Hello,

I have a strange issue where after replacing the alternator, all connections look to be proper, as soon as the ignition switch is turned on I have the engine control fuse popping.

Some have pointed at a faulty PCM regulator, but I thought that just regulates the voltage once the car is actually running.

Are there any specific tests I can do to perhaps track down a faulty ground or ??

I have looked through some other threads doing a simple google search but came up empty on a process for testing.

Could use some assistance on this one, and Thanks in advance.

 

Take the alternator to the parts store, have it tested. (off the truck.)

Charge the battery up good, does the fuse blow with alt disconnected? If not, alt is likely bad. (yeah, I know, its 'new'. Doesn't matter. Wouldn't be the first part I have seen that was bad right out of the box.

 

Thanks for the speedy suggestion!

I suppose it's just as easy to disconnect the power cables from the alternator and try to see if the fuse blows?
I can certainly try that first and see what the outcome is.

Let me try that first and take it from there.

 

careful where you put the wires, some of them will still be hot. (as in: Powered.)

 

Indeed! The current she be flowin still...

 

Okay I went ahead and disconnected the alternator, and I put the key in ignition and put it in the ACC position. As soon as that was done the Engine Control Fuse popped. I then decided to try some other things. Here is what I tried:

1) I disconnected the PCM and noticed that if I disconnected this plug on the PCM, the engine control fuse woud not pop.
2) Additionally on the PCM plugs starting from left to right, if i unplugged the plug to the far left on the PCM (colored black), the fuse would not blow even if i left the middle and right plug plugged in.

Could use some additional insight in diagnosing the issue.

 

If you don't have a service manual for your truck yet, get one from here. Wiring diagrams are in section 8W. Find which wires that fuse supplies power to, and trace them from the PDC, to PCM. (and anywhere else they go.) Gotta be a short somewhere.

 

RESOLVED! :

@HeyYou, Thank You for your assistance, and pointing me to the service manual with the electrical diagram. First and foremost, I want to thank you because this truck was actually for sale, and I drove from Beaverton Or. to Grant's Pass to go get it. All under the premise it didn't start due to the Engine Control Fuse blew.

Here is how I solved the problem and hope that it helps others:

1) Disconnect negative/positive cable from battery (repeat for each test)
2) Disconnect the PCM and see if the fuse blows - in my case it did not (I did this by turning key to ACC position)
3) Reconnect PCM

4) At the fuse box (PDC) in engine bay, disconnect the ASD Relay. (In my case the fuse did not blow)

This is where I went to the Electrical diagram and noticed that the ASD relay, and the PCM had a wire in common ALONG with the fact that each of the injectors shared the same colored wire. - Green with Orange stripe.

5) Remove intake manifold (it obstructs access on passenger side to injector plugs) and disconnect each of the injector plugs and analyze.

6) I then started with the PCM plugs and looked for any blowing of the fuse - so far so good.
7) Then each of the injector plugs and noticed one had the rubber grommet inside it was seperated. I fixed it and kept plug in each one and retesting.
8) I did this for all plugs and no longer had any issues with blowing a fuse.
9) I then reinstalled the manifold, and any thing else not connected and....
10) Start car...I must have gone through at least 10 fuses before I went through these steps or the diagram. I highly suggest going through the electrical diagram!! - The truck started...after 1 year of people scratching their heads!

I drove the truck back 250 miles and still noticed that the voltage was still high, and a strange high oil pressure issue. Today I resolved the issue with the voltage issue by installing an external regulator (I bought the kit available on the internet). The high oil pressure issue is still a mystery and i'll post another thread on it.

Hope however this helps someone track down their own issues.

 

Awesome. You are going to LOVE the truck. (but hate the fuel 'economy'..... )