Oil Pressure and Battery Gauge Fluctuation- is it normal?

thilton19 · February 18, 2014

Hello All,

I have a 2010 Sierra 1500 SLE with about 70k+ miles on it. Over the past month or so I've noticed that my oil pressure gauge and my battery gauge has been fluctuating readings. I'm more concerned about the oil pressure. When I first bought is last November the oil pressure would read above 40. Now, it fluctuates between 20 and 40 during normal operation. When I first start it the oil pressure reads around 40. As for the battery gauge, sometimes it'll read over 14v and sometimes around 12v. Also, these reading can fluctuate between drives. For example, when I first start the truck I get oil pressure at 40 and battery at 16v. If I run a few errands, turning the truck off at each stop, it may show oil pressure at 20 and voltage at 12v.

As this is my first GMC truck I'm wondering is this normal? I've checked the oil and the dipstick shows full. As for battery charge, the truck starts everytime without lag.

Please share your experiences and advise. I look forward to the insight. Perhaps there's a simple explanation for this, like my gauges are failing or I just need to change my oil.

Let's discuss.

Thanks!

Troy

cobrajet84 · February 18, 2014

I'm not positive on the oil gauge, but I do know that the battery gauge will fluctuate as the computer adjusts output to the trucks needs. I haven't noticed the oil gauge drop before but I have seen it increase in cases of hard acceleration, etc. I may have to play closer attention now.

2017SierraSLT · February 18, 2014

The voltage will fluctuate a lot with the stock system. One way to stop it is to disconnect the battery load sensor on the negative battery cable. Then your voltage will be consistently at or slightly above 14. The oil pressure on the LS engines is normally 40-45 hot at cruise speeds. It should never dip below 20-25 at slow idle, hot in drive.

MaverickZ71 · February 19, 2014

I used to drive Ford trucks and their oil, volt, and temp gage needles never moved after startup, so that really faked me out when I got my '09 Silverado. What you are describing is totally normal for the GMT900 trucks. The PCM apparently adjusts the alternator output (to save gas mileage?) and even the oil pressure(!) according to rpms, temperature, etc. The owner's manual indicates that needles pointing "straight up" on the temp, oil pressure, and voltage gages is is where the normal average should be (like it is set up on semi trucks), and anything within the range of one hash mark above and below the midline is within the normal acceptable operating range.

MikeInCtown · February 19, 2014

Wow, my oil pressure never drops below 40, and while driving is normally at 50-60. alternator is always around the 14v mark, or just slightly past my midpoint on the gauge. I have an 04 though. It would worry me if the voltage ever got around 12v as it is always supposed to be almost 13 at the very least as a fully charged battery is 12.8 or above. most accessories are meant to run at 14.x volts.

MaverickZ71 · February 19, 2014

Wow, my oil pressure never drops below 40, and while driving is normally at 50-60. alternator is always around the 14v mark, or just slightly past my midpoint on the gauge. I have an 04 though. It would worry me if the voltage ever got around 12v as it is always supposed to be almost 13 at the very least as a fully charged battery is 12.8 or above. most accessories are meant to run at 14.x volts.

I like the way yours (GMT800) works better than the way the next generation (GMT900) works. So many things constantly altered by the PCM, mostly to gain a little gas mileage or for emissions control. Suppose it's only gonna get worse in the coming years on the new aluminum pickups.

GMCustomerService · February 19, 2014

thilton19,

Hello! I understand that you are seeking advice from your awesome fellow forum members and I might not be able to give you any technical advice but I would be happy to assist. If you find that your vehicle needs to be diagnosed at a dealership I would be happy to locate a dealership in your area and set up the appointment. Please private message me if I may be of any assistance.

Jennifer T.

GM Customer Care

thilton19 · February 20, 2014

thilton19,

Hello! I understand that you are seeking advice from your awesome fellow forum members and I might not be able to give you any technical advice but I would be happy to assist. If you find that your vehicle needs to be diagnosed at a dealership I would be happy to locate a dealership in your area and set up the appointment. Please private message me if I may be of any assistance.

Jennifer T.

GM Customer Care

Thanks Jennifer T., but i have a dealership just around the corner from me. I can schedule an appointment if needed.

GMCustomerService · February 21, 2014

thilton19,

You are welcome. I understand that there is a dealership near you. Please keep us updated on your vehicle concern.

Jennifer T.

GM Customer Care

ATMINF · February 22, 2014

Rick, can you attach a pic of the sensor to disconnect? Or give a good description of it, I would like to disconnect the sensor in my truck. Thanks

2017SierraSLT · February 22, 2014

Rick, can you attach a pic of the sensor to disconnect? Or give a good description of it, I would like to disconnect the sensor in my truck. Thanks

From another board member's truck. Note the plug in the supplied photos that is wrapped in electrical tape. This is the current sensor.

mike94silverado · February 23, 2014

I just got an edge insight monitor... It reads the same info and fluctuates the same..... I guess GM gauges are real gauges and not "fake" like other trucks I've driven.

thilton19 · February 23, 2014

Thanks all. I'm actually feeling a bit better about my truck. Since I bought it used, and I did my homework on it, i still always wondered if perhaps I'd have issues later on (did I buy someone else's problems), so when I saw the fluctuations in the gauges I got worried. So far, gauge operation has been consistent and the truck is running just fine. When I take it in for service next month I'll have everything checked over just to be sure.

Peace!

Troy

azmusclecar · April 7, 2014

I just went through this issue with the battery gauge yesterday. I went on a trip from Tucson to Phoenix and about half way there I saw the voltage drop under 14 volts. I started to turn things off, DRLs and A/C and anything drawing current. My eyes were focused like a hawk on that gauge and in a bit, it went up over 14 to maybe 14.5 and stayed there for a period of time. I picked my wife up at the airport and the gauge read 14 most all the time. Same thing happens on the way home. Gauge drops to 12.5 for a period and then back to 14. Now I know the DIC AVG MILEAGE is not exact but my mileage showed 22.1 for the trip. That's a 5.3, 3.08 gear, 6 speed, avg 65-70 mph with a tonneau cover.

So if this engineering saves gas by cutting voltage I guess I'll live with it but it sure makes us old schoolers sweat bullets. Especially when 30 pounds of oil pressure at idle is okay when I'm used to old school 40. Technology is dragging me kicking and screaming like a child but I'm going there maybe unwittingly, but not so much willfully.

My truck is a 2010 LTZ. Nicest truck I've ever owned.