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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29523
Experience:  GM Grand Master Technician 2007. 14 years experience.
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1995 chevrolet k1500 w/at (4l60e) possible wiring ground

Customer Question

1995 chevrolet k1500 w/at (4l60e) possible wiring ground problem?
JA: Have you checked all the fuses? Do you have a wiring diagram?
Customer: yes/yes
JA: What is the model of your '95 Chevrolet?
Customer: k1500
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: wiring
JA: Anything else you want the mechanic to know before I connect you?
Customer: will have to relay to mechanic/trouble shoot
Submitted: 10 months ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 10 months ago.

Hi there, I am Cam.

What exactly is your transmission doing?

Customer: replied 10 months ago.
hi cam...i`m jim
Expert:  GM Tech (Cam) replied 10 months ago.

Hi Jim, so what is going on with your truck/transmission?

Customer: replied 10 months ago.
isnt transmission totally...multi problem/wiring i think...if not a bad ecm
Customer: replied 10 months ago.
lets start when the first trouble started......
Expert:  GM Tech (Cam) replied 10 months ago.

Please, yes.

Customer: replied 10 months ago.
first symptom...possibly unrelated......4x4 blew fuse, then lost power totally to transfer case switch.....ran a stand alone wire to the transfer case switch.....solved that problem, upon next road drive, i noticed converter wasnt locking up...no over drive.....
Customer: replied 10 months ago.
transmission shits perfect...just no lockup. then a few days later i noticed my fuel guage would first work...then not work.........
Customer: replied 10 months ago.
today, i had a check guages light pop on...oil pressure guage said 0 pressure...i pulled over, determined that i did indeed have oil circulating...no knocking or noise at all....
Customer: replied 10 months ago.
the fuel guage always stayed within the range of fuel in the tank...not so now........
Expert:  GM Tech (Cam) replied 10 months ago.

Does your speedo work properly?

Do the brake lights work?

Is there any aftermarket devices installed like a remote starter or such?

Customer: replied 10 months ago.
the oil pressure guage came back up, now registering way high, and fule guage after fill up, does not go all the way to the full mark it always had before, if idilng, touch the gas a lil and fuel guage rises to a higher mark, it responds like the oil pressure guage...up with rpm`s, and down at idle
Customer: replied 10 months ago.
upon noticing the overdrive did not work, cruise controll stopped working as well.
Customer: replied 10 months ago.
i have had the truck 3 years, speedo has always worked at 10 mph fast...no previous problems with it
Customer: replied 10 months ago.
no after markets, let me check tail lights
Customer: replied 10 months ago.
all back lights work properly
Expert:  GM Tech (Cam) replied 10 months ago.

My first thought is a bad ground wire. I would check the grounds down on the frame, check the wiring for grounds on the intake manifold and around the engine bay.
Then I would look at the ignition switch. One feed is for the transmission and such and if that is limiting power, it would cause this.

Test by accessing the thick wires at the ignition switch. With your multimeter set to DC volts, place the red lead on the red wire. With the switch turned on, test the other leads with the black wire. Record the reading and let me know what those are. Repeat the test on the red/white wire. Let me know the results.

Customer: replied 10 months ago.
my exact first thoughts as well...i did find a body to motor ground strap broke...fixed that, no results....oil pressure swtch was previously replaced about 2 years ago...unplugged that, oil pressure and fuel guages went to full readings...have checked the ecm grounds and other grounds on the intake manifold.
Expert:  GM Tech (Cam) replied 10 months ago.

OK so lets look at the power.

Customer: replied 10 months ago.
fuel guage previouly stayed aproxmately stationary when off/starting and run...drops to below E now when turning ign. switch on
Customer: replied 10 months ago.
did you mean...and forgive me...just to clarify...leave the hot lead on the red wire...and probe all other heavy wires with the black leak leaving the hot lead in place?
Customer: replied 10 months ago.
using the black lead to ground, both the red and red/white wires in off had 12.1 volts...running 14.0 volts
Customer: replied 10 months ago.
the yellow has no power in run....tan/white 12.1 red 12.1
Customer: replied 10 months ago.
yellow no power in "on"...not run
Expert:  GM Tech (Cam) replied 10 months ago.

No, the test measure voltage drop over the switch, red probe to red, black to each other power wire.

Customer: replied 10 months ago.
if i follow you correctly...i have the following readings....red ohmn meter lead to red, and black following suit across heavy wires is:tan/yellow -.001....yellow 12.34.....red/white -.001.....brown -.001.....tan/white .029.....tan .018
Customer: replied 10 months ago.
that was on the red wire
Customer: replied 10 months ago.
using the red lead on the red/white wire is as follows....yellow 12.29......red .014...tan/white .014...tan .003...brown .023...
Expert:  GM Tech (Cam) replied 10 months ago.

Those sound right, so I am thinking wiring at the transmission, wiring at the ECM or the ECM itself.

Customer: replied 10 months ago.
The truck does have a replacement ecm...but is the correct fsmilt per gm dealership
Customer: replied 10 months ago.
Family***sorry...cellphone key pad
Expert:  GM Tech (Cam) replied 10 months ago.

Then wiring or connections will be your issue. Finding it could be difficult.

Customer: replied 10 months ago.
Im not sure how old the ecm is...or if its a rebuild
Customer: replied 10 months ago.
To me...there is too many unrelated items going wrong to be much else than the ecm
Customer: replied 10 months ago.
Everything worked fine untill it suddenly started with a blown fuse.
Does this truck have a trans. Module?
Expert:  GM Tech (Cam) replied 10 months ago.

The ECM is the transmission shift module.

Customer: replied 10 months ago.
As i thought
Customer: replied 10 months ago.
I have checked wiring at transmission and transfer case...all the way to the firewall
Customer: replied 10 months ago.
Nothing rubbed or pinched
Expert:  GM Tech (Cam) replied 10 months ago.

OK, did you look at the wiring inside the transmission then?

Customer: replied 10 months ago.
No...what about the guages going wacky?...unrelated issue (my view)...
Customer: replied 10 months ago.
Thats what got me leaning twoards ecm
Expert:  GM Tech (Cam) replied 10 months ago.

Hard to say. IT very well may be related, but with some of these oddball cases, diagnosing over the internet has its limitations.

Expert:  GM Tech (Cam) replied 10 months ago.

Does Tapping sharply on the housing of the ECM change how it runs?

Expert:  GM Tech (Cam) replied 10 months ago.

Or makes it act up or sop acting up?

Customer: replied 10 months ago.
Never tried it...runs well...shifts good...no od...guages act up
Expert:  GM Tech (Cam) replied 10 months ago.

Try tapping and see if it changes anything. IF so, replace the ECM.

Customer: replied 10 months ago.
Will do
Expert:  GM Tech (Cam) replied 10 months ago.

Thanks.

Customer: replied 10 months ago.
my truck is an extend cab 2 door, with the 6 foot box, 5.7 liter (350) engine with 16 inch wheels (285-75-16) what prom code should be in the ecm?...i just want to double check since the truck was bought used...and ecm has been replaced, the speedometer has been 10-12 mph fast since i have had the truck. the current prom code is BJYL...other numbers are: 6075.....1617....4895. i did not drive the truck today to work, so i have not tried rapping the ecm as of yet
Customer: replied 10 months ago.
the rtesearch i have done and can find says it should be a BJYA OR BJYM