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96 suburban electrical problem


cwby94
10-27-2011, 08:49 PM
i got this 96 suburban k1500 LT 2 months ago and now having electrical problem. the volt gauge fluctuates from approx 15 down to 10 and the lights dim almost off and the heater slows way down. i put in new alternator and battery and replaced stock wire from alt to battery + with a 4 ga wire. i cleaned and tightened battery connections and body ground from battery. i took out ALL dash switches to look for loose or bad connections and found none. i found an alpine security system way up inside of dash that i wasn't aware of and have no means of controlling it so i took out all in line fuses that went to the security units. checked wire from battery to starter and got 10 ohms. ...
after start up, length of time varies, the volt gauge will slowly go down until the fluctuations start and if turn on lights or heater then the drop is much faster.

volt meter across battery while running is 14.2 - 14.6.
across battery not running is 12.? ..
the belt isnt new but its tight and its not cracked or frayed

check engine light came on and code reader showed bad #2 heated oxygen sensor. most people tell me this would not be the cause of the electrical problem so i havent changed it yet. the guy that told me to take the fuses out of the alarm system says that the o2 sensor could cause the problem.

i would really appriciate any help with this . Thank you

MT-2500
10-28-2011, 03:39 AM
i got this 96 suburban k1500 LT 2 months ago and now having electrical problem. the volt gauge fluctuates from approx 15 down to 10 and the lights dim almost off and the heater slows way down. i put in new alternator and battery and replaced stock wire from alt to battery + with a 4 ga wire. i cleaned and tightened battery connections and body ground from battery. i took out ALL dash switches to look for loose or bad connections and found none. i found an alpine security system way up inside of dash that i wasn't aware of and have no means of controlling it so i took out all in line fuses that went to the security units. checked wire from battery to starter and got 10 ohms. ...
after start up, length of time varies, the volt gauge will slowly go down until the fluctuations start and if turn on lights or heater then the drop is much faster.

volt meter across battery while running is 14.2 - 14.6.
across battery not running is 12.? ..
the belt isnt new but its tight and its not cracked or frayed

check engine light came on and code reader showed bad #2 heated oxygen sensor. most people tell me this would not be the cause of the electrical problem so i havent changed it yet. the guy that told me to take the fuses out of the alarm system says that the o2 sensor could cause the problem.

i would really appriciate any help with this . Thank you

You are welcome.

Battery voltage should read around 13.6 engine off.
If not you have a problem there.

Codes do not say bad sensor.

What was the code no?

O2 sensors do not cause voltage drops.

If you have a voltage drop start at battery and clean and check all cable ends both positive and grounds from battery to engine and frame and to fuse box.
Then check wiring from fuse box on to ign switch and to all power feeds.

Was that the parts place code reader guy that gave you the advise?

cwby94
10-28-2011, 04:44 AM
hello MT. thank you for replying. i just stepped out and checked the battery voltage and got 12.51 . this is a napa legend 75 battery that i bought new last weekend. i don't know if the kind and age of the battery matters but there it is, well i kinda hope it does because it cost $113 haha. thank you for ruling out the o2 sensor. my buddy was pushing that theory pretty hard but nobody else thought so either.
I can't remember that actual code number right now but i have it written down at home (i work nights). the guy at oriellys said it was bank 1 sensor 2 heated oxygen.

the code reader guy at oriellys is the one that told me i had bad heated o2 sensor and i would have to by both rear one because the code doesnt specify which one of the 2 is bad.

a guy from my work is the one pushing the o2 sensor theory causing these problems.

for the wire going from the battery to the starter ... i disconnected it from the battery only. put test lead on the starter connection and the loose wire at the battery and got 10 ohms. is that normal to have that many ohms in a wire only with no other resistence source? that just seems kinda high for a straight shot through wire.

i know very little about vehicle mechanic so this is a big help .. thank you again

MT-2500
10-28-2011, 07:21 AM
hello MT. thank you for replying. i just stepped out and checked the battery voltage and got 12.51 . this is a napa legend 75 battery that i bought new last weekend. i don't know if the kind and age of the battery matters but there it is, well i kinda hope it does because it cost $113 haha. thank you for ruling out the o2 sensor. my buddy was pushing that theory pretty hard but nobody else thought so either.
I can't remember that actual code number right now but i have it written down at home (i work nights). the guy at oriellys said it was bank 1 sensor 2 heated oxygen.

the code reader guy at oriellys is the one that told me i had bad heated o2 sensor and i would have to by both rear one because the code doesnt specify which one of the 2 is bad.

a guy from my work is the one pushing the o2 sensor theory causing these problems.
for the wire going from the batt.ery to the starter ... i disconnected it from the battery only. put test lead on the starter connection and the loose wire at the battery and got 10 ohms. is that normal to have that many ohms in a wire only with no other resistence source? that just seems kinda high for a straight shot through wire.

i know very little about vehicle mechanic so this is a big help .. thank you again

A full charged battery should read 13.6 volts.
2.2 volts for each cell.
And check direct to battery post.
Not at cable ends.
Follow your pos. power on up to where it is losing voltage.
And also remember a bad ground can drop voltage to.



