Hi all, new to 3rd Gen and don't know if I should be here but anyway I have 3 TBI vehicles and after reviewing a number of other forums for GM vehicles, this forum appears to match the direction I may go with at least one of my vehicles.

I presently run a 93 Caprice Classic Estate Wagon, 350 TBI & 4L60. I also run a 95 Chev Suburban K1500, 350 TBI & 4L60-E. I also have a parked 87 GMC Rally STX, 3/4 ton, 350 TBI & 3 speed trans.

I keep the large vehicles to carry the wife, the groceries and 300+ lbs of dogs.

I am looking to get better performance out of my Suburban, mostly for fuel economy. My van gets 15.6 USmpg, my Caprice gets 20.2USmpg and the Suburban gets 13.0gpm. To me this doesn't compute. The van gets 2.5mpg better mileage and its 8 yrs older, wider, taller, 1600 lbs heavier, same size wheels and only a 3 speed trans. I realize there is a penalty for the 4WD but that much?

In the interest of not being held to ransom at the dealerships for repairs and good jobbers are hard to come by, I'm trying to get to know more about ECM & PCM controlled vehicles. Cost me $800 for the dealership to find a faulty fuel pump relay.

So having been screwed due to lack of knowledge I bought a code reader only to find later a $1.00 jumper would have done the same. It wasn't a total waste of money because it showed me how to read the flashes on the SES. Then next I thought I would be better of with a scan tool and that's another can of worms. $200 units do just that while a usefull scan tool will cost thousands. Then I read about free software on the Internet which can monitor and even make changes if you get the right set-up. And thats why I'm here. I have TBI's, looking to do my own diagnostics and may eventually get into the chip thing, but at this time and reading Traxion's stuff, that's a little daunting and overwhelming.

Sorry for the essay,
Bram

 

Okay, to get you started in the correct direction, you will need a laptop, an ALDL cable, and software. The software is a free download from tunerpro.net. The cable is available from aldlcable.com or moates.net or search for a schematic to build your own. I think the 95 suburban is still a OBD1 vehicle, so that setup will work with all your vehicles. Read the stickies, and data log your suburban and then you can start asking questions.

 

If the engine is running smooth, the 1st thing I'd check is the engine coolant temp sensor on the scanner. Should be 190-200* going down the road, a cold or defective t-stat is a mpg killer.

 

The 1995 Suburban is running a 4L60E tranny, so no it's not OBD1, it's OBD2 - have to have the OBD2 setup in order to work with the electronics of the 4L60E tranny.

 

Isn't the 16197427 a OBD1? Pretty sure it does the 4l60e...

 

I suppose it could, I just always assumed that the 4L60E tranny by default meant an OBD2 system, since the 4L60E tranny was completely controlled by it's own PCM that needed input from the ECM. But if I learn nothing else in this world, I've learned that even if it's writen in stone it's not always true

 

Thank you all; I have been doing lots of reading, this site and others. The more I read the more confused I get. 8^) My 95 Suburban is definitely OBD1, I have the 12 pin ALDL connector and my shop service manual states to use Tech 1 which is OBDL1. I definitely have the 4L60-E (case stamp is M30) and from DIY-Prom, GM-ECM site and Moates I am pretty sure my memcal will be 16197427, not looked yet. The EPROM type should be 27C512 and the baud rate should be 8192. Some of these things come from very old info and could be in gray areas.

For my truck the "PCM" runs the whole show and that's what it is called in the shop manual. The shop manual also includes the standard transmission details and in that section, the computer is called the "ECM".

Functionally the vehicle runs fine, it is supposed to have a brand new (8K miles) factory crate engine. The idle is a little higher than spec maybe 50 to 100 rpm.

 

yeah it gets confusing especally 94-95 years. Earlier is OBD1, later is OBD2 and the change over years 94-95 are like OBD?

But what you are saying is correct, the 16197427 is called a ECM but in reality it is a PCM. It's a way better ECM for TBI trucks then the earlier 1227747 but the real purpose was the tranny controls! Stranger than that is I have seen one used in a manual transmission as well...