Fuse 28 (pcm1) keeps blowing

#1
Hi all
happy new years !!

just got a 2002 trailblazer 4.2 4 months ago

i was driving 2 days ago and the engine just turned off
all electrical works, the dashboard and all, but truck don't crank,

so i checked my fuses and fuse 28 ( PCM1 ) was blown
i replaced it, the truck cranked, turned on for a second and shuts down
PCM fuse blew again

I watched a video on youtube about some guy who says that most of the time is the fuel pump who shorts or the fuel pump cable

So i removed the fuel pump relay ( micro relay 41 ), replaced PCM1 fuse ( fuse 28 ) and the fuse don't blow

That leads me to think is the fuel pump,
is there any more tests i can do?
fuel pump is around 140 to 300
i do not want to buy one, replace and find out that is something else

Thanks
Rolo
 

MRRSM

Lifetime VIP Supporter
#2
Welcome to GMT Nation @rolo95...

FIRST THINGS FIRST...

CHECK THE GROUND CABLES/WIRES... Starting with the Ground Cable that BOLTS TO THE ENGINE BLOCK... Then anything that Grounds to the Chassis in the Engine Compartment and the Bonding Straps attached to the Firewall... and any other places that maybe you were working on and accidentally bumped loose.

Also... If you look along the Underside of the Dashboard along the Console Floor side area of the Passenger Side of the Cab... You'll find a very important Black SPLICE BLOCK GROUND that should be Bolted to the Fire Wall with a Small Fastener.... unscrew-unbolt that Fastener and CLEAN any Rust or Corrosion off and then re-connect THAT Ground location. As shown in THIS Video after you Click on the underlined link to his Youtube Channel:


Now try and Start the Engine.

Next...

Testing the Fuel Pump System…


Replacing the Fuel Pump (If Necessary…) NO CHEAP ONES....ONLY USE ACDELCO, DELPHI OR BOSCH!!!

 
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TequilaWarrior

Well-Known Member
#5
If I remember correctly, I had the same exact behavior and got severely frustrated trying to troubleshoot it. I eventually dropped the tank and found that the pigtail to the fuel pump/sender had at some point in the past shorted (it was burnt looking) and the lock on the plug had broken off. This caused the plugs to separate enough to not only cause arcing, but give intermittent continuity and a huge amp draw blowing the fuse. I DID replace the fuel pump/sender, cleaned all connections, plugged the pigtails back together being sure to apply bulb grease to the plugs and ziptied the plugs together to prevent their separation.
The other symptoms I had: no fuel pump sound or "jittery" fuel pump sound immediately preceding a blown PCM fuse and fuel gauge not working 90% of the time and never correct above half a tank.

What's your fuel pump sound like?
What's your fuel gauge doing?
 
OP
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#7
If I remember correctly, I had the same exact behavior and got severely frustrated trying to troubleshoot it. I eventually dropped the tank and found that the pigtail to the fuel pump/sender had at some point in the past shorted (it was burnt looking) and the lock on the plug had broken off. This caused the plugs to separate enough to not only cause arcing, but give intermittent continuity and a huge amp draw blowing the fuse. I DID replace the fuel pump/sender, cleaned all connections, plugged the pigtails back together being sure to apply bulb grease to the plugs and ziptied the plugs together to prevent their separation.
The other symptoms I had: no fuel pump sound or "jittery" fuel pump sound immediately preceding a blown PCM fuse and fuel gauge not working 90% of the time and never correct above half a tank.

What's your fuel pump sound like?
What's your fuel gauge doing?
Tequila :
i haven't check it on those sounds, i will hopefully today,
what you mean by truck pump sender, any pics?

your truck is fine now ?

----------------------------------
what do you guys recommend to remove the fuel from the tank, any electrical or mechanical hand pumps?

if want to lower the fuel tank so i need to remove at least like 16 gallons of fuel
wash/clean the fuel tank and put a new fuel filter as well and remove the fuel pump and inspect
the electricals inside, i have seen some guy on youtube who showed melted fuel pump internals
where the electrical supply cables go into the body of the pump

I filled my truck fuel tank and i was going out of town and the truck died on me
at the last gas station of my town, phwewwww i was lucky that the truck doesn't die on me 100 miles down the road in the middle of nowhere

also, where i can get the complete electrical schematics for the 2002 TB
also i will do a coil check, maybe one of the coils is bad ? but how come that removing the fuel pump relay prevents the fuse#28 to blow, mmmmm.... that means its not the coils right ?
if it was a coil, regardless i remove the fuel pump relay it must still blow.

Rolo.
 
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#8
If the in-tank pump runs, disconnect the fuel line at the engine, find a fitting that would fit in there and jump the relay. That would also show if the pump is responsible for the high amperage draw blowing the fuse.
 