Codes do not say 02 sensor bad.
But should speel out witch on has a problem.
Post back that code no.

cwby94
10-28-2011, 08:02 AM
good morning MT. I just happen to have found the code in my work notebook also.

code: P0141
below the code it read: 02 heater circuit (bank 1, sensor 2)

after your first reply i went out and took the ground wires off the frame and body and cleaned them up good. the frame ground was tight but pretty dirty. kinda curious how the frame ground got so messed up under the connectors when it was screwed tight to the frame.

sorry i didnt mention this earlier but it just came to me tonight. not 100% sure but i think this all started after my buddy cleaned the engine with his pressure washer. he said he sprays his engine 2 times a year and no problems at all so i let him do it.

MT-2500
10-28-2011, 12:23 PM
good morning MT. I just happen to have found the code in my work notebook also.

code: P0141
below the code it read: 02 heater circuit (bank 1, sensor 2)

after your first reply i went out and took the ground wires off the frame and body and cleaned them up good. the frame ground was tight but pretty dirty. kinda curious how the frame ground got so messed up under the connectors when it was screwed tight to the frame.

sorry i didnt mention this earlier but it just came to me tonight. not 100% sure but i think this all started after my buddy cleaned the engine with his pressure washer. he said he sprays his engine 2 times a year and no problems at all so i let him do it.

Check it out and see if cleaning te grond fixed it.

Did the code and voltage problem start at or right after engine clean.

On codes always clear and see if they return.
Posable you voltage drop could be causing voltage problem to 02 sensor heater circuit.
Your code is for heater circuit problem.
Check votage to sensor and ground and wiring and sensor plugin.

j cAT
10-28-2011, 03:19 PM
i got this 96 suburban k1500 LT 2 months ago and now having electrical problem. the volt gauge fluctuates from approx 15 down to 10 and the lights dim almost off and the heater slows way down. i put in new alternator and battery and replaced stock wire from alt to battery + with a 4 ga wire. i cleaned and tightened battery connections and body ground from battery. i took out ALL dash switches to look for loose or bad connections and found none. i found an alpine security system way up inside of dash that i wasn't aware of and have no means of controlling it so i took out all in line fuses that went to the security units. checked wire from battery to starter and got 10 ohms. ...
after start up, length of time varies, the volt gauge will slowly go down until the fluctuations start and if turn on lights or heater then the drop is much faster.

volt meter across battery while running is 14.2 - 14.6.
across battery not running is 12.? ..
the belt isnt new but its tight and its not cracked or frayed

check engine light came on and code reader showed bad #2 heated oxygen sensor. most people tell me this would not be the cause of the electrical problem so i havent changed it yet. the guy that told me to take the fuses out of the alarm system says that the o2 sensor could cause the problem.

i would really appriciate any help with this . Thank you

this to me is a belt issue. the belt when old hard and possibly having oil on it will slip when the alternator starts cranking out high current. see if you can rotate the alternator with engine off with some resistance/force.

if you have an idlertension pulley this can be bad.

V groove belts are tricky. the Vee gets smaller then lacks grip.


a lead acid vehicle battery has 6 cells 2.1 volts per cell across the battery fully charged with engine off no load it should read 12.6 volts.....after the battery has been at rest for an hour....

this does not mean much however as the battery needs to be load tested to be sure the internal cells are good.

this can be done at most autopart stores that sell batteries. a quick test would be to put all lights on engine off and see if the voltage stays up at the 12.6 volt area.

j cAT
10-28-2011, 03:41 PM
hello MT. thank you for replying. i just stepped out and checked the battery voltage and got 12.51 . this is a napa legend 75 battery that i bought new last weekend. i don't know if the kind and age of the battery matters but there it is, well i kinda hope it does because it cost $113 haha. thank you for ruling out the o2 sensor. my buddy was pushing that theory pretty hard but nobody else thought so either.
I can't remember that actual code number right now but i have it written down at home (i work nights). the guy at oriellys said it was bank 1 sensor 2 heated oxygen.

the code reader guy at oriellys is the one that told me i had bad heated o2 sensor and i would have to by both rear one because the code doesnt specify which one of the 2 is bad.

a guy from my work is the one pushing the o2 sensor theory causing these problems.

for the wire going from the battery to the starter ... i disconnected it from the battery only. put test lead on the starter connection and the loose wire at the battery and got 10 ohms. is that normal to have that many ohms in a wire only with no other resistence source? that just seems kinda high for a straight shot through wire.

i know very little about vehicle mechanic so this is a big help .. thank you again

the code p0141 is the driverside after converter O2 sensor. this with just the 141 code means the O2 sensor is defective or the connector/wires have an open heater circuit.

again this is because you have only this 141 code.

