Last post on Sep 11, 2012 at 3:39 AM
You are in the Cadillac DeVille
What is this discussion about?
Cadillac DeVille, Lights, Electrical, Sedan
#33 of 191 Service Engine Soon Light is back on again
Apr 11, 2006 (6:13 pm)
About 4 months ago my Service Engine Soon Light came on,on my 1997 Cadillac Deville.I found out how to access the on board computer and found the trouble code,which was causing the light to come on. The trouble code was P1139,which was the oxygen sensor located behind the catalytic converter.I purchased a new sensor and installed it. After the installation,I disconnected the positive lead
to the battery and cleared the trouble code. Now after 4 months of operation and no incidents,the same code has suddenly reappeared.Now what?
#34 of 191 Re: Service Engine Soon Light is back on again [vic8]
by MrShift@Edmunds HOST
Apr 12, 2006 (8:05 am)
YOu were fooled by the code. The code doesn't identify the defective part. No onboard computer can yet do that. It just identifies the circuit with the problem. So you need to start a diagnostic "tree" on that circuit and eliminate each component in the circuit by testing. Your 02 sensor was probably stressed out by some other defective function, so putting in a new one was possibly just providing a fresh victim for the real culprit.
#35 of 191 Re: Service Engine Soon Light is back on again [Mr_Shiftright]
Apr 12, 2006 (1:55 pm)
Thank you for getting back to me.When I originally read the trouble code it pointed to the oxygen sensor,but after it finished running through all the other systems it came to the end and left me with a PCM?.Could this be that, the problem is somewhere in the PCM circuit?
Today I had a friend of mine put his code meter on and came up with the same P1139 code oxygen sensor,his meter did show another code that was not showing up on the cars computer.The code he read said #6 cylinder has miss fired.
Could this possibly be the problem,thats causing the oxygen sensor to go bad?Thanks Again!
#36 of 191 Re: Service Engine Soon Light is back on again [vic8]
by MrShift@Edmunds HOST
Apr 12, 2006 (2:29 pm)
Hmmm....tricky question, like the chicken and egg question...if the 02 sensor is bad, it can't tell the computer how to adjust the fuel mixture, so THAT could cause a misfire....but can a misfire cause a bad 02 sensor....I don't think directly, but a bad misfire could overheat the catalytic converter and THAT could eventually cause the 02 sensor to become contaminated I believe.
So the short answer....I don't know for sure. This is where thorough diagnostics comes in.
#37 of 191 Re: Service Engine Soon Light is back on again [Mr_Shiftright]
Apr 13, 2006 (11:35 am)
Thanks again for your help.I think I'm going to change the plugs,take out the new sensor I installed four months ago clean it up,put it back in, then clear the sensor code and cross my fingers,arms,legs,eyes and what ever else you can cross ha ha! Thanks again Buddy!
#38 of 191 95 DeVille just won't start
Jun 08, 2006 (4:39 pm)
This is a 95 Cadillac DeVille with the 4.9L V8 that was running well and then one morning it would not start. It will turn over strong when the key is turned but it won't fire. Pulled the fuel line just before the fuel regulator and the fuel comes out strong when turning key to start. Checked the fuses that had to do with the ignition and fuel injectors and they check good. I pulled the plastic cover off the distributor and found what looked like the coil. Checked the plug and contacts and there is no voltage to the coil when turning key to start position. I went ahead and made a guess to change out the ignition module inside the distributor housing and that did not fix it. I have checked the codes and the codes I have recorded are as follows:
Could someone give me an idea where to go from here????
Thanks in advance for any ideas.
#39 of 191 Re: 95 DeVille just won't start [camillianite]
Jun 19, 2006 (4:08 pm)
On our '91 it was the security key system. Had a broken wire going into the switch assembly. Had to read the key resistor with an ohm meter to get the value. Hooked up a set of resistors to match that value to the cable going to the computer. Works like a champ. Other fix is a complete new switch assembly, as per the dealer. The indication was the "security" light was on. Hope this is not your problem.
#40 of 191 GUYS
Jun 23, 2006 (12:53 pm)
You should look for a corroded or loose battery
Aug 20, 2006 (4:16 pm)
Hi, I drive a 94 Concourse Deville. I have replaced my map sensor 3 times in the last 2 months. The car would work fine for one to two weeks after the replacement then I would get the PO32 error code. Also after I replaced the map sensor for the first time the car would struggle getting started and has continued to have hard starts for every following map sensor I replaced. I have replaced the connector to the sensor and have gone through the Gm Diagnostic tree to the best of my abilities with no avail. The car also seems to start better on cooler less humid days. If anyone might know what is causing these problems any advice you may have would be greatly appreciated.
#42 of 191 Re: Map Sensor [jefplane]
Aug 20, 2006 (9:56 pm)
One or more leaky injectors (hot start problem).
Leaking fuel pressure regulator (cold start problem).
Or.... is it the other way around?????
Wait a minute. Is this motor a Northstar? The above info is for a Northstar.