I re-read your post as apparently I had skimmed over it the first time... I thought "that is not correct"... re read MY post and realize that I was definately not clear and my rush to get you data caused conusion. I will edit my original post to more clearly define the data.

The output signal from the ECM is to the sensor circuit 5v and once passed through a warmed Titanium Oxide (narrow-band) Oxygen Sensor that supply voltage will drop if the circuit in the sensor is functioning properly. What that exact "return" voltage will be depends entirely on the gasses detected (specifically O2 based on how it reacts with the Titanium Oxide causing the increased resistance) as the engine runs lean and rich in its constantly varrying state.
The Bosch (Motronic) systems converted to 4 wire Zirconia sensors later in '99.

 

Thanks, that clears the interrogation my brother and I were having. I'll take a look at the truck tomorrow and hopefully have a definitive answer to this problem.

 

Hooked the truck to a Snap-On testbook this morning. I got 4 codes showing up. And the truck has run rough for 10 seconds on start up and ran fine during the whole drive. And fired right up all the times I restarted it.

P1317 - Rough road line
P1193 - B2 S2 Open heater circuit
P015? - B2 S2 High voltage output
P1508 - IACV open circuit (allright something linked to my problem!)

Obviously there is one O2 that has completely crapped out. And I got a faulty IAC, which didn't show up when I tested resistance. And I know that the harness is fine because I tested continuity to the ECM. I erased the codes, I'll see if they come back. And I'll try to test the IAC again, and check if the plunger is stuck.

 

UPDATE - When I started the truck for my ride home tonight, hocus pocus the CEL disappeared on its own!

I ordered a new IACV that I will put in this weekend. I'll let you know guys how it turns out.

 

If the seal was gone before the Maf it is probably dirty now. Try cleaning it with a little electrical contact cleaner.

Jull my disco is a decepticon. When i put the decals on my wife said "Really".I'll have pics soon.

 

MAF is clean. I cleaned it a month ago after putting the new o-ring in.

 

Hey Jull,

Did you ever resolve your issue? I'm trying to root cause a warm start issue on my D1 and some of your info has been quite useful.

Thanks for any update.

Bob

 

I pinpointed the IACV as being the cause of my issue but I haven't changed it yet, my brother first forgot to order it, then kept forgetting it at work. I just got hold of it this week.

The problem I have is intermittent. The truck has been running extremely well since temp got warmer. I went wheeling twice and had no problems whatsoever with frequent restarts. It seems my old IACV is sensible to cold and humidity, causing an open circuit.

 

Finally got hold of a new IACV, so I'm resurrecting my old thread. I put it in the truck started and idled great... only the first time I started it.

I noticed the plunger was fully opened on my old when I took it off. Usually when I was cleaning it it was only half-way opened. Which leads me to believe that whether circuit of the wire loom used to retract the plunger is bad or the ECM itself is bad.

The main interrogation I have is that I checked the loom for continuity this spring and it checked out OK. Would a parasite resistance be enough to keep the IACV from opening? I think I can rule out any ground issue, this is the only thing not working properly on the truck..... I'm also having trouble with the headlights but they don't share the same ground.

I'm probably looking at a bad ECM.

 

After a month of sitting in the driveway because I was waiting for parts, I restarted my truck. The fuel sending line was leaking.

Symptoms are the same, won't idle but runs good when I hold the throttle, it doesnt hesitate on acceleration or going uphill. Which leads me to believe it's flooding on startup.

This is my last resort theory; one (or several) injectors are sticking open and leaking into the cylinder causing the ECM to restrict the fuel injection and the airflow (therefore closing the IACV) because the O2 sensors tell it it's running rich.
The problem started very randomly, only every now and then but as time went by it happened more and more often right up to the point where I'm now.

One of the only other thing going bad would be the ECM, but money is kind of tight right now and I can't afford to spend 100$ on an ECM only as a wild guess.