MRRSM

Lifetime VIP Supporter
#9
If the Fuel Pump cuts off or perhaps has hidden sparks from shorting out on top of the tank just before that 15 Amp Fuse burns out... turn the Ignition Key to the Off Position and using either a few Plastic 5 Gallon Gas Containers on hand or better yet... another vehicle ... you can safely Transfer-Pump most of the contents of your present Fuel Tank directly into the alternate Tank using this Method:

https://gmtnation.com/forums/threads/de-fueling-no-fooling.17840/


If fumes/vapors are also in evidence from under the driver's side of the vehicle... having a decent ABC Fire Extinguisher at the ready nearby is a good idea.
 
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TequilaWarrior

Well-Known Member
#10
Tequila :
i haven't check it on those sounds, i will hopefully today,
what you mean by truck pump sender, any pics?

your truck is fine now ?

----------------------------------
what do you guys recommend to remove the fuel from the tank, any electrical or mechanical hand pumps?

if want to lower the fuel tank so i need to remove at least like 16 gallons of fuel
wash/clean the fuel tank and put a new fuel filter as well and remove the fuel pump and inspect
the electricals inside, i have seen some guy on youtube who showed melted fuel pump internals
where the electrical supply cables go into the body of the pump

I filled my truck fuel tank and i was going out of town and the truck died on me
at the last gas station of my town, phwewwww i was lucky that the truck doesn't die on me 100 miles down the road in the middle of nowhere

also, where i can get the complete electrical schematics for the 2002 TB
also i will do a coil check, maybe one of the coils is bad ? but how come that removing the fuel pump relay prevents the fuse#28 to blow, mmmmm.... that means its not the coils right ?
if it was a coil, regardless i remove the fuel pump relay it must still blow.

Rolo.
This was probably 7/8 years ago, so my memory was a little foggy. BUT, I believe the fuel pump and the fuel level sender share a single ground and share a single plug that gets connected at the pump/sender assembly. I replaced the entire assembly - it wasn't worth it to me at the time to drop the tank and troubleshoot before acquiring a new pump/sender assembly. I had help and wanted to make the most of it at the time. My buddy was the one who noticed the burnt wires. Obviously, sparks & high amp draw around fuel vapor is not good. Have an ABC extinguisher handy whenever you do anything with fuel. I'm confident it's not your coils. There are guides and videos here at gmtnation that will walk you through dropping the tank - make sure you count the number of connections you have disconnected on the tank before dropping it all the way. I snapped off the vent solenoid (I think that's what it was) and ended up having to replace it after fishing the nipple out of the tank (not fun!). Check your filler neck if/when you drop the tank as well, they have a habit of rusting like crazy. Make sure you grease all the electrical connections to the tank - it spends its entire life in the worst possible place, under your vehicle exposed to water, grit, and salt. Seven years after replacing the pump/sender and ziptieing the sender/pump pig tail and I still haven't had any issues. I was fortunate that mine finally quit while I had only a few gallons in the tank - but the transfer methods mentioned earlier are very good options. Just make sure you use a "fuel safe" method and tools.
 
#11
Just be aware that you won't be able to snake a hose into the tank through the fuel filler because of the anti-rollover valve. It's basically a large ping-pong ball. You might have to drop it full of fuel. You can pump it out once it's on the ground with the pump out of it so you can use that hole with a proper tool like what @MRRSM showed.

Yeah, I know. It sucks.
 
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#12
Thanks All for the tips N tricks :wink:

Just be aware that you won't be able to snake a hose into the tank through the fuel filler because of the anti-rollover valve. It's basically a large ping-pong ball. You might have to drop it full of fuel. You can pump it out once it's on the ground with the pump out of it so you can use that hole with a proper tool like what @MRRSM showed.

Yeah, I know. It sucks.
Hey Mooseman
i will try to jumper the pump direct and attach a hose to the engine fuel line
what diameter the hose must be
 
#13
I'm pretty sure you can get a Dorman Help! fitting that would fit in there. Don't know the size.
 
OP
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#14
what i can try is to get those pvc clear hoses a little bit bigger than the actual fit and use a clamp to prevent leaks and try to pump all the gas from the tank manually jumpering the fuel pump at the relay on the fuse box

does somebody know what is the ballpark ohms reading for the fuel pump , i want to use some test leads to stick in to the relay holes to discard a short before jumpering... or i can use those fused base that has leads and stick a fuse so if something is shorted i don't fry my wire harness :wink:
 
#15
When you remove the fuel line from the fuel rail, it's a female end so I don't know how you could do that. You need a male fitting to go in. Even at the fuel filter, you would have the same issue. You could remove the line out of the filter and slip on a hose there.
 
