High Oil Pressure, 2010 Yukon Denali

[Tim907356]

I've seen a few threads on this topic, but just want to justify my conclusions. I bought this Yuk a couple of weeks ago, and it threw a P0521 code on a 100mi. trip today. I had it read (left my OBD2 at home!), at an Autozone, and then noticed that the gauge was indeed reading a good bit higher than when I bought it. Now, it runs at normal loads of 1500-2000rpm's, at about 65psi.
After reading some threads, I went out and checked that the gauge reads ~30psi with the engine off. No way there should be running pressure with nothing pumping, right? Doing the math, the real pressure is ~65-30=35psi, right about what it should be while running.
So, I say it's the sender....does that sound like the logical conclusion?...just wanted to check before I get greasy.

 

[Fless]

A good code reader (Tech 2?) will show what the sender is returning for voltage, which would be an indicator if it's high. I'm not sure what normal voltages are for NNBS but I have documented several of mine for my NBS in another post.

 

[swathdiver]

I bought this Yuk a couple of weeks ago, and it threw a P0521 code

That's a code that the sensor itself should be bad.

Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) sensor.
2. Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal 1 and ground.
 If greater than the specified range, test the low reference circuit for an open/high resistance. If the
circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
 If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high
resistance. If the circuit tests normal, replace the ECM.
 If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the
circuit tests normal, replace the ECM.
4. Verify the scan tool Engine Oil Pressure Sensor parameter is less than 8 kPa (1.2 psi).
 If greater than the specified range, test the signal circuit terminal 3 for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the ECM.
5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit
terminal 2. Verify the scan tool Engine Oil Pressure Sensor parameter is greater than 550 kPa (80 psi).
 If less than the specified range, test the signal circuit for a short to ground or an open/high
resistance. If the circuit tests normal, replace the ECM.
6. If all circuits test normal, test or replace the EOP sensor.

 

[Tim907356]

I don't have a tech II. If I get close enough to the sensor to take electrical readings, I'll probably just pull the sucker and put a new one in: Holy-wow that thing is buried back there! For ~$30 or so for a new one on line, that's probably the track I'll take. I just want to know if its the likely culprit.

Nice sign off swathdiver, by the way (Mk.1:15)

 

[OR VietVet]

My 2002 will have normal oil pressure after start and thru all the load and warming cycles. When I shut it off the oil pressure reads near 30 psi sitting there. If I cycle the key to KOEO and back it drops. I just recently noticed this and reads great oil pressure driving warm at 45-50 psi. No engine noises. I know different year and everything but I am not gonna worry about that reading when shut off.

 

[swathdiver]

I don't have a tech II. If I get close enough to the sensor to take electrical readings, I'll probably just pull the sucker and put a new one in: Holy-wow that thing is buried back there! For ~$30 or so for a new one on line, that's probably the track I'll take. I just want to know if its the likely culprit.

Nice sign off swathdiver, by the way (Mk.1:15)

Thanks, you can use a multimeter for some of that work. It's either a wiring problem, a bad sensor or the computer. I'll trust the computer's self diagnostics and say it's the sensor.

Get a Tech-2!

 

[Tim907356]

What's a good one....they ain't cheap!

 

[OR VietVet]

You want a good one for money, get a Fluke. But they can be had for very little money. Digital or analog. I used to have a FLUKE years ago but I bought one at NAPA 5-6 years ago for $40 and it works fine. The more you pay the more it does.

 

[thompsoj22]

I've seen a few threads on this topic, but just want to justify my conclusions. I bought this Yuk a couple of weeks ago, and it threw a P0521 code on a 100mi. trip today. I had it read (left my OBD2 at home!), at an Autozone, and then noticed that the gauge was indeed reading a good bit higher than when I bought it. Now, it runs at normal loads of 1500-2000rpm's, at about 65psi.
After reading some threads, I went out and checked that the gauge reads ~30psi with the engine off. No way there should be running pressure with nothing pumping, right? Doing the math, the real pressure is ~65-30=35psi, right about what it should be while running.
So, I say it's the sender....does that sound like the logical conclusion?...just wanted to check before I get greasy.[/Q

That's a code that the sensor itself should be bad.

Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) sensor.
2. Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal 1 and ground.
 If greater than the specified range, test the low reference circuit for an open/high resistance. If the
circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
 If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high
resistance. If the circuit tests normal, replace the ECM.
 If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the
circuit tests normal, replace the ECM.
4. Verify the scan tool Engine Oil Pressure Sensor parameter is less than 8 kPa (1.2 psi).
 If greater than the specified range, test the signal circuit terminal 3 for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the ECM.
5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit
terminal 2. Verify the scan tool Engine Oil Pressure Sensor parameter is greater than 550 kPa (80 psi).
 If less than the specified range, test the signal circuit for a short to ground or an open/high
resistance. If the circuit tests normal, replace the ECM.
6. If all circuits test normal, test or replace the EOP sensor.[/QUOTE

Dont the stepper motors normally return to zero after power off? Your TS tree is spot on, im just wondering why the needle stays at 30 psi? Will the TECH2 run the cluster?

 

[swathdiver]

Dont the stepper motors normally return to zero after power off? Your TS tree is spot on, im just wondering why the needle stays at 30 psi? Will the TECH2 run the cluster?

I noticed this too but thought it would be better to solve for the trouble code first. Yes, the Tech-2 can test the cluster and sweep the gauges to test them. As for returning to zero, I thought so too but never really paid attention. Ron says his does.

Tim, Tech-2s are about $350 delivered on Ebay. If you have a tablet, you can get the VXDIAG NANO and run Tech-2-Win on it and it also comes with GDS2 software.

A bi-directional scan tool is the most important tool a man can have for working on these trucks.