I have a 2001 Chevy blazer LT 4wd and it’s currently having issues but I’m not sure where to start.

Inital problem: when moving from a complete stop I would get some shaking/vibrations and when pulling into parking spaces or backing out of parking spaces some intense shaking. Only happens intermittently and usually at low speeds. At higher speeds I get some small vibrations but that is it. Acting almost like a manual when releasing the clutch too early and the engine stalls. Engine does not actually stall and I don’t see a fluctuation in RPMs when it shakes but it has a similar feel. Does not drive smooth and it feels like something is not working properly. Seems to shift alright but RPMs are low at idle (about 500 but doesn’t go lower)

Check engine light popped up for TCC stuck off (replaced solenoid)
Check engine light also popped up for a knock sensor (replaced knock sensor) and for EVAP Vent Valve solenoid (Also replaced)

Problems still occurring but the codes are not being thrown anymore under normal scans. Ran enhanced OEM and around 40 codes are showing up almost every time. Engine misfire to electrical codes etc. If I erase them they immediately come back. Thought it was the ECM so I got a replacement flashed to my VIN. Followed security relearn procedures but have not done crankshaft position relearn yet (it’s a weekend and I don’t have the tools).

Wondering why my ECM is throwing so many codes still? It’s the same thing my last ECM was doing.(I have reset both the new and old ECM modules).Wiring seems fine (a little dirty on the outside but the connectors are spotless). I also have no clue why my truck is acting up? It will drive but I can tell it’s not working properly or like it used to.

Does have new CV axles so that should not be a problem. Any suggestions for next steps? I’m thinking I may have to bring it to Chevy for diagnostics but I was wondering if anyone has had similar problems? Seems like possibly a wiring issue to the ECM ? I’m thinking it’s getting incorrect data causing it to adjust improperly and go into a safe mode. Any suggestions would be appreciated.

 

I have done some further assessing and I actually think it’s a drivetrain issue. I went into a parking lot and did tight circles then lifted the front end. CV axles or the diff.is my guess because it’s making some klunking noises when rotating the wheels at full extension. Which is causing the shuttering. I’ll update if it’s the CV axles because they are brand new so they should not already be failing (they are Cardone CV axles with 6 months of use). The ECM is a separate issue which is unrelated but still odd. I did also find a vacuum leak which could have also been causing problems.

 

Just a quick thought. What sort of transfer case do you have? If a 4-button, then there will be a clutch pack in it. Reading your symptoms I wondered if the transfer case was partially or intermittently engaging and disengaging. More broadly, I too wondered if it was a power train issue.

I can't see how replacing the front drive axles could be the cause unless the cj joints had gone bad.

Good luck and keep us posted .

 

It is in-fact stuck in 4wd and yes I do have a 4 button. I was wondering if anyone has the FSM ? Seems like the front driveshaft is engaged even when in 2hi. Took off the motor on the transfer case it works perfectly. So it seems like the issue is within the transfer case itself.

 

The 4-button transfer case has a viscous coupling on the front output shaft that has a certain amount of preload on the shaft. It will rotate the shaft even in 2wd. This is normal and nothing to worry about. On the other hand, operating the motor for the transfer case while it is off the transfer case is not a good idea... Hopefully it did not cause any issues.

As to your problem, have you checked to see that your front axle is actually disengaging when in 2wd? If you lift one front wheel off the ground with the vehicle in park and in 2wd, the wheel should spin freely. If not, you have an issue with the front axle engagement/disengagement mechanism located off the passenger side of the differential assembly.

When was the last time your transfer case was serviced and was it serviced using GM Autotrac 2 fluid as that is what is required for the NV236 transfer case due to the viscous coupling I mentioned above. Using typical automatic transmission fluid will cause issues with the viscous coupling. If you choose to service the transfer case yourself, pull the fill plug (upper plug) on the back of the transfer case first. This accomplishes two things; #1 it lets you know you can fill it back up & #2 it shows you that the fluid level is not abnormally high. If fluid comes out of the fill hole, you will need to remove the transfer case and replace the input seal on the front of the case as it has failed and is allowing transmission fluid into the transfer case, overfilling it as well as degrading it affecting viscous clutch operation.

It is very likely that you could have a number of these issues all at once as they are all very common occurrences on these trucks. Let us know how we can help.

As far as FSMs go, be careful what you buy into for the cheap PDFs out there. Many are garbage generic messes. There is a reason a used FSM set is still fetching close to $300. You could always go with a subscription to Alldata or Mitchell1 and get the TSBs along with it which is what I do for my vehicles.