Read through the post, check if your theft light is blinking as well when it wont start. Also, check the PCM relay. If the theft light is not blinking, then your issue is different and you should make a new thread.

 

Sorry to all for the lack of updates. It's been cold and snowy/rainy here and I don't have the garage space to work in currently. (one of the reasons the truck went to the shop for the swap in the first place). Anyway, as soon as I have some weather I can work in, I will be diving in to see if I can find the issue with this PCM.

I will be back and post questions or the solution as soon a I can.

 

I'm sure that you have fixed it by now but my 2000 4.6 had a similar stall problem with no DTCs. I turned out to be a cavitating fuel pickup sump. Now I never allow less than 1/2 tank of fuel since it is almost empty by the time the low fuel lite comes on.

 

Ok so I went back outside not that it's not snowing.

Fresh battery, turn the key to start. Get the ----- on the Odometer and the 16 PATS code just like in this video:


#304 relay is supposedly the culprit. However, # 301 ticks rapidly should you try to start the car and slot #302 is empty. Same as the truck in the video.
I'll shoot a few pics for reference.

 

Shop said that they swapped the relays. Not sure about the rapid clicking. (either bad relay or bad source)

Wife pulled #301 (PCM Relay) for us to check.

Just tested the box. Good power and ground to the #304 fuel pump relay. The test is not the same for the PCM relay.

Also, opened up the box to see if there were any issues with the wiring. It all looks solid.
CEL does illuminate when key is turned to "on" position. So, I think the issue is FROM the PCM TO the relay.


I re-installed the relays. Plugged in the battery and turned the key. The dash illuminates and there is what can only be described as a "purring" sound behind the dash/gauge pod- I thought briefly that the fuel pump had primed but it was just purring. Additionally, I noticed that the "battery" icon/light flashes even more rapidly than the theft light. Not sure why. Battery is at 100%.

Also plugged in my OBDII scanner- says connecting. For a moment, I thought it had connected and then it was dead. Unplugged and re-plugged it and said connecting.

 

Any ideas?
This truck has been down quite a while and with uncooperative weather, I am at its mercy. Yesterday sunny and 70*. Today freeze warnings...
Called dealership to see if they could test the PCM if I took it to them. They said no. They need the truck.


Any ideas are welcome.

 

Nobody?

I'm kinda stuck. Electrical is not my forte'

Does anyone have any other ideas I might try before I give up and drag this thing to the dealership? (Which I REALLY want to avoid)

 

 

PCM relay not getting juice.

Fuel pump relay is getting 12v. Without PCM it will not even activate... At least that's what's happening for me.

 

Cool, you're getting somewhere. When you say "PCM relay not getting juice" so you mean the PCM doesn't get 12V to the coil to turn on, or do you mean the 12V+ input supply pin (typically pin 30 common) is not seeing 12V on it?

 

I did a test of the power and ground on the fuel pump relay and I got 12v
I did the same test of the PCM relay and I got nothing.

I disconnected the bolt that affixes the harness to the PCM and everything looks great No corrosion anywhere.
I checked my wires and they all look good.

Not sure where else to test.

 

 

Key ON (engine obviously off since it won't start)

My understanding is that the 5 prongs of the relay are as follows:

#30 is constant battery voltage
#85 is ground
#86 is power to the control side
#87 & 87a are output to whatever is being controlled

Did the following test:

Set multi-meter to 20v. Negative lead to #85 ad positive lead to positive battery terminal. (got constant 12v for the fuel pump relay and nothing for the PCM relay)
Put positive lead to #86 and negative lead to negative battery terminal. (I got 12v for the fuel pump relay and nothing for the PCM relay)

Maybe I'm doing this wrong? Not sure. Electrical is not my strong suit. If anyone can walk me through with baby steps I'll get it eventually. Just kinda stuck and need to get this darned thing up and running.

 

Do you have 12V+ on pin 30? When you turn ignition on, you should have 12V between 85 and 86, thus closing the contact between 30 and 87 or 87a, depending on what is there. If you get 12V on 85 and 86 and 12V is present on pin 30, it's likely a bad relay. If there's no 12V on 85 and 86, something in the control circuit is not switching the relay on. A wiring diagram would help you to find where to go next in that case. You could also try to jump the switching contacts, basically jumping the relay, and see if the PCM wakes up and allows you to start the engine.

 

This English language is so difficult to use to describe what you are actually doing.
Let me take a crack at what I'm envisioning you should be doing.

To check for power on the PCM relay circuit, remove the relay.
Turn the ignition key to the "RUN" position.
Connect the negative lead of your volt meter to the negative terminal of the battery.
Touch the positive lead of your volt meter to the socket where pin 30 of the PCM relay normally goes.
You should see battery voltage on your meter. (If not, verify that the 30A fuse #2 in the BJB (Battery Junction Box) under the hood is good.)

Now touch the positive lead of your volt meter to the socket where pin 86 of the PCM relay normally goes.
You should see battery voltage on your meter. (If not, verify that the 30A fuse #30 in the CJB (Central Junction Box) under the dash is good.)

Now lets check the powers for the fuel pump relay circuit.
With the negative lead of your volt meter connected to the negative terminal of the battery.
With the ignition key in the "RUN" position.
Touch the positive lead of your volt meter to the SOCKET where pin 30 of the fuel pump relay normally goes.
You should see battery voltage on your meter. (If not, verify that the 20A fuse #10 in the BJB is good.)

Now touch the positive lead of your volt meter to the socket where pin 86 of the fuel pump relay normally goes.
You should see battery voltage on your meter. (If not, verify that the 15A fuse #18 in the BJB is good.)

Now, do you have power to all four sockets of these two relays?