I would check this O2 issue out. though the after converter O2 sensors are only a reporting issue on how well the converters are operating.

In my area you would fail the emission test.

j cAT
10-28-2011, 03:46 PM
checked wire from battery to starter and got 10 ohms. ...


i would really appriciate any help with this . Thank you

the wire from battery to starter the big one should read zero OHMS...

remove the wires to the starter and clean them . also recheck the wire resistance and any corrosion on the connectors ends or wires that are eaten by acid.

cwby94
10-28-2011, 05:26 PM
thank you everyone. i just woke up so after i get a coffee im going out to get started on things suggested.

MT - cleaning those grounds made a noticable difference. the volt gauge is much more stable.. doesnt drop like before but still has the problem. now instead of the volt gauge slowly dropping it stays over 14.

the recent events:
pressure wash engine
change first alt (bought remanufactured from oriellys)
oriellys for battery test. he said alt was bad. so he sold me a new (not remanufactured) alt
--- his battery test meter said alt had something about a ripple effect going on.
napa for second opinion on battery test. they said battery was weak. bought new battery
and put in the new battery and the new new alternator.

the o2 was before the battery and alternator mess. i just cant remember if it was before or after pressure washing engine.

coffee time. i will be back later with result of the suggestion.

thanks guys

cwby94
10-29-2011, 06:48 PM
;lkj

cwby94
10-29-2011, 07:05 PM
sorry. this is the 3rd time i wrote all this out and it didnt post.

pulled o2 sensor out and tip was kinda grey and not gritty. around the base of the sensor was black soot. the connection was tight and inside the connectors was very clean. chilton book said test between A and B but i didnt see any markings on the sensor or connectors. there is 4 pins in the plug and i had contituity between 2 of them and not the other 2.

the o2 code was deleted after i wrote down the code and the check engine light went off and has not came on since.

i put a cresent wrench on the alternator pulley nut and yes.. i was able to turn the alt and the belt didnt move. the belt has 6 grooves.

j cAT
10-29-2011, 08:09 PM
sorry. this is the 3rd time i wrote all this out and it didnt post.

pulled o2 sensor out and tip was kinda grey and not gritty. around the base of the sensor was black soot. the connection was tight and inside the connectors was very clean. chilton book said test between A and B but i didnt see any markings on the sensor or connectors. there is 4 pins in the plug and i had contituity between 2 of them and not the other 2.

the o2 code was deleted after i wrote down the code and the check engine light went off and has not came on since.

i put a cresent wrench on the alternator pulley nut and yes.. i was able to turn the alt and the belt didnt move. the belt has 6 grooves.


take the belt off and check the tensioner . this may be broken or rusted up and not appling proper tension.

belts can be tricky on purchasing the correct width and length.

small cracks on the inner groved area would mean new belt .

cwby94
11-01-2011, 06:38 PM
today i replaced the o2 sensor , belt and belt tensioner. problem still there. the heater is working intermittently to.

j cAT
11-02-2011, 07:41 AM
today i replaced the o2 sensor , belt and belt tensioner. problem still there. the heater is working intermittently to.

post #9 I stated checking the wire to starter and the connections wire condition. also look at the fuseable links . if green corroded these will need replacing.

since this is an old vehicle it is possible and some , have had issues with the fuse sockets being loose. this can happen when fuse removal stresses out the socket with flexing the fuse on trying to remove.

cwby94
11-02-2011, 09:19 AM
sorry. after i read that i bought a new wire it run from the battery to the starter but got busy with work and it slipped by me. i will be putting the new wire on today after i get some sleep and i will post back what i found with the old wire.

the only fuseable link im aware of is from the alternator to the battery. on a friends suggestion i took the wire and link out and replaced it with a 4 ga wire. the wire i bought to go to the starter is a 4 ga wire also.

cwby94
11-03-2011, 11:08 PM
i got to the block ground tonight and cleaned it. there was a lot of dirt on top but when i got the connections off they didn't look to bad. the block itself and the connectors where pretty clean.

i replaced the wire from battery to starter. the old wire ohm at .3 . after all that i think i know how we came up with 10 ohms on the wire. my buddies know a lot more about this stuff than i do but this makes me very happy i found this site and really appreciate your help.

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