2011 5.3 and the infamous P0521 code

gealzonwheelz · March 30, 2017

I spoke with the service director just now, he called after seeing a negative review under their service satisfaction survey they sent me

because of the P0521 code, they are still pointing fingers at replacing the sensor, which was done once and did not fix the issue, and he still did not want to believe that changing the oil and filter was allowing the CEL to be cleared

so, I'm gonna run it for now, if the CEL returns, I will change the sensor one more time, if the CEL does not clear, I will change only the filter and continue to diagnose without the help of the dealer

Coby7 · March 30, 2017

Way to go, that's hitting them where it hurts.

Dixon700 · January 14, 2018

As of yesterday my '13 with 49k miles has this issue, it's also started using a lot of oil. It used to use about a qt in 5k miles. Now it's used almost a gallon in 3,200 miles. I'm original owner. So should my power train warranty cover any issue my engine is having right now? My oil psi has never dropped below 25psi.

Dixon700 · January 14, 2018

Warranty ran out this month... This month was 5 years, so I guess start with a new sender?

carnau · January 15, 2018

9 hours ago, Dixon700 said:

Warranty ran out this month... This month was 5 years, so I guess start with a new sender?

I am actually making a video on the repair for this. The passage really needs to be cleaned out. The trash falls back down into the oil filter and as soon as you crank it up after replacing the oil pressure sensor and the filter the clogs up the new oil pressure sensor filter and you are back with the same code. The oil pressure sensor passage goes right to the oil filter. Remove the oil pressure sensor, filter and the Engine oil filter and blow all that trash out the bottom.

I have never had one return after doing this. I will post the video when I am done with it. Will be in the next day or 2.

carnau · January 15, 2018

Here you go.

Dixon700 · January 15, 2018

Good video, I'm just not sure how much junk mine will have in there since it only has 49k mi. I'm ordering new sender and oil filters, so I'll change filter and blow it out when I'm replacing the sender.

Dixon700 · February 1, 2018

Replaced the sender and both filters after. Losing it all out and so far so good.

The dealer wanted $370 to replace the sender and filter... All of it was like 40min... ???.

swathdiver · February 1, 2018

P0521 does not necessarily mean the problem is always the sensor. It can also indicate wiring or the ECM going/gone bad. Further testing should be done according to the manual.

carnau · February 1, 2018

11 hours ago, swathdiver said:

P0521 does not necessarily mean the problem is always the sensor. It can also indicate wiring or the ECM going/gone bad. Further testing should be done according to the manual.

Always! Always! Always! Always check test the vehicle before replacing anything! Very good advice!

Dixon700 · February 5, 2018

On 2/1/2018 at 6:59 AM, swathdiver said:

P0521 does not necessarily mean the problem is always the sensor. It can also indicate wiring or the ECM going/gone bad. Further testing should be done according to the manual.

I had the dealer diagnose it. I paid them $85 for that so they better of properly diagnosed it. I don't have access to gm manuals or all data program, or anything like that to get diagrams and pinout to test the harness or sensor. I could of ohmed the sensor out, but i don't know which pins or the range it should fall in and what resistance should be at the different pressures.

swathdiver · February 5, 2018

Well, anyone can buy a subscription at ALLDataDIY for their truck and have access to just about all the information they need to keep their rig in top form. A Tech2 or advanced scan too is a must as well; they pay for themselves very quickly in precious time and money saved too.

Dixon700 · February 8, 2018

I have auto enginutity, but I don't have the enhanced gm package, I have the enhanced package for my dodge. I never wasted the extra money on having the gm enhanced also because I only had my 02 before and it runs ok with 220k mi. Heck a subscription to all data would probably cost more than $85 I paid to Johnson motors to diagnose my p0521.

Brad1984 · February 9, 2019

I know I'm a little late to the game here but I just had this problem and thought I'd share....

I have a 2013 GMC Sierra 1500 SLE 5.3L. Bought it as second owner with (at the time 31,000 miles). Have all the service records from the previous owner.