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#16
That sound great, also what i just come up is to cut with a hacksaw a 4" piece of metal line from a scrap out fuel line and use that as a coupler to tap in to the coming fuel line and my pvc hose
hope it works
 

MRRSM

Lifetime VIP Supporter
#17
If you can do so... Please take some close-up images of your work from this point on and Post those views back here ...and if you find and need to replace any lengths of Burned, Compromised Wiring... Amazon has the proper Automotive Grade Wiring for the Job. If needs be... the Re-Wiring Repair can be safely done with the Fuel Tank covered up and removed to a safe location during the necessary Soldering and Heat Shrink work needed to make these Wiring Repairs Safe:

https://www.amazon.com/dp/B01LITJSW2/?tag=elightbars-20

16AWGCOPPERWIREBUNDLE.jpg
 
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#18
Thanks MRRSM

This forum is really active and the best is that people over here are willing to share
their tips N tricks and ways to save some money

For example RockAuto have the bosch fuel pump at 140 right now, my local Chevy dealership have the ACDELCO for 380 @.@ and they dont have it in stock, still havent found the pump as bad, im driving a truck that is not mine meanwile i fix mine, it was raining these past week and temps around 37F , i can't stand low temps very well so i will let the weather catch up a little bit

What heat shrink you recommend and heat gun
also do you have a battery soldering iron recomendation ?
i only have the 120VAC one that you plug in to you wall
so i need to run an extension cord from my wall outlet to where i need to solder
 

MRRSM

Lifetime VIP Supporter
#19
Glad to pitch in and help you, Brother...

One of our Members created this On Topic "How to Solder" Youtube Video. The Best Approach is to get a Decent Complete Kit with enough Power to Heat the Wires when blended together to Melt the Solder and Fuse the electrical link... Permanently. Amazon has a variety of Kits to handle multiple uses for more than just one repair.

The same thing applies with getting Heat Shrink ... Make sure to obtain the stuff that has an Internal GLUE that will melt around and bond around the Repair well enough to prevent the Snow, Slush and Salt Rust from EVER attacking that connection again. If this is your First Rodeo with Soldering.... Practice first on a few Wire Segments and your Kit(s) to get familiar enough to do the repair properly... and safely:


Here are an assortment of Soldering Kits:

AVOID USING EITHER A BUTANE LIGHT OR ANY BATTERY POWERED SOLDERING APPARATUS. iNSTEAD ... OBTAIN A GOOD (14) AWG (American Wire Gauge) Drop Cord LUGGED INTO A 20 AMP Rated Outlet-Socket from the House:

https://www.amazon.com/s/ref=nb_sb_ss_c_1_13?url=search-alias=aps&field-keywords=soldering+kit&sprefix=soldering+kit,aps,219&crid=2BVSW2X1RTR5J&tag=elightbars-20

For Heat Gun and Shrink Wrap Kits... SLIDE THE HEAT SHRINK ONTO THE ONE SIDE OF THE LOOSE WIRES.... FIRST!

Marine Grade Heat Shrink to prevent Wire Bonded Corrosion on top of the Fuel Tank:

https://www.amazon.com/dp/B0125MZ2YE/?tag=elightbars-20

MARINEGRADEHEATSHRINK.jpg

Here are an assortment of Shrink Wrap Heat Guns on Amazon that will suit your Budget:

MAKE SURE THAT THE FUEL TANK AND LOOSE GAS-SOAKED RAGS GET MOVED CLEAR OF THE WORK AREA... AND SEAL OFF ANY FUEL LINES ON THE VEHICLE SO THAT NOTHING CAN GO SIDEWAYS WITH HIGH HEAT FROM THE GUN OR ANY OPEN SPARKS AND FLAMES COMING FROM THE SOLDERING GUN:

https://www.amazon.com/s/ref=nb_sb_ss_i_3_8?url=search-alias=aps&field-keywords=heat+gun+for+shrink+wrapping&sprefix=HEAT+GUN,aps,179&crid=J3R5MJY4PMLZ&tag=elightbars-20

HEATGUN.jpg
 
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OP
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#20
Guys 10000 thanks for your friendship and support
UPDATE :
Today the temp is ok and no rain and some sun
so...
Behold @.@
before removing fuel and stuff i decided to do a test that hasn't done
i replaced the Fuel pump relay with the High beams relay

I did not believe what happened next
truck cranked turned on and the fuse doesn't blow

i let the truck idle for 20 mins and all fine
so i decided to do a test run in the highway
and after 3 miles i feel the vibration of the engine like if a spark plug was not firing
my check engine light turned on ( it was off before and never turned on since the incident)

so i drove to my nearest AutoZone and there was code P0306 2 times
( cylinder 6 miss fire detected )

ASE database says that it can be the spark plugs or the coil
so i want to replace the spark plugs today as they have the originals ( i think )
and the truck has 104k miles

If that does not solve the rough engine i will try to replace the coil
regarding the original symptom what do you guys think?
a shorted wire or pump cannot work well again just by itself, right ?
if a relay shorts, that will blow the fuse?


