Needing help with PCM connectivity 01 ST

[410Fortune]

Start relay trigger / circuit goes key tumbler to ignition switch through clutch pedal jumper through neutral safety circuit at dtrs (side of transmission) then to start relay

PCM relay power trigger/ circuit goes from key tumbler through ignition switch through fuse 19 interior through power diode (under hood fuse box) then to trigger to eec/pcm relay

Power for the eec relay goes through battery wires through eec fuse and to relay

Power for start relay is similar except the ground for the relay comes from pats / theft module

 

[SKW1020]

Does check engine light up with key on?

Check pcm relay

No CEL light with key on, volts on pcm relay with key in run position is 12.3. And im pretty sure I dont hear the fuel pump running, yet the fuel pump relay is getting power. It may bear repeating that when I put my friends Autel Diag on it, when I would run a test, it would tell me three times to make sure that I had the ignition on, as if it wasn't, however, it was and I think this is where the problem is somehow or another. Once the test would eventually run, I got these codes:

B1352 Ignition in circuit fault
B1359 Ignition Run/Accessory Circuit Failure

I am sure this can be figured out, just unclear how yet lol... I appreciate you guys' help

 

[SKW1020]

Start relay trigger / circuit goes key tumbler to ignition switch through clutch pedal jumper through neutral safety circuit at dtrs (side of transmission) then to start relay

PCM relay power trigger/ circuit goes from key tumbler through ignition switch through fuse 19 interior through power diode (under hood fuse box) then to trigger to eec/pcm relay

Power for the eec relay goes through battery wires through eec fuse and to relay

Power for start relay is similar except the ground for the relay comes from pats / theft module

Well, knowing that flow chart, (thank you for making sense of the visual version!) could this error be significant?

P0500 VSS sensor circuit fault

In addition to the ignition CMDTC's, this was also in the list. Not sure if it could affect the thing not cranking or not.

 

[410Fortune]

Vss is in the rear axle on a 2001 and the wires from it run directly to the abs module
The abs module then takes the 17000 pulses per mile generated by the vss and sends it over to the computer… the computer then changes it or “buffers” the signal to 8000 ppm which is then sent to the instrument cluster, gem module (4wd shift computer) and the cruise control

Interesting that you got a code from the pcm!
Is the scanner again talking to the computer?
I wonder if the computer is ok

 

[SKW1020]

Vss is in the rear axle on a 2001 and the wires from it run directly to the abs module
The abs module then takes the 17000 pulses per mile generated by the vss and sends it over to the computer… the computer then changes it or “buffers” the signal to 8000 ppm which is then sent to the instrument cluster, gem module (4wd shift computer) and the cruise control

Interesting that you got a code from the pcm!
Is the scanner again talking to the computer?
I wonder if the computer is ok

The Autec Diag when hooked up to this vehicle, says it cant connect with the PCM at all. I am not sure if you saw where I stated that I have another sport trac in my driveway that will start, so all components are available to me to switch out on the one that wont start. I have physically taken the pcm and ignition from the working Sport trac and put them in the problem Sport trac and no change, as if I hadn't switched anything out at all

 

[SKW1020]

Vss is in the rear axle on a 2001 and the wires from it run directly to the abs module
The abs module then takes the 17000 pulses per mile generated by the vss and sends it over to the computer… the computer then changes it or “buffers” the signal to 8000 ppm which is then sent to the instrument cluster, gem module (4wd shift computer) and the cruise control

Interesting that you got a code from the pcm!
Is the scanner again talking to the computer?
I wonder if the computer is ok

When you say computer do you mean the PCM? Or is the computer something other than the pcm?

 

[410Fortune]

PCM /eec / computer all same thing sorry for any confusion

Your two sport tracs make me feel right at home

So did you also change the pats module from behind the passenger airbag?

With the 2001 (job 1) sport tracs the pcm, pats security key, and pats module behind the airbag all just stay together as part of the security system

It gets tricky here because in 2002 (job 2) they switched to a different pats and no more module

Does the aux power point in your center console have power?

If you can’t connect to the computer and you try two different computers then it is either a power issue for the obd2 port or a wiring issue between the truck and computer

 

[SKW1020]

PCM /eec / computer all same thing sorry for any confusion

Your two sport tracs make me feel right at home

So did you also change the pats module from behind the passenger airbag?

With the 2001 (job 1) sport tracs the pcm, pats security key, and pats module behind the airbag all just stay together as part of the security system

It gets tricky here because in 2002 (job 2) they switched to a different pats and no more module

Does the aux power point in your center console have power?

If you can’t connect to the computer and you try two different computers then it is either a power issue for the obd2 port or a wiring issue between the truck and computer

Ok, the one I'm trying to fix, is the 2001. The one that I bought for body parts is a 2003. So maybe thats why switching the pcm and ignition didn't jive. I do have power in the center console.