It now has about 64,000 miles. Recently (at 63,200 miles) I had the normal oil and filter change. I usually use any good full synthetic and a K&N oil filter. I decided to change it up and tried out Mobil1 Annual Protection and a Mobil1 Annual protection oil filter to see how it does. Now before I get yelled at I would never go 20,000 between oil changes like Mobil1 claims can be done with the setup. I only do 7,000 or 8,000 miles a year in this truck.

Anyways, immediately after this oil change I noticed and change in my oil pressure. I was use to seeing a minimum of about 27 psi at idle and 40 psi plus at highway speeds with the oil fully hot. After this oil change I was getting 18-20 psi at idle and maybe 25 psi at highway speeds under the same conditions.

I watched the gauge over the past 800 miles and it stayed about the same. I thought "well, good rule of thumb is 10 psi per 1,000 RPM."

Today I got a engine check light and it was a low pressure warning. Took it to my mechanic and he crawled through it and tested the sensor and said it seemed to be working properly but to maybe replace it. He also said it could be a bad oil pump or clogged oil filter but that would be unlikely due to be a good filter and good oil. I asked him to change the oil filter and oil and we'll go from there. I bought Valvoline full synthetic and a Purolator BOSS oil filter and had him do the change....

There was a immediate change! Drove the truck on back roads and the highway for 30 miles. Speeds from 5 mph to 75 mph. Also with it in tow mode some of the way to get higher rpms. Everything is back to the way it use to be. There was no viable sludge in the oil filter or lower engine (he used a little snake camera through the drain hole to show me). He thinks the oil filter was either incredibly clogged with God knows what or the filter media was poorly made and caused the oil to bypass the media through the valve...

Either way I'm happy so far. Hope this may help someone!

carnau · February 10, 2019

On 2/9/2019 at 6:03 PM, Brad1984 said:

I know I'm a little late to the game here but I just had this problem and thought I'd share....

I have a 2013 GMC Sierra 1500 SLE 5.3L. Bought it as second owner with (at the time 31,000 miles). Have all the service records from the previous owner.

It now has about 64,000 miles. Recently (at 63,200 miles) I had the normal oil and filter change. I usually use any good full synthetic and a K&N oil filter. I decided to change it up and tried out Mobil1 Annual Protection and a Mobil1 Annual protection oil filter to see how it does. Now before I get yelled at I would never go 20,000 between oil changes like Mobil1 claims can be done with the setup. I only do 7,000 or 8,000 miles a year in this truck.

Anyways, immediately after this oil change I noticed and change in my oil pressure. I was use to seeing a minimum of about 27 psi at idle and 40 psi plus at highway speeds with the oil fully hot. After this oil change I was getting 18-20 psi at idle and maybe 25 psi at highway speeds under the same conditions.

I watched the gauge over the past 800 miles and it stayed about the same. I thought "well, good rule of thumb is 10 psi per 1,000 RPM."

Today I got a engine check light and it was a low pressure warning. Took it to my mechanic and he crawled through it and tested the sensor and said it seemed to be working properly but to maybe replace it. He also said it could be a bad oil pump or clogged oil filter but that would be unlikely due to be a good filter and good oil. I asked him to change the oil filter and oil and we'll go from there. I bought Valvoline full synthetic and a Purolator BOSS oil filter and had him do the change....

There was a immediate change! Drove the truck on back roads and the highway for 30 miles. Speeds from 5 mph to 75 mph. Also with it in tow mode some of the way to get higher rpms. Everything is back to the way it use to be. There was no viable sludge in the oil filter or lower engine (he used a little snake camera through the drain hole to show me). He thinks the oil filter was either incredibly clogged with God knows what or the filter media was poorly made and caused the oil to bypass the media through the valve...

Either way I'm happy so far. Hope this may help someone!

I have absoluelty seen bad filters cause this problem too. I had a customer come in the other day and he had just had an oil change done on his vehicles withing 200 miles. He had less than 12psi of oil pressure on the sensor. Tested the pressure at the oil filter using the oil pressure adapter. ( https://amzn.to/2DtzN6B ) and it had 22 at idle. Put his filter back on it and it went to 12 again. Changed his filter to an ACDelco filter and it went to 22 at idle on the dash. That was a Purolator filter as well. Not saying they are bad filters.