At idle, oil pressure drops and check gauges light turn on?

AJCHWICK

MEMBER
2002 CHEVROLET TRAILBLAZER
4.2L
6 CYL
4WD
AUTOMATIC
180,000 MILES

Vehicle listed above is an LTZ model.

While driving at any speed, all is AOK. But sometime, when idling, like at a light or stop sign, the oil PSI drops, and the Check Gauges (CG) light comes on. If I put the truck into neutral and rev up, PSI comes back up and CG light goes out, but if I don't, the computer display will change to Stop Engine. Sometimes, there is also an RPM drop with the PSI drop, but not all the time.

The Oil Pressure Sensor has been replaced twice, with the thought that the first one was just faulty.

The oil level is spot on, and the oil filter is new.
All fluid levels are also proper.

Is this a PCM issue?

Side issue: Items in the Lift Gate, ie Window defogger, rear wiper, and rear window washer do not function. BCM issue? Or possibly wiring at the lift gate hinge area?
Thank you.
Alan

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,192 POSTS

Alan,

If the oil pressure sensor has been replaced without change, there is a chance the oil pressure is low due to wear, sludge restricting oil pick up by the pump, and so on.

What you need to do is this. We need to check oil pressure using a mechanical gauge. Most parts stores will lend one to you. All you do is remove the electric sensor that is new and screw in the mechanical gauge. Start the engine and see what pressure the gauge says.

I looked up the manufacturer's specs for oil pressure. At 1200 RPMs, the minimum oil pressure should be 12 psi. I wouldn't expect it to go below 10 psi at idle.

Let me know if this helps or if you have other questions.

Take care,

Joe

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Tuesday, August 9th, 2022 AT 12:59 PM

AJCHWICK

MEMBER
3 POSTS

Thanks, I will investigate this, plus I may check out the Oil Pickup Screen to see if it is plugged with sludge.

On a side issue: Items in my Lift Gate, ie Window defogger, rear wiper, and rear window washer, do not function.
BCM issue? Or possibly wiring at the lift gate hinge area (where it crosses over in the hinge rubber boot)?
Any ideas would help.

Thanks.

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Tuesday, August 9th, 2022 AT 2:03 PM

JACOBANDNICKOLAS

MECHANIC
108,192 POSTS

Hi,

I would be happy to help with the liftgate issues, but I have a favor to ask. Could you copy and paste the new questions to a new thread? We try to keep the posts specific to one topic, so they are more helpful to others. I hope you understand.

Copy and paste your new question at this link (make sure you are logged into the site first):

https://www.2carpros.com/questions/new

Again, I hope you understand.

Take care,

Joe

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Tuesday, August 9th, 2022 AT 7:44 PM