4.0L - Changing Crank Positions Sensors

[genedjr]

On the 2nd Gen 4.0 the crank position sensors are fairly easy to change.  Yesterday I replaced both with a pair of junk yard ones.  I saw one video where the guy removed the oil filter and adapter, but this is not necessary on the Aurora.

Here is what I used:

• Jack to put car on jack stands - I have a floor jack
  
• Jack stands that get the car high enough you can roll over while under the car.
  
• 1/4" socket wrench, 15" of extension, universal joint, and a 10mm socket.
• 16" long thin straight blade screwdriver.
• Light source.
• Telescoping magnet to pull and push the sensor bolts.
• Regular flat screwdriver to help with plastic push pins.
• Also shown are the original and new sensors.
  

 
 

Here is how to do it:

• Place the car on jack stands.  I placed the stands under the back engine cradle mount bolts.  Make very sure its stable.  I had mine up 15" and at 6'4" and 210lbs I had plenty of room using a creeper.
  
  
  
• Remove the splash under cover (or whatever it's called).  Be careful with the plastic push pins as they break very easily.  You can get new ones from the local parts store or just pull a few when at the junk yard.  You'll need at least 4 good ones to secure the cover.  But more are recommended.  Also be careful where you set this cover as it will bend and crack fairly easily.
  
  
  
• The Crank Position Sensors are almost directly behind the front motor mount and exhaust manifold.  If that area is a oily mess, with the front cover off, go out to the car wash and hose it down.  You really don't want greasy dirt to fall into the engine.  If you do need to run out and hose it off, you are done for the day as it gets extremely hot behind the front exhaust manifold.
  
  
  
• Using a light to see, each sensor has a connector that needs to be removed.  These are the only connectors directly behind the front motor mount.  On the bottom sensor the release is on the bottom, you need to pinch the tab and pull the connector.  The release was pretty stiff and this was hard to push.  The top sensor has the tab on the top.  Pinch and pull.
  
  
  
• To make it easier I pushed these wires out of the way.  Make note of the color of each connector, where it goes, and write it down.  I am not sure if they can be reconnected backwards, but that would be bad.
• Also note that the top sensor is grey and the bottom sensor is black.  The sensors appear to be mirror images of each other.  Again putting them in wrong hole would be bad.
  
  
  
• I used 1/4" ratchet, 15" or so of extension, a universal joint, and a 10mm socket.  Even with my size 3x hands I was able to guide the socket to the bolt loosen and remove.  The path was over the cross member that has the brake lines running across it. I took both bolts out first as it's a bit hard to get my hand up in there. (If you have smaller hands you can probably just use the ratchet and socket - there is alot of room up there.)
  
  
  
• Now using a 16" thin flat blade screwdriver I was able to gently pry (by twisting the screwdriver) the sensor out twisting at the mounting tab of the sensor and the engine.  If you have smaller hands you can probably just twist the sensors out.  They use O-rings for the seal and that is all that is holding them in.
  
  
  
• Sensors out
  
  

Reassembly is just reversing the above.  Remember the O-ring is the seal so you only need to snug the bolts tight.  Remember the color of the connectors, even time helps here as my connectors just lined up correctly.

One side note:  The sensor should be a little hard to push in.  My top was way to easy and I noted that it had the wrong o-ring (smaller).  I put another on and it fit tightly like the bottom (sorry the pictures to not show the 1/2mm difference but its obvious to the naked eye.

On a scale from 1 (easy peasy) to 10 (need a pro and full shop) this is a 2 if you have the tools listed above.

Enjoy.

...gene

EDIT: Added Pictures.  This third time counting the junk yard removal took about 30 minutes including taking pictures.  Enjoy.

[Paulaurora]

nice!

[plato442]

Gene, nice write up. But the big question... Did it solve your misfire!!??

[genedjr]

Apparently not.  Got the same code last night.
...gene

[guy48065]

Bummer. But thanks for the excellent how-to. It's nice to know I don't really have to drain the oil and remove the filter just to reach that sensor.

[Marc]

Oct 31, 2014 8:39:47 GMT -6 genedjr said:

Apparently not.  Got the same code last night.
...gene

It may be that the sensors that you got at the yard are bad. And you might have to do the CKPS relearn procedure. You need a Tech 2 for that.
See that below.

[guy48065]

Do I remember right that if you don't do the Tech2 re-learn it will eventually sort itself out in a few re-starts?

[awehlage]

Oct 31, 2014 20:41:11 GMT -6 guy48065 said:

Do I remember right that if you don't do the Tech2 re-learn it will eventually sort itself out in a few re-starts?

Yes!

[TheBac]

Man, talk about nice timing. I need to change out the crank sensors on my 03 tomorrow. Thanks!
She began stalling right after a cold start and RPM dropping off when letting off the gas last week and the code pointed to the crank sensor.

[plato442]

Gene, yeah I'd definitely replace those parts with new OEM to try and verify the problem, not used from a yard. Something as sensitive and those sensors I'd definitely want a new oem. I'll be ordering mine soon

[TheBac]

New sensors fixed the issues with my car. Glad I caught it when I did.

