Needing help with PCM connectivity 01 ST

[SKW1020]

Nice!! So the communication wires are connected from port to pcm

The issue is no start and Your scanner will not talk to pcm
So the thought process here is your pcm may not be getting powered up. Now that we know the can bus wires are connected from obd2 port to pcm, we can shift our focus to the pcm not getting powered/ working

So you are going to check pcm power feeds

When you turn the key the ignition switch powers/triggers the pcm/eec relay. It does this through an interior fuse (19) then through the power diode in the pjb (power junction box = fuse box under the hood) and then finally to the relay
The relay then sends battery power to the pcm and several engine sensors (injectors, coil packs, etc) via the red wire. This is vpwr circuit

So you want to check the grounds, which you did. The ground wires at the pcm should have continuity to ground

Now you are going to check the power side of the pcm
So to do a power check, basically test for battery voltage. Put your multimeter ground lead on the - at the battery terminal and the + red wire probe is your tester

First test pin 55
This should be power all the time. Keep alive power, battery voltage constant to pcm

Next test for power at the other power feeds, this time with the key turned to run
You should have battery + voltage at pins
71 and 97

Thank you so much for the laymens terms! I needed it that way. I'll get better, Hey, off subject, for the last 12 hours or so I have replacing my 83yo dads steering gear box in his 88 B2. tHis is his baby, and he keeps it like a pin! Anyway, I read about yours, and Im going to print it so he can see what all youve done, he will be amazed! His has a jasper v6 no mods really, but it really is clean. Here a few pics of it.

 

[410Fortune]

Oh man I would love to have that bronco! She’s a gem!
My little b2 started all of this many many years ago when the internet was new

 

[SKW1020]

Oh man I would love to have that bronco! She’s a gem!
My little b2 started all of this many many years ago when the internet was new

My dad works at Bass Pro Shops, and everybody always wants to talk about his B2... the other day someone offered him 20k, I was like and you didn't sell it? lol..

Anyway, I have 12.5v at pin 55

12v @ pin 71 & 97 with the key in run position....

 

[410Fortune]

You just don’t see them like that anymore she’s so clean would fetch big money these days

I’m going back to page one going to re read this thread now that we are making some real progress

 

[410Fortune]

Okay so here we are

The key still does not operate the starter.
Have you tried with the truck in neutral?
(Thinking the natural safety switch in the trans maybe off or your column shifter is loose)

When you jumper the starter relay and manually crank the starter
Have you tried a little starting fluid in the intake? Must put start
Fluid past the throttle body

Also you need to confirm if the fuel pump is priming running when you turn the key to run

Probably been over this, but we got stuck on the communication issue and pcm power
Now you have confirmed the scp wires are connected and the pcm is getting powered from fuses ignition switch relay

 

[SKW1020]

You just don’t see them like that anymore she’s so clean would fetch big money these days

I’m going back to page one going to re read this thread now that we are making some real progress

Man, I appreciate you! I'll recap as well.

I have continuity on pin 15 and 16 between scp bus wires + and -.
12.5v on pin 55
12v on pin 71 and 97 (key in run position)

 

[SKW1020]

Okay so here we are

The key still does not operate the starter.
Have you tried with the truck in neutral?
(Thinking the natural safety switch in the trans maybe off or your column shifter is loose)

When you jumper the starter relay and manually crank the starter
Have you tried a little starting fluid in the intake? Must put start
Fluid past the throttle body

Also you need to confirm if the fuel pump is priming running when you turn the key to run

Probably been over this, but we got stuck on the communication issue and pcm power
Now you have confirmed the scp wires are connected and the pcm is getting powered from fuses ignition switch relay

Ive tried cranking it while in neutral and jiggling the shifter, I have tried starting fluid, I can't hear the fuel pump oddly enough, so I'm not sure it is. I can make it crank with a jumper but no start. Is the radio supposed to turn off when I turn to start position? For some reason, the aftermarket radio comes on when the key is turned on to run position.

 

[410Fortune]

The radio should stay on
Something fishy there as you know… is the aftermarket radio wired to the factory radio wiring harness or did they run their own power wires? Many times they tap into the ignition switch with vampire clips and can cause some serious issues

If you unscrew the fuel fill cap and put your ear to it, have a helper turn the key, you should be able to hear the pump run

 

[SKW1020]

The radio should stay on
Something fishy there as you know… is the aftermarket radio wired to the factory radio wiring harness or did they run their own power wires? Many times they tap into the ignition switch with vampire clips and can cause some serious issues

If you unscrew the fuel fill cap and put your ear to it, have a helper turn the key, you should be able to hear the pump run

This is good advice, and I pulled the radio, and it has a factory adapter kit installed. I'll check the pump shortly

 

[SKW1020]

This is good advice, and I pulled the radio, and it has a factory adapter kit installed. I'll check the pump shortly

Well, oddly enough I dont have any help with this thing, so I put a piece of tubing into the gas tank so that I could hear the pump when I turn the key, and all I hear is the sound a conch makes, like the ocean, I dont think I'm hearing the pump at all.

 

[410Fortune]

Must get the fuel pump to run /
Confirm fuel Pressure

 

[SKW1020]

Must get the fuel pump to run /
Confirm fuel Pressure

Fuel pump relay has correct voltage I believe and is working correctly, have to drop tank to check pump?

