Truck won't crank

[Doubeleive]

I had checked concerning the fuse box. Looks all normal without moisture or green crust...

might want to check all fuses and inspect any related sensors/relays i.e.
I think you can rule the pcm it's self out now though since you got the same results with a known good one.
maybe try unplugging the noted sensors below and see if it will crank, that's easy enough to do just have buy a box fuses lol
but one of the associated sensors could be visibly bad, maybe. a meter will probably be necessary to say for sure

A blown PCM B fuse on a GM 1500 truck (or similar vehicle) usually indicates a short circuit or excessive current draw in a circuit powered by that fuse. The PCM B fuse typically protects circuits related to the Powertrain Control Module (PCM), but the exact circuits can vary slightly by model year and specific vehicle. It's crucial to consult a wiring diagram specific to your truck's year and model for accurate information.

Here's a breakdown of common causes:

1. Short Circuit in Wiring:

• Damaged Wiring Harness: This is the most frequent culprit. Rubbing against engine components, sharp edges, or general wear and tear can damage the insulation of wires, causing them to short to ground. Look carefully around areas where the harness bends or is close to hot or moving parts.
• Loose Connections: A loose connection can sometimes cause a short or intermittent contact, leading to a blown fuse. Check connectors related to the PCM and any sensors or components powered by the PCM B fuse.
• Rodent Damage:Mice or other rodents can chew on wiring harnesses, creating shorts.

2. Faulty Components:

• PCM Itself: A failing PCM can sometimes draw excessive current, blowing the fuse. This is less common than wiring issues but is still possible.
• Sensors: A shorted sensor (e.g., oxygen sensor, mass airflow sensor, etc.) can also cause the fuse to blow.
• Actuators: A shorted actuator (e.g., idle air control valve, fuel injectors, etc.) can also be the problem.
• Relays: While less common, a shorted relay coil can also cause this issue.

3. Other Issues:

• Overloading the Circuit: Although less likely, if something has been added to the circuit that draws too much current (e.g., aftermarket accessories incorrectly wired), it could overload the fuse.
• Water Intrusion: Water or moisture in connectors or wiring harnesses can cause shorts or corrosion, leading to blown fuses

 

[Doubeleive]

like for instance if a 02 sensor harness was melted on the exhaust or got frayed, etc...
you have to careful when giving other vehicles a jump, improper feedback can fry things on your side.

 

[nonickatall]

I guess I have found the problem. I pulled the fuel pump relay and now the fuse stays and the truck cranks...

I will swap the fuel pump, then I will see what's happen.

 

[Doubeleive]

I guess I have found the problem. I pulled the fuel pump relay and now the fuse stays and the truck cranks...

I will swap the fuel pump, then I will see what's happen.

while you are under there inspect the fuel pump harness where it feeds forward make sure it's not rubbing on the frame or body anywhere, just to be on the safe side.

 

[nonickatall]

I have removed the tank. Looks crazy. Harness seems to be ok...

Now I try to open the ring from the fuel pump...

 

[Doubeleive]

ugh that's a lot of rust monster....... man I would put some kind of coating on the new one before you slap it back up under the body

 

[Scottydoggs]

well now, that pump owes you nothing. found that pesky fuel leak too.

 

[nonickatall]

The pump is out, but now I have the problem that two connections can no longer be removed. Does anyone know if these connections are available separately or do I have to buy the hose separately?

 

[Doubeleive]

The pump is out, but now I have the problem that two connections can no longer be removed. Does anyone know if these connections are available separately or do I have to buy the hose separately?

i'm guessing that your going to have to try and spray those with something and try to work them out carefully.
similar to what happens with the heater hose-t's that everyone claims can just be pulled off haah, not....after years of being hermetically sealed

 

[Tonyrodz]

I wonder where all that rust came from. You guys use salt on the roads in the winter?

 

[nonickatall]

Yes, in Germany they use a lot of Salt in the winter..

 

[Tonyrodz]

Yes, in Germany they use a lot of Salt in the winter..

Same here in the northern and north eastern states. Do you know where in the states your Escalade came from? Just curious if your rust issue started here in the US or if it started in Germany.

 

[rockola1971]

Makes sense now according to attached schematic they are using PCM B fuse also to power the Fuel Pump via the Fuel Pump Relay. Wonder why GM did away with the previous individual Fuel Pump Fuse.

