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DelaneyElise

Delane ... 3/6/2019

2008 Buick Lucerne CXL 6 Cyl 3.80L

Engine

2008 Buick Lucerne new programmed PCM wont reprogram my key!

I have a 2008 Buick Lucerne CXL and I just replaced the PCM. My car stalled while driving on a busy highway 5 minutes after starting the vehicle. The car wouldn't restart and so I had it towed home. It threw a P0520 code. I changed both the Oil Pressure Sensor and the Crankshaft Position Sensor and nothing happened. The car would turn over, but not start. I was told by several people that the PCM needed to be replaced so I bought a used PCM from ebay and the seller took my VIN and programmed the PCM for my vehicle. I installed it on my car today and now I cant get my key to program to the new PCM even after following the directions they sent to me to follow. When the key is turned to the ON position, the check engine light comes on and stays on while the key is in. The security light comes on and then turns back off a few seconds later. The directions mentioned that this light should stay on the whole time the key is in for the "key Program" procedure. I'm also hearing a clicking noise

3 Answers


DelaneyElise

DelaneyElise 3/6/2019

(cont) from somewhere in the dash while the key is in the ON position. I did get the door locks to pop and the horn to honk the very last time I tried the "key program" procedure. Currently the battery is completely dead from so many tries. I'm going to get a battery charger tomorrow to charge back up. Any help is appreciated!

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Jimm

Jimm 3/7/2019

P0520 = Engine Oil Pressure Sensor/Switch Circuit

Potential causes of a P0520 code include:
Faulty engine oil pressure sensor
Excessive resistance in the oil pressure sensor circuit
Short in the circuit to/from the oil pressure sensor and/or PCM and/or ground
Faulty PCM (less likely)

As a vehicle owner / DIYer the first obvious thing to do is to check the oil level using the dipstick. You want to make sure there is adequate oil in the engine and the oil filter or drain plug are not leaking or anything like that. It's possible you have low or no oil pressure because you have a leak you are not aware of and the oil is gone.

Or, perhaps you just had an oil change and the place forgot to refill the oil, tighten the filter enough, there are different reasons you may have a P0520 or related codes.
Next, visually inspect the wiring and connectors at the oil pressure sending unit. Look for broken or frayed wires, burnt spots, loose or exposed wiring, etc. Make sure electrical connections are tight and not oily or contaminated, etc. Refer to a model specific repair manual for the location of the sender. *Remember codes never indicate what parts to change, rather where to begin diagnosis*.
The next step if nothing looks obvious is to use a digital volt ohm meter (DVOM) to probe the terminals at the oil pressure sensor both on the sensor itself and the associated wiring and harness. Compare to factory specs. Specifically check for shorts to ground, resistance that is not within spec (depends on your model/engine). Repair as necessary. In all likelihood the fix will be one of two things, a wiring issue that needs repair or a sensor that needs replacement.
Replacement of the PCM is more of a last resort and should only be done after proper diagnosis.

At this point - I would suspect the used PCM and its' re-programming ' at fault - but cannot determine without further testing.

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Jimm

DelaneyElise 3/7/2019

Thank you for your response! I checked the oil and the filter (which I always replace myself) and those things get checked every single week so oil level was right where it should be and the filter is pretty new. I replaced the Oil Pressure Sensor just in case and tested the wiring and those both are good. All connections have been checked and cleaned. I also replaced the Crankshaft Position Sensor for good measure and still no start and the P0520 was still there. I just replaced the PCM (cont)

Jimm

DelaneyElise 3/7/2019

(cont) and now I cant get my key to reprogram to the new PCM. That's where I'm at so far in terms of problems. I can't get the car to start at all until that key is reprogrammed. Any suggestions about that?

Jimm

Jimm 3/7/2019

First step would be follow the key reprogramming steps. Suggest to google search the procedure, or check with local repair shops in your area.

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Jimm

DelaneyElise 3/7/2019

Checked with both the shop we bought the PCM from and google and we've tried all that we could find! We can't find anywhere why our security light would not stay illuminated for the full 10 minutes that it's supposed to to reprogram. The light just shuts off after a few seconds.

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