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ggrote1, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 16873
Experience:  26 year GM master tech
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2003 Cadillac CTS 6 Cyl. Got code p0306, and p0300. Engine

Customer Question

2003 Cadillac CTS 6 Cyl. Got code p0306, and p0300. Engine running rough of course. Later running rough and got same codes plus one for "crank shaft position sensor". Replaced Crank Shaft position sensor, reset computer ran fine with no misses. Next start up got p0306 again and p0300. Also got C112B of which I can't find any definition for. Pulled coil packs and found oil in plug cavity of Cylinder 6. Assumed oil was causing short. Replaced valve cover gaskets on both sides, installed new plugs. Reset computer, car ran fine then got p0300, and p0305, misfire cylinder 5. Stopped car, re started and ran smooth with no misfires but I'm assuming the next drive will indicate misfires in cyl 5
JA: Does the vehicle stall at low speeds? Does it sputter?
Customer: Doesn't stall but sputters, misses
JA: What is the make/model of your car?
Customer: 2003 Cadillac CTS 6 cyl
JA: Are you fixing your CTS yourself? What have you tried so far?
Customer: replaced crank shaft position sensor. replace valve cover gaskets and plugs on both sides
JA: Anything else you want the mechanic to know before I connect you?
Customer: What is code C112B ?
Submitted: 9 months ago.
Category: Cadillac
Expert:  ggrote1 replied 9 months ago.

Welcome! My name is ***** ***** I will do my best to assist you with this problem.

Expert:  ggrote1 replied 9 months ago.

that C112B is not any codes we list it maybe just a code the scan tool is picking up on that is not important to our issue

if you drive it again will it be cylinder 5 again and you will feel it skip when it acts up /.

Customer: replied 9 months ago.
I assume so, it was cyl 5 when I returned to my home and put the scanner on. Prior to my attempted fixes it was cyl6. Now the scan is showing 5
Expert:  ggrote1 replied 9 months ago.

if its # 5 again swap 5 coil with 3 coil will it still show 5 skipping ?

Customer: replied 9 months ago.
Don't understand why it would run smoothly after a computer reset or erasing the codes, and then the check eng light comes on and engine begins missing. Thought I had it fixed after discovering oil in the plug area of cyl 6 and replaced valve cover gaskets and new plugs.
Expert:  ggrote1 replied 9 months ago.

try that and see if the skip moves cylinders or not

Customer: replied 9 months ago.
can't swap coils that way, they are 3 in one coil for each bank
Expert:  ggrote1 replied 9 months ago.

i mean swap the coil banks

Customer: replied 9 months ago.
Ok, will do that Tomorrow or on Monday, can't do today. Strange that it wasn't showing Cyl 5 before the fix, but now it is showing 5, and not the original code for cyl 6
Expert:  ggrote1 replied 9 months ago.

if it does not change then be sure the coil and injector connector terminals are all good if it still acts up try some injector cleaner if it still acts up again then we have a coil issue usually

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