[genedjr]

Thanks for all the advice and yes, I am ordering new ones.  And yes, it appears to have sorted itself out even with the old ones.

I am glad to hear that it will eventually sort itself out as this car will never see a dealer again.

...gene

EDIT: Ordered, Amazon Prime, ~$80 for both.

[genedjr]

OK, replaced the sensors with the new ones.  When I got the ones out of the junk yard, it took over an hour to get them out of a caddy that had the radiator and condenser already out.  The first replacements with the junk yard ones on the Aurora took probably hour and a half.  This time 30 minutes at most.

After replacement I cleared the P0300 code (random misfire) and will continue clearing codes for a couple of weeks.  If it finally stays cleared I will let everyone know.
...gene

[genedjr]

Well, after 3 days and a dozen starts or so, I was still getting misfire code.  Today, I decided to play around with it and for 20 minutes, it would consistently throw P0303 (cyl 3 misfire).  I am going to continue to let it sort itself out for a few more days.  If the single code remains, I will open a thread for documenting the fix.

But replacing the crank position sensors was a good thing.
...gene

[genedjr]

The P0303 was a fluke.  The very next day it throws the P0300 random misfire and has continued almost every time the car is used.  It's now been a couple of weeks and it is still throwing the code.  I assume the the PCM would have "learned" the values by now.  It does run better, so this was a good fix.  But alas, not a complete fix.
...gene

[btwnjondcy9902]

Great post genedjr. Very helpfull. Just finished replacing both sensors on my 2G-2002. Had codes P0385 and P0386 set and car stalled once while slow driving. Pretty small access. I was able to pinch connectors to release them but not able to pull it with my hand. I guess my hand is too big. I had to start from lower sensor by pinching connector with my right and with left hand prying out connector using flat screwdriver from bottom access next to oil filter. Then I removed a screw and I pulled lower sensor. The second upper sensor I did the same way. I needed 2 hours for whole thing.       

[julieaurora]

they said my 6 cyclinder states i only need one is this for 8 cyclinder

[plato442]

this is for the 4.0

[ejohnson03]

Would it not be easier to remove the Coolant overflow tank to access the Crank Sensor?

[sall]

Do you mean the radiator...? Unless you have a 3.5L... I don't know where they are located on it.

[tigger]

Apr 1, 2015 9:05:11 GMT -6 ejohnson03 said:

Would it not be easier to remove the Coolant overflow tank to access the Crank Sensor?

Removing the tank does make it easier to access the camshaft position sensor(CPS) on the 2G, the crankshaft position sensors (CKPS) are located on the radiator side of the engine.

[gordy]

Where is the crank sensor located on 1996 aurora?. I been looking and I dont seem to find it. I have a 4.0 V8. Thanks

[sall]

Apr 3, 2015 19:50:09 GMT -6 gordy said:

Where is the crack sensor located on 1996 aurora?. I been looking and I dont seem to find it. I have a 4.0 V8. Thanks

*crank*. Two different drugs, but the sensor won't help locate either. Anyways, they(there are two) are above and to the right of the oil filter adapter. Same location as the 2G shown here.

[gordy]

Thanks

[plato442]

its fairly tight tho!

[presumido]

I recently changed both a and b crankshaft sensors on my 2001 oldsmobile aurora 4.0 and now the car is hard starting. I was informed to do a relearn to get both sensors back in sync so i did that today and the result is still the same, hard start and the check engine light came back on. Sensor b which is the upper i bought from am autoparts online and sensor a the bottom sensor i purchased from autozone. The code refers to sensor b. A week prior to replacing the crankshaft sensors i replaced my starter and the car was starting perfectly until i changed the crank sensors. Anyone have a solution or suggestion since i followed all of the procedures to no avail?

[sall]

Mar 21, 2017 10:29:36 GMT -6 presumido said:

I recently changed both a and b crankshaft sensors on my 2001 oldsmobile aurora 4.0 and now the car is hard starting. I was informed to do a relearn to get both sensors back in sync so i did that today and the result is still the same, hard start and the check engine light came back on. Sensor b which is the upper i bought from am autoparts online and sensor a the bottom sensor i purchased from autozone. The code refers to sensor b. A week prior to replacing the crankshaft sensors i replaced my starter and the car was starting perfectly until i changed the crank sensors. Anyone have a solution or suggestion since i followed all of the procedures to no avail?

What is the code? To be honest though if they are not ACDelco parts, that is probably the problem. Why did you replace them if there was not a problem? Still have the old ones?

[Paulaurora]

Make sure they both same and not generic. Better ac delco. Did you le learn with tech 2?

[RCA1186]

Added to 2G mech maintenance stickies

[presumido]

I bought them from AM auto online so i believe they were generic. Also when they sent them they mistakenly sent 2 uppers so i had to get the lower sensor from autozone which is a duralast. The code is a P0386 Crankshaft B performance,P0386 cranksahft B performance, and P0385 sensor b circuit malfunction. And yes i had the relearn done at the autoshop. So if anyone has experience or prior issues with these codes could you please give me a suggestion? Finally, after seeing these codes do you believe its because my sensors are generic? And sensor B is the upper correct? And since there is no issur read by sensor a does that mean the lower sensor is okay?