1994 K1500 ECU Pinout (or any GM TBI)
 

Anyone have any idea of the pinout on the ECU? Specifically I'm trying to figure out which one is the O2 sensor because I really don't want to cut into the line under the truck. Any idea Jay? I can't find any info online. Do you have the shop manuals?

I've tested a few pins but none are even close. When in doubt I'll just cut in I guess.

I have no idea. I have all the shop manuals for Rusty and the Big White Hooptie (I even have the factory parts manuals for the BWH), but none of that for The Beast - it hasn't been needed. Even if I did I imagine it still wouldn't do any good as my truck is OBDII, and yours isn't. Try to see what color the wires are in the harness coming from the O2, and see if you can find them going into the computer.

-Jay

Tried that, guess I'll go play again.

I must have just seen the wrong color last night, I had no trouble locating it today. Not sure if my DMM is picking up every change or dropping a few but it spends a lot of time in 600-800mv territory with a flash to 45mv now and then. I guess that's 'good'.

There was another purple wire near by that is at 1300mv when idling and seems to increase with throttle/load of the engine, it doesn't appear to be RPM or throttle (engine off, power on, throttle does nothing), but it varies between 1400-1900 for quick (50% throttle) accel. Maybe I can do something cool with that.

on the red 32pin connector
a10 - o2 sensor signal - purple
a12 - o2 sensor ground (engine ground) - tan

for reference finding the correct wire
a9 dark green
a11 not used
a13 not used
a14 white/black
b10 white
b12 gray

....hopefully the info is correct/ same as yours

I'm glad you found it. The best way to double check that you got the right one is to force your truck into DFCO. Its best to do this when there is no traffic. Go to the top of a large hill. After you pick up some speed, downshift to engine brake. You want your RPM's to stay over 1500 without any help from pushing the throttle. If you have the O2 sensor output anywhere between 3 seconds and 10 seconds you should see the output fall signifigantly and stay there until you tap the accelerator pedal.

-Jay

That sounds about right, where'd you find that info I couldn't find anything online.

Also do you think that ground is just the 2 wire sensor ground or used for the heat element? My O2 has 3 wires coming off it. If it's the ground I'm thinking about a resistor inline or something but don't want to affect the heat element.

I missed this thread, but FYI: If the local library doesn't have/can't get you (through inter-library loan) a Chilton's/Haynes, they may have free online access to the EBSCOHost Auto Repair Resource Center.

GM calls it PCM (Powertrain Control Module), not ECU, so that might help with googling for it. Additionally, check sites such as fullsizechevy.com, gmfullsize.com, gm-trucks.com, etc.

the pcms sensor ground doesn't go to the sensor, it just goes to the engine block

the 3 wires on your sensor, 2 white are power and gnd for the heater, blk is the signal

btw congrats on 18mpg, beats out my single best tank in my 91k1500 of 17mpg that was nearly one continuous burn down the interstate at 60mph or less haulin a motorcycle. normally mine lives around 13mpg, but when it gets to come out its almost always werkin.

itjstagame,

Check your PM's

;)

moorecomp

https://www.gassavers.org/gaslog/sig.php?id=1983