 

[Fless]

@89Suburban were you the one who used something like the ones that come with 18" of fuel line and a splice?

I think these are the ones:

Connectors only: Dorman 800-080 (5/16") and 800-082 (3/8")

Connectors with pigtail: Dorman 800-058 (3/8" with 18" fuel line) and Dorman 800-057 (5/16" with fuel line)

 

[nonickatall]

Same here in the northern and north eastern states. Do you know where in the states your Escalade came from? Just curious if your rust issue started here in the US or if it started in Germany.

My car is a European model and was delivered directly to Germany.

Fortunately, the underbody of my car was protected against corrosion early on and is in relatively good condition. But they probably didn't do anything to the fuel pump.

I'm annoyed because I've wanted to do the underbody for two years but never had the time. People's own cars are always the worst treated.

 

[nonickatall]

Makes sense now according to attached schematic they are using PCM B fuse also to power the Fuel Pump via the Fuel Pump Relay. Wonder why GM did away with the previous individual Fuel Pump Fuse.

Thank you very much for your help anyway. It gave me the crucial clues. I haven't really solved the problem yet, because the wiring harness looks OK and the fact that petrol leaked from the petrol pump shouldn't have caused an electrical fault.

But since the fault hasn't occurred since I pulled the petrol pump relay and the petrol pump was leaking and causing problems anyway, I think the connection is clear.

I'll need a few more days because I'm now doing the rust protection on the underbody at the same time, but I think I'll briefly hook the petrol pump up to the wiring harness today and just start the car with the petrol pump relay to see if the fuse stays intact.

In any case, you've helped me a lot...
Best regards from Germany

 

[rockola1971]

My car is a European model and was delivered directly to Germany.

Fortunately, the underbody of my car was protected against corrosion early on and is in relatively good condition. But they probably didn't do anything to the fuel pump.

I'm annoyed because I've wanted to do the underbody for two years but never had the time. People's own cars are always the worst treated.

Here in the states its a known problem that "rustproofing" ultimately causes moisture to be trapped between the coating and the metal which ends up looking like your fuel pump module top. Its well hidden under the coating until the rust expands enough to start cracking the coating and chunks start to fall off.

 

[nonickatall]

@89Suburban were you the one who used something like the ones that come with 18" of fuel line and a splice?

I think these are the ones:

Connectors only: Dorman 800-080 (5/16") and 800-082 (3/8")

Connectors with pigtail: Dorman 800-058 (3/8" with 18" fuel line) and Dorman 800-057 (5/16" with fuel line)

Thank you very much, that helps a lot. I will check today where I can purchase these in Germany.

 

[rockola1971]

Thank you very much for your help anyway. It gave me the crucial clues. I haven't really solved the problem yet, because the wiring harness looks OK and the fact that petrol leaked from the petrol pump shouldn't have caused an electrical fault.

But since the fault hasn't occurred since I pulled the petrol pump relay and the petrol pump was leaking and causing problems anyway, I think the connection is clear.

I'll need a few more days because I'm now doing the rust protection on the underbody at the same time, but I think I'll briefly hook the petrol pump up to the wiring harness today and just start the car with the petrol pump relay to see if the fuse stays intact.

In any case, you've helped me a lot...
Best regards from Germany

That fuse powers through the contact set of the fuel pump relay straight to the fuel pump. It could be the pump is shorted (Its motor windings melted together which lowers resistance and increases current draw)*NOTICE* I did NOT say short to ground for the pump or you have a wiring harness short to ground fault. Go to both contact terminals and measure to ground to check for a short to ground (with pump disconnected).

 

[nonickatall]

Here in the states its a known problem that "rustproofing" ultimately causes moisture to be trapped between the coating and the metal which ends up looking like your fuel pump module top. Its well hidden under the coating until the rust expands enough to start cracking the coating and chunks start to fall off.

I use Fluid Film and Permafilm to protect the car. That has the advantage, that you have a fluid material under the coating, so that when the coating gets cracks it does not really bring problems. I have very good experience with that material in the past decades.

But since 2 years when I bought the car I was want to do that.

I had to do some work at the front end because my front wheel bearing hubs were broken and I was protecting the front, which is absolutely free from rust, but the rear end I struggled because if to many of work and a divorce between...

But as I always say: Sometimes you lose and sometimes the others win...