAT) has proper continuity. Resistance is 2200 ohms at 80 degrees F.

I didn't attempt to determine the quad driver issue

I do not know why there is a MAP code when there is not a MAP on the LN3. I also do not understand the code for the IAC as it can be heard operating.
Thoughts?

Have you cleaned all the grounds?

I cleaned the grounds by the ignition module/alternator and added a 10gauge direct ground wire from those to the battery. I can try to find any others and ensure they are clean.

IAC might be operating audibly, but it is possible that its guts have gone bad and it isn't really doing anything or isn't doing the right thing.

It is functioning in that the changing air bleed can be heard as it opens and closes.

On a whim, I looked up your car at Rockauto. It shows a MAP sensor listed for your engine.

At the same time, a bad MAP sensor might contribute to a chronic rich condition.

Are you sure this thing doesn't have a MAP sensor?

. . . and then I found this thread: https://www.gmforum.com/pontiac-168/...v-valve-311927

I think this is the next place to look . . . after confirming that you really really don't have a MAP sensor.

I searched for information of a MAP sensor. I simply could not find one on the manifold. I looked at Rock Auto as they typically have a decent database. I called Oreilles autoparts as they had some tutorials. Oreille'* stated that there is not one used on my vehicle.

I spent Friday and Saturday really digging around on the manifold and back of the engine looking for wiring issues and any unknown ground wires. I did some rework of the primary chassis ground making certain that all was clean and tight.

A friend brought over his scanner but the OBD connector does not interface with the early connector. I showed him how I shorted it to get codes. Now it only displayed 12 and 22. i started it. Still very rich. Exhaust left black soot on the ground in just a few minutes.

There is a smaller ground location on the firewall that has a number of ground wires to it. Some may have been factory grounds that were relocated and others stuff a prior owner added. I corrected some loose terminals on wires. I cleaned the body contact and added a bonding ground wire over to the primary chassis ground. Started it again. Seemed to run slightly better. Vacuum was improved. I started out on a test drive but stopped at a friends home for a few minutes. Started again - vacuum was down slightly and it was not running as well. Did a test drive down the highway. Vacuum was still down. This has been rather a pattern of sorts. Runs better sometimes and then not as good again. It always starts fine. Has decent power. If I were to guess at things it seems the ignition timing is retarded and something if making the mix too rich.

I ordered another throttle position sensor, a crankshaft position sensor, and an oxygen sensor. I have not changed the crank sensor before. I did notice that the plastic shield that would normally prevent seeing the relationship of the crankshaft position sensor and the harmonic balancer reluctor vanes is missing.

This link I'm including provided the photo I've attached. I am not finding a similar group of grounds on my engine. There are a few under the ignition module. Possibly they were relocated to the ignition module at some time in the past?


https://forums.aaca.org/topic/279456-additional-ground/