1995 Dakota, V6, 2WD, automatic, fuel injected, 86,000 original miles, well maintained, 2nd owner:

Recently tuned up: new plugs, new wires, new cap, new rotor, new coil
Ran fine for months after those upgrades. No issues.

Just started acting up: stalling at idle unless I'm pressing on the gas, sounding rough, not going into 4th gear after warmed up on the highway, .....

So I checked the engine codes via the flash method and an Actron CP9190 - first time that was done in a couple years - check engine light never stayed on - here is what surfaced:

P0505 (or 2/5 flashes) = IAC motor circuits
P0600 SPI communications
P0403 (or 3/2 flashes) EGR solenoid
Speed Control (or 3/4 flashes)
--- ASD Relay circuit (4/2 flashes) anybody know what this is - auto shutdown???

So these items were then replaced with brand new ones:

IAC - done twice, thinking first one was defective
TPS
EGR and solenoid
Vehicle speed sensor
and for the hec of it, disconnect/reconnect the battery

Now when cold, it may start up and run OK for awhile but still then craps out when at operating temps. Sometimes when cold, it just craps out right away and won't hold an idle. Always starts easy enough. Very inconsistent and frustrating.

So when I check the codes again, after first clearing them, they ALL come back again and again

IAC, EGR, SPI, ASD????

After like ~ $500, I still don't really know what is going on???? All vacuum lines seem fine.

Could it be:

That ASD thing I have no clue about
2 wire coolant temperature sensor that feeds the PCM (where is this thing - hard to find - underneath the AC compressor?)
air temperature sensor
crankcase/camshaft position sensor
fuel filter, fuel pump

Guessing something else is tripping all those codes again and again. But what do you think that is???

THANKS VERY MUCH IN ADVANCE FOR ANY IDEAS!!!!!

Dave H. Appleton, WI 8/3 9:30pm

 

what is SPI? and a 95 wont yet have P-codes.... that was still a year off.
Id say it aint the ASD or it wouldnt run at all.
the 2 wire switch whaddya mean "bitch to find"? I dont seem to have a problem finding in the parts stores but I doubt your issues are there either

clean the ISC passages in the throttle body and checek fuel pressure next

 

UPDATE:

This forum is so amazingly useful!!!! Kudos to the owners/operators.

I found the specific FSM (factory service manual) for a 95 Dakota and did some reading - see quotes below.

Thinking this COOLANT TEMPERATURE SENSOR might be my next item to try since I already replaced the VSS.

This MAY explain why I have idle problems AND a weird tranny issue when warm and at speed. Kinda connects the two maybe???

 

That is what I would suggest for the OD. But since you keep getting the speed sensor code it might be that is failing again or bad wiring.

The IAC may be bad even though it is new. Tons of new out of the box ones are bad. If you got your receipt try replacing it again, and maybe again. Trust me lots of us have to return them several times.

The EGR problem may be a clogged intake or bad wiring or bad vacuum lines since you replaced it.

The ASD is what give the power to the coil and injectors, while the PCM controls the negative to those circuits. The ASD relay is activated by the PCM every time the engine is running ect. The name kinda those people off, it is called ASD since once the key is off the power to those circuits gets turned off.

 

With my Actron, for 90 minutes i watched the datastream. Nothin seemed weird except:

Trans sensor voltage was 5.00 and minus 127 F.

That seems bizarre.

Next to check.

 

what "trans sensor"?

 

i think there is a transmision temperature sensor. anyone know if it has one and where it may be??? thx (i'm on the road otherwise i'd check the FSM.)

 

IAC may be bad even though it is new. Tons of new out of the box ones are bad. If you got your receipt try replacing it again, and maybe again.

NO KIDDING 4x4, i am on the 4th one!!!!! maybe i'll head for a salvage yard

 

no, sorry no trans temp sensor yet on 95s, when they went to OBD 11 and RE vs RH series trannys in 96 models and newer the only trans temp reference is one of the 2 coolant temp sensors in the coolant passage at front of intake manifold.your truck will have both. One has a single wire the other has 2 wires; IIRC the 2 wire one is the one that gives computer related temp inputs, the single wire one controls the gauge on the dash.

 

UPDATE 8/6/2012:

Here is what we did today/tonight:

#1) added about 6 ounces of tranny fluid - looked just a tad low.

#2) pulled the PCM connector - lot of dust and spider webs - looks like it was replaced in 2003. Blew out the crap. Deox'd all connectors (Caig R5). Some white oxidation present. No rust or signs of water.

#3) cleaned and deox'd battery ground and any other grounds I could find under the hood.

#4) removed battery negative cable for an hour.

#5) my Actron showed the PCM was getting proper engine and air temperatures. So I didn't touch the incoming air or engine coolant sensors.

BEFORE all this, I had these FIVE codes come up repeatedly even after clearing over and over:

* P0600 / SPI communications MIL 053 (internal PCM failure)
* - - - - ASD Relay circuit MIL 042 (fuel/ASD output)
* P0443 EVAP MIL 031 (EVAP circuit open or short)
* P0403 EGR solenoid MIL 032 (EGR circuit open or short)
*P0505 IAC motor circuit MIL 025 (IAC circuit open or short)


GOOD NEWS: No codes at start of test drive. Drove at highway speeds for an hour and a half. STAYED IN FOURTH GEAR!!!! Got home and only ONE code:

*P0505 IAC motor circuit MIL 025 (IAC circuit open or short)

This code comes back instantly after being cleared. AND I AM ON MY FOURTH IAC - #1 and #2 Autozone, #3 Advance Auto, #4 NAPA. I am going to the dealer tomorrow to get an expensive OEM one to see if that does the trick. Cheap *** parts huh??? Dang it.

Now the only thing strange is the idle when hot constantly fluctuates from 800 to 950 rpm - IAC stays at "0". But the O2 sensor goes in sync with the idle from 0.05 to 0.95 volts. Is that normal???

That is the only datastream I see fluctuating with the idle speed. Think there is a correlation there????

What do you make of the above results???

Thanks everybody.

Dave H. Appleton