I am sharing the firing order diagram
that i know 99% have but anyway, i want to give some back of the much i have received in so
little time!
You guys Rock!!

Rolo.

1546720256322.png
 

MRRSM

Lifetime VIP Supporter
#21
Rolo ...That is some Very Good News, Brother...

On the subject of the Coil Pack Issue... around (4) years ago... one of our Senior Members... @Capote ... created a Youtube Video that describes a Test he performed on his "BatBlazer" that is simple and easy to follow for Diagnosing Coil Pack Failure on the GM 4.2L LL8 I-6 Engine:

 
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OP
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#22
Ok, I replaced the sparkplugs
they were like3/4 worn out,
but still same issue, and it was so easy the bat blazer shows!!!
yes, with the engine on there was no change if I disconnect and connect coil #6
I'm buying the coil now
brb
Rolo
 
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#23
So yeah , it was the coil
and now that i have new spark plugs it runs smoother

there is a list of stuff i need to do on my little truck

i need to polish the headlights lens, they are yellowish and cloudy
after that, i want to install LED headlights

i need to clean the throttle body

I need to lubricate the window doors actuators, they move slowly at some points

door electric locks are sticking

the clicking sound i hear when i turn on AC and there is cold air from the dashboard vents that supposed to blow on defrost only

i need to polish the glass on the doors ( all 4 ) they are heavily scratched with vertical stripes

replace the glass door rubber plastic strips that scratched my glass

polish an arc mark on the windshield ( somebody turned on the wipers with worn out blades)

i want to install side steps, wife has a hard time stepping in and out
I will go as time permits

Thanks to all for the help
Cheers
Rolo.
 
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TequilaWarrior

Well-Known Member
#24
Glad to hear you got it fixed. That's one we'll have to remember.

Some notes on headlights: if you polish them, count on polishing them again. I polish mine probably every six months or so. Granted, I don't lacquer mine and I probably should.
Also, the DRL function will kill LED headlights. I thought I beat the system and didn't install a DRL killer thinking LEDs that ran down to 9 volts would be just fine. Turns out the DRL function killed the driver in the LED assembly. I started noticing that some people would move to the right line in a hurry if I came up on them in the left lane. I just thought they were being twitchy - turns out that my low beams began "strobing" after the driver went out in the LED assembly. When I first noticed it, the lights would only do it in DRL mode, but then eventually it did it all the time. Now I'm running halogen lows and LED highs without issue. The color is way off, but the output is fantastic. Eventually I'll go back to LED lows, but only after doing something about the DRL function.

For your vent issues: it may be worth the risk of doing a relearn on the actuators. I forget which fuse #s it is, but, with the car "off" and RAP "off", pull the fuses for HVAC for at least 30 seconds ( I usually go about 2 minutes). Then, reinsert them. Turn the key to "on" without starting the car and your HVAC will come on. I usually turn HVAC off as soon as it comes on for this. Keep the car in "on" (don't start it) and you'll hear the actuators moving. They are relearning their positions - there are encoders in each actuator, that's how the HVAC controller knows how far an actuator is open to "blend" the right temps. Relearn takes around 90 seconds, I just leave it for a few minutes. If you hear loud clicking or grinding, you need to replace an actuator.
 
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#26
Thank you guys for all the info shared here,
hey, it would be a good idea to compile a problems list with the found fixes
example, if your PCM1 fuse keeps blowing, swap the fuel pump relay 1st , if that is not it then keep going with the rest of the procedure, check coils, check injectors, trace the fuel pump wire, check the fuel pump retainer ring and connectors and last pull the fuel pump and inspect for melted and or shorted wires

i replaced my right tail light PCB ( the one who have the 3 lamps ) that thing always get toasted on the top lamp socket as it is always on day and night when you drive the truck

Also, i forgot to add that i need to put some grease on the chassis, it squeaks like an old farm truck

and i need to replace the shocks ( all 4 ) they are gone

As a side note and i think i mentioned that in the opening post
is that the truck is new to me but i just acquired it
from a coworker, he was the second owner, so i am the third
it had 104k miles only , paint is very good , some dings and dents from parking too close to other vehicles, people tend to slam your vehicle on purpose to inflict a ding around here ( that sux ) .
Rolo.
 
#27
We do have some things listed in the FAQ's located in each section that covers the most common stuff but there is no way to cover all issues and fixes. That's when searching is your friend.
 

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