What was the exact numerical code for “low resolution too few pulses”?

 

p1371

 

That code doesn't mean "too few" low resolution pulses. It means there were NO low res pulses detected, while the PCM was detecting a predetermined number of high res pulses. The 96 factory manual does not mention the specific number of high res pulses, but in earlier year manuals (1994 and 1995, for example) the number is 720 high res pulses (4 revs of crankshaft), with no high low pulse detected.

In OBD-2, this code should turn on the SES light. When the code sets, the PCM disables the fuel pump and injectors (94/95 specifically mentions pump and injectors, 96 manual only mentions "the injector will be disabled for the entire ignition cycle", but I think they mean "injectors"). If you have the code, and the engine is running, it is a stored code, and the problem is intermittent.

That explains why "the car cuts all engine power". This can be a problem with the optical module in the Opti (Gary had repaired poor solder joints in the cheap Chinese Optis), or a problem with the harness or harness connectors. Check for missing insulation - a short between the high and low res signals will set P1371. Check for corrosion or pin damage on the short Opti harness connectors, particularly the connector that inserts into the Opti. It isn't unusual to find some blue-green corrosion on that connector if the seal in the Opti isn't good. Even if the harness is new, I would still check the mating connectors in the main harness and Opti.

Going back to your first post, appears you measured fuel pressure when the pump primed and watched how fast the pressure dropped. Did you also measure the pressure with the engine idling, both with and without the vacuum compensation line attached to the fuel pressure regulator? Have you measured the pressure with the engine under heavy load/high RPM? How did you confirm that the Buick injectors have the same flow rating as the stock F-Body injectors? Were they from a Buick LT1? Which injectors were you running when you ran the HPTuners data log? Does it still smell rich when running the correct injectors?

 

I checked the connectors and harness for the opti they're all good. When I last took the opti off there were drops of oil, only a few around the opti spinning wheel that mounts to the cam dowel pin. Is this from the timing case cover gasket? I wonder why it doesn't consistently leak if oil got in there, because there's only a few drops after being on for months. I know oil in there can end up damaging the opti.

I didn't measure the fuel pressure while idling or running, I'll check that too to make sure I don't have any fuel issues for sure and rule that out. I put the injector stuff in a previous post, it turns out the injectors probably didn't have the same flow rating, and now that I have the proper ones in it it doesn't smell rich. In fact it's running like 7% lean fuel trims show at idle after relearning. Yes the old injectors were the ones installed when I recorded the HPTuners log. Next I need to catch up and check a lot of the stuff you guys recommended, especially the low resolution signal which is intermittent, so might be a little more annoying to catch. I'm an electronics engineer student and I'm pretty interested in how the low resolution signal looks when it's failing so intermittently so I want to see it on a scope. Thanks for all the help.

 

It's a simple 0-5V square wave. The problem is generally whether the pulse is there or not. not the precision of its shape.

And to be clear, the HPTuners log you posted, which shows the idle LTFT’s maxed out at +25% additional fuel, plus adding 6 to 9% extra fuel using the STFT's , is for the old, incorrectly sized injectors, not the injectors you are running now. Not sure what the purpose was of posting that log. It just added confusion.

 

Hey Gary the software connects now with the new adapter but the PID list doesn't appear when I click connect, and scan buttons stays grayed out. I'm clicking the connect button on the Live data screen. Here's the log: https://drive.google.com/open?id=1-T...V60J9Ykk1EF5O8

 

Have you tried clicking on Start Scan? Does the VIN appear?

 

I did try clicking scan and nothing happens. I don't think a vin is showing anywhere, where is it supposed to appear?

 

The VIN should show on the left side.
Check the settings to make sure the Get PID list at connect time is checked.

 

Run the program in administrator mode

 

Ok get PID at connect time was just disabled, now it works thanks but I have another question. How do I get the fuel trim cell beyond just the basic fuel trims data? I don't see it in any of the options I'm on the enhanced GM parameters version.

 

The items in the enhanced tab list are editable. It is mostly a DIY feature. You can add, delete or change any things there. Unfortunately you can only add items that will be displayed in raw form only, not scaled with any units. The Enhanced tab is separate from the main live data tab. It has it's own controls. While both can be run at the same time, it will not save both to the same file, so they will not be synchronized. Changes made to the enhanced tab table are NOT saved at exit.

The best information I have is an extract from a commercial program. It is in Excel spreadsheet format and shows the description, the four-number PID and the range of values.

Example: Fuel trim cell number uses PID 1190. It will theoretically return a raw number between 0 and 255. I assume it will be the actual trim cell number. There is no reason to expect otherwise. The fuel trim number is not a standard OBD2 required value so it will not appear with OBD2 data. It is purely GM. But you can add OBD2 PID's to the enhanced tab table also, by using two leading zeros added to the OBD2 PID in 2 digits. i.e. OBD2 PID 12 becomes 0012.

 

Text format list of the PID's for a 97 attached

 

Hmmm I see. What about the fuel trim cell PID? I should be able to add that PID myself right since it's not in there? If that's the case do you know it? I can't seem to find the PID number online for the fuel trim cell, or any of thePIDs for that matter.
Edit: Just saw the list you posted, thanks!

 

The GM PID list is proprietary information that is highly guarded by GM. They change $50k for the license to use it in a product. I "borrowed" these from a program that evidently paid for the license. They made it a bit too easy to extract the PIDs. I cannot guarantee that any of these are correct, but the ones I have tested do verify.

If you want to experiment to see what PID's are available on your pcm, you can run the Advanced utility on the lower left area of the Console tab. It will scan for any valid PID's and save the list to a file. Of course, the scan will tell you nothing about their function but at least you know which ones are available.

By the way, all PID numbers are shown in hexadecimal format but the returned values are shown in decimal format.