 

[410Fortune]

You can’t do that
01 and 03 pcm not compatible!
The pats system is completely different
Go back to the 01 pcm key and tumbler

 

[SKW1020]

You can’t do that
01 and 03 pcm not compatible!
The pats system is completely different
Go back to the 01 pcm key and tumbler

Fair enough....I was just hopeful that they might be interchangeable. So how can I check the pcm and tumbler on the 01?

 

[410Fortune]

So your 2001 sport trax with patsnsecirity type b
The pcm, chip key, and pats module (behind glove box) must all be from the same vehicle

This is why we ask if the theft light flashes normally and then goes out when you turn the key to start. If the light goes out this means the pcm and pats module are happy with the chip key

When I convert these trucks to v8 I often have to replace the pcm, the key and tumbler, and the pats Module with ones from the donor v8 truck.

So I would go back to your 01 pcm, key / tumbler and make sure the pts module is still there … then check the theft light


If the theft light does not go out and instead it rapid flashes… then you have a pats issue

 

[SKW1020]

So your 2001 sport trax with patsnsecirity type b
The pcm, chip key, and pats module (behind glove box) must all be from the same vehicle

This is why we ask if the theft light flashes normally and then goes out when you turn the key to start. If the light goes out this means the pcm and pats module are happy with the chip key

When I convert these trucks to v8 I often have to replace the pcm, the key and tumbler, and the pats Module with ones from the donor v8 truck.

So I would go back to your 01 pcm, key / tumbler and make sure the pts module is still there … then check the theft light


If the theft light does not go out and instead it rapid flashes… then you have a pats issue

The 2001 has all original pats, key and pcm. Never has had an issue with these things. Still doesnt. No abnormal flashing theft light. All seems to be happy with that system. In my mind, its somewhere between the ignition and the pcm... some wire grounded out or such. I say this because the autel diag cant see the pcm, and when I do a test with it, it tells me three times to make sure the key is in ignition and in run position.... it cant see that the ignition is on, What could cause that?

 

[410Fortune]

The pcm not being powered up
Or an issue with the can bus + and - wires from ob2 port to the pcm
Have probably asked this before but let’s go over it again

The check engine light comes on when you first turn the key
You can hear the fuel pump run for a second

The check engine light goes off when you turn the key to start?

 

[SKW1020]

The pcm not being powered up
Or an issue with the can bus + and - wires from ob2 port to the pcm
Have probably asked this before but let’s go over it again

The check engine light comes on when you first turn the key
You can hear the fuel pump run for a second

The check engine light goes off when you turn the key to start?

No check engine light in run or start position, cant hear fuel pump run at all. Attaching a photo of OBDII port voltages with the key in the run position.

 

[SKW1020]

The pcm not being powered up
Or an issue with the can bus + and - wires from ob2 port to the pcm
Have probably asked this before but let’s go over it again

The check engine light comes on when you first turn the key
You can hear the fuel pump run for a second

The check engine light goes off when you turn the key to start?

Can bus is a new term for me, but this seems like the right tree to bark up... in my mind anyway... is there some way for me to know what voltages to look for on the PCM? And where to find those voltages? But hey, I dont mind doing all 104 lol if it helps me figure it out.

 

[410Fortune]

Okay!

Can bus is like usb connection
In a car it has two wires
Can bus + and -
Basically these wires go directly from the obd2 port to the pcm, they also go to the gem module pats module and others
The ones you are concerned with are from obd port to pcm

Here is the wiring for the obd2 connector

Scp bus + and -
Then constant power, aux switched power and ground
ISO is communications from body modules like gem abs etc

 

[410Fortune]

PCM

 

[410Fortune]

The communication wires pass through (basically all dash to engine bay wires pass through) the 3 bulkhead connectors under your brake booster… then most dash to ocm/ drivetrain wires also pass through the big 42 pin square connector at the back of your intake, c115

 

[410Fortune]

I would start with a simple continuity test if the scp bus wires + and - from obd2 port to the pcm connector
(Pins 15 and 16)


Verify ground at pins 24 and 25 and 51 and 103
Then you can verify you have power at the pcm connector with the key off
Pin 55 keep alive power

and then with the key on
Pin 71 and 97

Simple Multi Meter tests will tell you a lot!!
Let us know what you find and we can troubleshoot backwards from there

 

[SKW1020]

Okay!

Can bus is like usb connection
In a car it has two wires
Can bus + and -
Basically these wires go directly from the obd2 port to the pcm, they also go to the gem module pats module and others
The ones you are concerned with are from obd port to pcm

Here is the wiring for the obd2 connector

View attachment 463141

Scp bus + and -
Then constant power, aux switched power and ground
ISO is communications from body modules like gem abs etc

Awesome! Then do you know if the voltages I have listed in this pic are correct?