Thanks Darin.
I had the emergency brake braket off looking for grounds by the PCM. There was one ground but it wasn't associated with PCM. I'll check the other grounds. I did replace a couple of those as I recall.
On the IDM relay, at 6 oclock position is that the ground for the IDM relay switch?
I have not checked that.

 

The PCM shouldn't be able to send 1.36 volts to the GP relay, and regardless of what the GPR is doing, it cannot, IMO set the a check engine light (CEL). If your CEL is on, you have codes stored and we are grasping at straws guessing at problems until you get those codes and put them up here. It may be something as simple as a bad Engine Oil Temp sensor or something like that. The PCM uses these sensors to determine engine temperature and whether to keep the GP's running or not. Get those codes read and we can surely help you with this problem Until we have the codes, we are just guessing.

In regard to the grounds, there are several grounds you need to look at. There is one right above the IDM in the engine compartment, it goes into the inside of the driver side fender. There is also the larger one going into the core support between the core support and the driver side battery. I believe there is also one around the area of the heater core, again on the inside of the engine compartment. Regardless of whether the grounds you are checking are related to the PCM or not, you should check them. The way the electrical systems in these trucks are designed, they use the ground from one device in many cases as a signal path for something else.

As far as the 1.36 volts reading on your multimeter goes, I am guessing that is what it reads when one side is connected to a 12v source and the other side is connected to an open ground (connected to a wire going nowhere).

 

PCM has four power grounds .. pin 25, 76, 77 and 103. Ohm each out to the drivers side radiator support bracket "major ground" and to battery ground. Pin 25 is grounded to the fender, which I believe is the black wire.

PCM does not supply voltage to the IPR or GPR, instead it pulls those lines to ground to activate. When it does pull those lines to ground it should measure somewhere around 0.25 volts, not 1.36 volts. So either your volt meter is reading wrong, you have a bad ground somewhere or the PCM is causing the issues (doubtful) .. my guess it to check those grounds first.

 

Thank you guys for the procedures. I have been scratching my head trying to figure out what to do next.

 

GET THE CODES as mentioned

 

Here is what I found.
Darin: Pin 70 of PCM connector to 6 oclock position on IDM relay: OHMS: <2

Jim: All four of those pins ohmed out at <2 when connected to the ground by the radiator.

 

One other thing:
There are two sets of black connectors under the master cylinder and another set of connectors, one is black and one is grey. What do they go to?
I think one is the transmission and the other set is the towing lights, right?

 

One is under hood light and the other is CC

 

I'm not sure but think the wire shown in the picture below is a PCM ground ...



And the picture below is a major ground point behind the drivers side battery ...

 

I was checking the voltage again at the glowplug connector and when you first turn the key on (glowplugs are cycling) the voltage is nil, but after the glowplugs go off the voltage goes up to the 1.3. I don't know what to make of that.
The ground in the first picture comes off pin 102.

 

What glow plug connector are you looking at? The actual UVCWH at the GP?

 

It is the small little 2 pin wire connector that comes off the glow plug relay.

I had the codes read this afternoon"
1280
235
472
1211
198
113
603
I know some of these codes are because I ran the truck with the sensor unplugged to see if it would make a difference in performance.
The guy who read the codes said the IPR duty cycle at idle was 16%. He thought that was a little high and suggested it may be a problem with the IPR or ICP. I put a new IPR in along with a new pigtail, but did not change the ICP. He thought it idled better when we unplugged the ICP.

 

Such a long thread, it's been forgotten -- is this a California truck? Can you post a pic of the connector? What colors are the wires on that connector?

 

Yes, it is a california truck.
one wire is red/green stripe
the other is pink/orange stripe. (what it looks like anyway.)

 

Okay, this time try the following two tests with the meter:
1) Set the meter to DC Volts, put the red probe on the red/green terminal, and the black probe to a good ground (battery negative) -- NOT to the other terminal. Turn the key to RUN. You should get 12(-ish) volts. If you don't, then the problem is with the incoming power to the coil circuit of the relay. Thing is, that's energized by the same fuse as what powers the PCM itself, the famous maxifuse 22. So if the WTS light is coming on, that fuse is good, and there's a break in the wire between that fuse and the relay.

2) Set the meter to resistance or continuity, put one probe on the pink/orange terminal and the other on a good ground. With the key off, it should read infinite resistance. Turn the key to RUN. It should read near-zero resistance, and/or the continuity beeper should beep. It should remain that way as long as the PCM expects to cycle the GPs (stone cold, probably about 2:00).

Do these things with the connector unplugged, so the relay itself doesn't confound the tests.