: 1999 Deville trouble codes



imaddicted2u
07-09-05, 10:43 PM
I have the following codes showing on my 1999 Deville:

P0440 - Evaporative Emission (EVAP) System
P1189 - Engine Oil Pressure (EOP) Switch Circuit
U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)

Can someone give me an idea where I should start looking to get rid of them?
thanks in advance.

Ranger
07-10-05, 10:51 AM
The EVAP solenoid is located on the rear cam cover (drivers side). Check the electrical connections as well as all the vacuum hoses. Also be sure the gas cap is tight.

The EOP switch is located near the oil filter adapter I believe. Make sure the connector is clean and tight. Otherwise you might need to R & R the switch.

Don't know much about U1255.

imaddicted2u
07-10-05, 08:50 PM
I did as you suggested and then I cleared the codes and they haven't returned as of yet.
Thanks Ranger

mcowden
07-11-05, 12:08 PM
Ranger is right as usual. If the codes said HISTORY, then the problem happened in the past anyway, so they probably won't come back. If they say CURRENT, then the problem is happening at that moment and clearing them wouldn't make them go away for good. If you drive the car for a while and they come back, you'll need to look a little further into the EVAP and EOP systems. Just FYI.

imaddicted2u
07-14-05, 02:17 PM
Well the code - P0440 - Evaporative Emission (EVAP) System - came back. I pulled the plug on the EVAP solenoid and got another code regarding the loss of the coil. I plugged it back in and that code moved to history. I have vacuum in to the solenoid and vacuum at the schrader valve test port. What else could be wrong. it appears as though the solenoid is good. Also a while after this code comes up I'm told to check the gas cap.

mcowden
07-14-05, 03:07 PM
Well the code - P0440 - Evaporative Emission (EVAP) System - came back. I pulled the plug on the EVAP solenoid and got another code regarding the loss of the coil. I plugged it back in and that code moved to history. I have vacuum in to the solenoid and vacuum at the schrader valve test port. What else could be wrong. it appears as though the solenoid is good. Also a while after this code comes up I'm told to check the gas cap.

Checking the gas cap is a good test. If it's bad or loose, the pressure in the tank will not be what it's expecting and that will set the code.

Presence of vacuum doesn't necessarily indicate the solenoid is good. It's possible it should be blocking vacuum but the solenoid isn't responding properly. I've had to take them out and test them with a 12VDC source. If it's getting 12VDC and it doesn't click, the solenoid is bad. The code might just be telling you that the circuit is open. The circuit might not be open if the solenoid is intact but not working properly because it's stuck. When I've replaced those things, they've been rusty and just stuck in one position. There may also be more than one solenoid to check. Where was the one you disconnected? Which code came up when you did that?

imaddicted2u
07-14-05, 05:41 PM
When I pull the plug on the solenoid the vacuum at the outlet stops, when I replug it it sucks again. The amount of suction pulsates though. Should the vacuum be steady?

mcowden
07-14-05, 10:23 PM
If the valve closes when you disconnect the solenoid, the solenoid is obviously working. I don't know for sure if the vacuum should pulsate, but I have heard that before. Maybe someone else who knows more about the evaporative emissions system will chime in here with more information.

Have you checked for leaky hoses and that the gas tank filler neck is intact and with no holes? I'm running out of ideas. Maybe the canister is cracked? Are you sure the gas cap is working right?