Pontiac Transport 1991 3.1 vin D NO check eng lite.

Sorry for the delay, I was away this weekend. The first path that has to be crossed is the communication with the ECM. A fuse is a likely starting point, has it been checked?

When you first turn the key on does light illuminate breifly?

You sound experienced more than most so I will assume you have.

Those older 3.1 motors were plagued with injector problems that if caught early enough were able to be cleaned. Still the would set a misfire code.

Have you checked the fuel pressure and volume?

Hi, Thanks for answering.Yes I checked for fuel pump pressure.No volt sence at fuel pump and
no pulse at injectors.I disconnected the complete alarm system and reconnected the fuel pump wiring like it was originally.There is continuity from ECM to
fuel modual.There is + and - going to the ECM.Like I said engine will run with carb spray. ECM is not puting out injector pulse or fuel pump sence.I was told on some GM modles that if the Crank sensor
is no good or shorting I will have no communication with ECM and check engine lite will not come on.
This is my problem NO COMMUNICATION WITH ECM.Therefore I cannot scan.Also I was told by the dealer that this model does not have a crank sensor.
But if you go to online parts it lists one??I have a picture but no location of sensor?? Your help is appriciated.
48chev

[quote:94b11e50f0="48chev"] I will have no communication with ECM and check engine lite will not come on.
48chev[/quote:94b11e50f0]

Does the CEL illuminate breifly when the key is turned to the on position for the bulb check?

DId you check the ecm/fuel pump power fuse?

There is no crank sensor on this one that I can find. PArts store sometimes list things that are nor accurate. Cabin air filters are one of the best examples :x :? . Also check this 10 amp fuse:

Hi, Thank you for all the input. I replied to your request.The diagrams you sent me are very helpfull, I am going to check all what you had listed including the bulbs in the dash for MIL iight. My problem is I need to tow the vehicle back home.It is stuck where it is very difficult to work on.This might take a couple of days.After I make all of the checks you had mentioned, I will post the results. Thanks Again 48chev

I just want to make sure the bulb does illuminate...probably does.

I'll catch up with you when your ready. Before you tow it, I would check the fuses I mentioned, it may be that simple.

[quote:25d573873d="Service Writer"]I just want to make sure the bulb does illuminate...probably does.

I'll catch up with you when your ready. Before you tow it, I would check the fuses I mentioned, it may be that simple.[/quote:25d573873d]

Thanks I will check the bulb/fuse Car was towed today,I will be in touch and keep up my obligation
to your wonderful forum.

Thanks
48 Chev

[quote:c08ec2b6ba="48chev"][quote:c08ec2b6ba="Service Writer"]I just want to make sure the bulb does illuminate...probably does.

I'll catch up with you when your ready. Before you tow it, I would check the fuses I mentioned, it may be that simple.[/quote:c08ec2b6ba]

Thanks I will check the bulb/fuse Car was towed today,I will be in touch and keep up my obligation
to your wonderful forum.

Thanks
48 Chev[/quote:c08ec2b6ba]

Hi ,
The fuse you sent me a diagram to check was the first fuse that I checked from the begining.I checked the
MIL bulb(check engine light) and it is OK
This is becoming a real Ordeal! What else can you think of that would cause No communication with
ECU and no Check engine light and no fuel pulse.
What about a fuel pump relay? where is it located?

Thanks 48 Chev.

Get an assistant to turn key On, At the fuel pump connector,do you have power at gray wire you gonna have this power just 2 secs. then its gone and should be there at all times while engine is being crank over. If power is at the gray wire you have a problem the F/Pump. Familiarize yourself with the circuit below its gonna come up

From 48 Chev Hi ,I will return to car on Sunday and will check power at fuel pump Again. That is also one of the first things I did.If the relay is under glove box which one is it. I need a diagram with pin # at ecm and exact location of fuel relay to check it properly.After I check I will answer . Thanks 48 Chev

F/P relay is in No.3 on the bottom left corner there's 3 square boxes the 1st one close to the fender

