Hi, I've noticed on several threads/topics it is mentioned that once you have corrected a OBD fault code, it is (or may be) necessary to "reset" the VCM. I found the info on EGR testing/cleaning but the code p1404 still comes up after the usual 2 start up time period.

Is that something I can do? I have a code scanner and can/have erased the code but the admin. here mentioned that the vcm needs to be reset or it will remember the last code, specifically for me the "closed" EGR system.....

 

If you have cleared the code and it came back, you have not corrected the problem. Resetting the PCM will not change this. If you want to give it a whirl, you just disconnect the battery for 10-15 minutes.

 

If you "clear" the code you are erasing it from the memory, but not remedying the problem. If you have removed the EGR you may need to correct for the pintle position.

Useful thread: P1404 Explained

 

Well twice now I've checked all 5 wires, 12v power source on the red wire; the 5 v Reference wire next to it; the Pintle Position Signal, the ground wire back to the PCM and checked the voltage as I pushed the pintle itself back up into the orifice.

I've taken the EGR valve off twice also and cleaned the pintle itself with a small wire brush and cleaner, and checked to make sure that I don't see any crud/carbon near the seat or on the base it sits.

After doing this, I've even bought a new EGR valve, installed it but the CEL came on after a two trip cycle. The code keeps coming up p1404.

Should I now suspect the PCM?

 

Well.....decided to re-do everything for a third time, EXCEPT when it came to testing the v supplied to the pintle circuit I checked with the harness attached and the EGR installed. Before I had taken the EGR off and was testing the voltage as I pushed in the pintle into the EGR cavity. On that method I got .79, .75 on several times up to 4.5v., which is what is supposed to read. BUT, when I checked with EGR installed, the pintle circuit was barely getting .1 v; which leads to blockage of some kind. Knowing that I've cleaned the dumb thing and the pintle seat, and the base it sits on, lead me to believe that the new gasket with the screen somehow was impeding the full extension of the pintle.
Took off the gasket, re-installed the pintle and now I get .79 v to the pintle...

Can I apply a thin gasket maker around the two cavities and get by with that, or should I find a different gasket??

 

I finally put $18 up at "Just Answer" and got to a 18yr Cadillac GM a.s.e. certified mechanic who told me there is a GM bulletin concerning the need to "reflash vcm" for 1998-1999 Chev. and Isuzu hombre with the 4.3l engines.

Electronic noise in the Vehicle may create momentary false "low" exhaust gas Recirculation pintle position feedback signal values. Severe occurrences may cause the vehicle control module to set a p1404 because it senses a stuck open condition..

REVISION: 09/03/98 DIVS INVL 1 3 5 7

Hopes this works out, as I'm riding exp. tags now and need to pass local DEQ.

 

Where is the VCM located in a 1998 Blazer? Judging by the wiring diagram it looks like it is under the hood, but can anyone give me a more specific location?

Also, does the VCM go by any other names on auto parts sites? I can't find it listed on Rockauto whilst trying to get a quick price figure in my mind.

Thanks in advance!

 

It sits on top of the coolant reservoir on the passenger inner fender. The most common name for it is PCM (powertrain control module).

 

Thanks, I know what you're talking about and PCM definitely brings to mind a lot of material that I've seen on here and in my manual.

If a short circuit is happening in the PCM is there hope that I can open the PCM and fix it or are they just replaced and thrown away? Is this plug-and-play or does it need to be programmed before working in the vehicle?

I am experiencing the 'Gauges' circuit shorting into the '4wd" circuit and shorting the latter. I've eliminated most other potential locations for the short and am left with the PCM.

 

It is very doubtful that you will be able to open the PCM and fix an internal fault. Just trying to open it can be 'fun'. You could give it a try though. If it isn't working now, breaking it more probably won't matter.

As far as another PCM is concerned, it will need to be programmed to your VIN and you will also need to have a CASE Relearn performed to calibrate the PCM to your engine & sensor variances.

Do both of those circuits run through the PCM??