99 Blazer 4dr 4wd Electronic Transfer case Almost always in 2wd.

True story: So, the wife says the check engine light came on. I jumped in the rig and went for a drive – had no check engine light on.

Scanned with Innova 5610 P0171 shows up in Global OBD2.

OEM Enhanced had this mess:

OEM Enhanced codes: P0;101, 106,121, 125, 131, 132, 133, 134, 135, 143,144, 146, 147, 151, 152, 153, 154, 155, 171, 172,,174, 175, 300, 325, 327, 401, 404, 420, 440, 442, 446, 461, 500, 502, 503, 506, 507, 601, 603, 604, 605, 713, 742, 751, 756, 1133, 1134, 1153, 1154, 1345, 1351, 1361, 1380, 1381, 1441, 1810, 1870, 1875; U: 1042, 1192, 1193

Scanned about 1/2 hour later. Here’s what stays:

OEM Enhanced codes: P0 - 125, 133, 134, 135, 143, 146, 147, 153, 154, 155, 171, 420, 440, 442, 446, 605, 742, 751, 1133, 1134, 1153, 1154, 1441, 1810, 1870, 1875; U: 1042, 1192, 1193



I’m thinking discount battery negative and allow modules to go to sleep for an hour. Remove PCM and “Corrosion X” everything.

Any help is Greatly appreciated.

Tom

 

Todays' scans include Innova 5610 and Tech2. Prior to doing anything repair-ish:
Codes are P: 0171 (Tech2 says passed). This is the only thing I found on Tech2.
Innova 5610 - P: 0171, 420, 605, 751 U: 1042, 1192,
Any thoghts, experience or help ? this would be Greatly appreciated.
Tom

 

Have you used your scsnner to clear the codes to see which onrsme reset?

Are you needing help with decoding the codes?

 

Some scan tools are very peculiar as to what they display as codes. They can often display codes that are what I'll call 'phantom' but what really is a precursor fault as in they wouldn't even make it to the true pending codes list on a factory scan tool or pro-level scan tool, but they technically have hit the precursor level in the ECM to be stored into memory for further markup if the same issue reoccurs. The Tech2 will only read pending & hard codes which have passed through the validation process GM set in the logics of the ECM code set criteria. The Innova isn't limited by that logic and can access everything in the ECM and list anything it damn well pleases much to the confusion of everyone watching as it doesn't differentiate what it finds from "hard fault", "pending fault", or "precursor fault" (what I am calling a phantom fault).

I would concentrate on the P0171 code and ignore the rest or you'll prematurely go bald and broke in the process. This specific code has been discussed quite a bit on the forum. You can run some searches, but I would start by checking for vacuum leaks. Maybe see if the MAF is dirty, but that would sooner affect both banks equally as would low fuel pressure.

 

That's good info to know, Swartlkk. I didn't realize that some tools did this. Definitely something to keep in mind when shopping for a new diagnostic tool. Thanks!

 

would this be the one?

Tech2 Scanner for GM Diagnostic Tool Tech 2 ​with CANdi & TIS2000 For GM

 

Thank you, guys, for the input and steerage. What I found was the line to the fender mount vac reservoir had died of old age. Also, the vent tube from RH valve cover at the air inlet was wobbly. Replaced the reservoir vac line and added a constant tension clamp to the 90 at the air inlet to throttle body housing. So far, everything looks good. Truly doesn't begin to explain the OBD code extravaganza.

 

So I guess I should have elaborated more as I tried to explained that your scan tool may be showing information that should be taken with a grain of salt as the source of that information might not have passed through the full OBD2 logic fault test criteria to actually set the code. It could have set one single detection in what could be a very lengthy list of criteria to set the code. Without context into why the scan tool is showing that code, you could be chasing blindly down a rabbit hole that does not need to be chased down at that point in time.

For an under the hood description of what is happening inside the ECM... Fault detections occur all the time that may or may not actually be a problem. These detections get recorded into the ECMs memory for comparison against the rules set by GM in the code set criteria logic tree. They may reset after so many successful test cycles or they may just sit there and wait depending on the test/variable type. Once the criteria for code set is met for PENDING status, the code is elevated to that status level and displayed as such on a scanner that obeys these rule sets. The next level up is HARD status. In later models, there are PERMANENT codes that persist past code wipes and will not reset until the condition is found to pass the logic tests again at the next test cycle.

Could it be these detections stored in memory that your Innova scan tool is listing off as codes even though they are have not made it to the pending status level? You would have to determine whether the tool shows the status level of the code and is programmed correctly to know whether it is PENDING, or HARD; maybe it has it's own descriptor for PRECURSOR codes? If the scan tool is actually classifying the codes properly then great, it should list their status in each individual code if you can open them separately, but I am unfamiliar with the Innova tool line. I'm just trying to explain what could be happening here as I have seen it on other consumer scan tools that are out there. I would not get too invested in PENDING codes until they become HARD codes.

I would definitely go with Christine's advice on wiping the codes. I would make a report to save the codes you have listed, then clear the codes and drive it for a while to see what codes come back up again as many times there can be some pending codes stored that are from old events such as low voltage from a battery disconnect, maintenance, or other such events. It is always best to save a report with everything you have listed to start, then wipe, drive it to get whatever faults to repopulate, and see what comes back. It could take awhile for a drive cycle to complete though so be aware of that.

Good luck!

 

Well said and described. I thank you for your time and help.