 

[410Fortune]

No you can check fuel pressure at the fuel rail

You can jumper the fuel pump rely and force the pump to run, this way you can hear it and confirm fuel pressure

With pump running will truck start?

Also does a scanner now able to talk to the pcm?

The 99-05 sohc engine has a schrader valve on the backside of the passenger side of the fuel rail, fuel pressure test port

This is a picture of a 06 sohc engine
You can see the fuel pressure test port is located on the front of the drivers fuel rail
In a 01-02 the test port is usually on the backside of the passenger side fuel rail
I drew an arrow to it where it should be

Fuel pressure is 64 psi +/-

 

[SKW1020]

Must get the fuel pump to run /
Confirm fuel Pres

No you can check fuel pressure at the fuel rail

You can jumper the fuel pump rely and force the pump to run, this way you can hear it and confirm fuel pressure

With pump running will truck start?

Also does a scanner now able to talk to the pcm?

The 99-05 sohc engine has a schrader valve on the backside of the passenger side of the fuel rail, fuel pressure test port

View attachment 463715


This is a picture of a 06 sohc engine
You can see the fuel pressure test port is located on the front of the drivers fuel rail
In a 01-02 the test port is usually on the backside of the passenger side fuel rail
I drew an arrow to it where it should be

Fuel pressure is 64 psi +/-

View attachment 463716

I dont have a fuel pressure guage, however with the key on, I depressed the valve and fuel sprayed everywhere.... so my guess is that its working and still no crank. And my cheap code reader will not connect to it.

 

[SKW1020]

I dont have a fuel pressure guage, however with the key on, I depressed the valve and fuel sprayed everywhere.... so my guess is that its working and still no crank. And my cheap code reader will not connect to it.

Since I cant connect to the pcm, and everything else seems to be working like it should..... at what point would I look at replacing the pcm?

 

[410Fortune]

First check spark plugs
How do they look?
You can do a simple test and test for spark

If you have a check engine light and it goes off when cranking
And you have a theft light that flashes and then goes out while cranking it is not likely a pcm

Check those two lights
So the basic tests are check for spark
Check for fuel pressure
Check battery voltage
Then a visual inspection of the engine and fluids, filters.. no mouse house in the airbox, no large leaks, nothing disconnected
All fuses must be checked all of them
A fuse can be good and not be seated fully or not seated in the correct spot
The blades can have corrosion on them

After this it’s a compression test
The radio power situation is odd

There is no reason a scanner should not be communicating with the pcm

It takes 60-68
Psi of fuel pressure on this engine, 30
Psi may seem like plenty at the test port.. but it is not enough to spray like it should through the injectors

 

[SKW1020]

First check spark plugs
How do they look?
You can do a simple test and test for spark

If you have a check engine light and it goes off when cranking
And you have a theft light that flashes and then goes out while cranking it is not likely a pcm

Check those two lights
So the basic tests are check for spark
Check for fuel pressure
Check battery voltage
Then a visual inspection of the engine and fluids, filters.. no mouse house in the airbox, no large leaks, nothing disconnected
All fuses must be checked all of them
A fuse can be good and not be seated fully or not seated in the correct spot
The blades can have corrosion on them

After this it’s a compression test
The radio power situation is odd

There is no reason a scanner should not be communicating with the pcm

It takes 60-68
Psi of fuel pressure on this engine, 30
Psi may seem like plenty at the test port.. but it is not enough to spray like it should through the injectors

This all makes sense, except for the fact that it ISNT cranking.... the no crank kind of makes this list a non issue doesn't it? All of these things have been checked except for compression. Is the radio issue odd? I dont know.... I never noticed if cranking the key took power from the radio before....

 

[SKW1020]

First check spark plugs
How do they look?
You can do a simple test and test for spark

If you have a check engine light and it goes off when cranking
And you have a theft light that flashes and then goes out while cranking it is not likely a pcm

Check those two lights
So the basic tests are check for spark
Check for fuel pressure
Check battery voltage
Then a visual inspection of the engine and fluids, filters.. no mouse house in the airbox, no large leaks, nothing disconnected
All fuses must be checked all of them
A fuse can be good and not be seated fully or not seated in the correct spot
The blades can have corrosion on them

After this it’s a compression test
The radio power situation is odd

There is no reason a scanner should not be communicating with the pcm

It takes 60-68
Psi of fuel pressure on this engine, 30
Psi may seem like plenty at the test port.. but it is not enough to spray like it should through the injectors

When I use my friends scanner, high dollar one, it connects to things, but cant connect to the pcm. Here are the messages from his scanner. B1352 and B1359 look really meaningful to me. When I ran this test, it told me to verify that I had the key in run position THREE TIMES... it did not recognize that I had the key in run position. Is this not the issue?

 

[SKW1020]

When I use my friends scanner, high dollar one, it connects to things, but cant connect to the pcm. Here are the messages from his scanner. B1352 and B1359 look really meaningful to me. When I ran this test, it told me to verify that I had the key in run position THREE TIMES... it did not recognize that I had the key in run position. Is this not the issue?

View attachment 463766

View attachment 463767

View attachment 463768

The key thing to me is that it didn't know that I had the key in and in the run position...... I realize that these two codes have something to do with the door dinger being taken out, so what could/would make the scanner not see that I had the key in run position

 

[410Fortune]

No power at the obd2 port would make the scanner think the key is not turned