Fuel Pump Circuit

Hi, I checkedthe fuel pump circut.It is receiving 12V and relay will feed power to the fuel pump when manually activated .ECM is not putting out a signal to injectors or fuel pump.The Ecm is receiving + when key is turned on.The gray line from relay to fuel pump delivers 12V to pump when relay is manualll activated.I switched relays no help.ECM not responding.I checked Ignition The distributor was replaced with fuel pump at the very beggining. The oil sender seems to be OK.Is there a good way to check that?What else?Both fuseable links are giving 12V. Is there some type of Shut down switch/relay like chrysler has? It is too bad that the check engine lite does not come on ,If I can scan that would help! Thanks 48 Chev

The oil sending unit is like the Ford's inertia switch it kills the fuel pump when there's no oil pressure

The fuel pump relay energizes the fuel pump for 2secs then shuts off, when the van fires up the OSU takes over the power to the pump.

Double check all your power input to the PCM and its ground-If the computer cannot energize the fuel pump relay it gots an internal problem. Reflashing it will not work. Replacement might help.

[quote:34650092f6="rasmataz"]The oil sending unit is like the Ford's inertia switch it kills the fuel pump when there's no oil pressure

The fuel pump relay energizes the fuel pump for 2secs then shuts off, when the van fires up the OSU takes over the power to the pump.

Double check all your power input to the PCM and its ground-If the computer cannot energize the fuel pump relay it gots an internal problem. Reflashing it will not work. Replacement might help.[/quote:34650092f6]

From 48 chev
Hi,I will try to replace oil sending unit but I don't know why or what that has to do with no computer communication? What would help is a pin out # of
all of the ECM connector(s).so I could check. Like I
said in my previous listings.There is (+) and (+) after switch at ECM also( -).I ordered an ECM relay? If ECM is getting power I can't see how that would help.After I check ECM connector pin outs I will order a new ecm. Is there a listing (other than GM)that has pin # and location at ECM.

Thanks 48 chev

Hi, Thanks for the diagram for ECM !!!! With this I will check all the pins,sensors, conntinuity in wiring from ECM (with ECM disconnected)to DLC and hopefully get down to the question why is there no response from ECM? I had already checked the things above and feel this is my next step. Thank you so much for all the imput from you and members .I will post the results of my findings. 48 chev

Hi, Thanks for the diagram for ECM !!!! With this I will check all the pins,sensors, conntinuity in wiring from ECM (with ECM disconnected)to DLC and hopefully get down to the question why is there no response from ECM? I had already checked the things above and feel this is my next step. Thank you so much for all the imput from you and members .I will post the results of my findings. 48 chev[/quote:99c739c8e3] From 48 chev. Well some good news,with the help of you ECM diagram.I found another power supply at ECM that was not receiving the full 12V.It is receiving about 3 volt. It is Pin # C16 .It joins with B 1 also an orange wire at a fuse link I can't seem to find. I supplied an external 7.5 A fuse to power the ECM. and the check engine light came on and I was able to Scan the system for DTC'S. Being there were no DTC'S I then started the engine and checked all of the parimeters to find out that everything looks normal and all systems are working including cooling fan when reached operating Temp. My next step is to find that (rust fuse link C J/B) if you might have an idea where that might be that would be helpful. I want to thank everyone who has helped and a special big Thanks for that last wiring Diag. Thanks 48 chev

I'm pretty sure the J/B means Junction Block.
Glad to hear you are having success.

Hi I have the same symptoms with my 97 Trans sport. Does anyone have the wiring diagrams for my model? It is Pontiac Trans sport 97. 3.4 engine.
Thank you.

Hi,
Since that last problem with the Pontiac Trans Port I purchased OTC Autodata which has the wiring diagrams.You need to get the engine number or proper info for the correct diagram.Also you must know how to find out the pin numbers on your computer to be able to trace them down. May be your fuse is blown 7.5 amp ECM at fuse box?
see if check engine light is on and get a scanner to hook up to it.
because in 97 it is already OBD II they sell them cheap on Ebay.
I hope this helps
48 chev