: Clueless N* owners with 4 codes

06-21-04, 06:29 PM
I myself have a caddy with a 4.5 but my parents have a 99 N* with 65k. I ran the OBD for them and found the following codes.

P0440 Evaporative Emission System EVAP
P1527 Tranny Range to Pressure Switch Correlation
P 1632 Theft Deterrent Fuel Disable Signal Received
U1255 Class 2 Communication Malfunction (Serial Data Line Malfunction)

I have never really read up on the N* engine cuz well, I dont drive one. The PCM code P1632 is the only one that I may have a clue on. Twice the car has failed to start and some sort of "Theft...." message came up on the dash, and then counted down from 30 minutes to when the car could be started.

The other 3 codes I really have got no idea.:hmm:

I think within the week I will be running down to Advance to pick up the Haynes for both mine and my parents cars.

Im just hoping that someone could simply point me in the right direction or give some insight on these codes. Any help would be greatly appreciated.

06-21-04, 09:08 PM
Forget the Haynes manuals unless you need toilet paper. Find the Helms manuals on e-bay or order direct from Helms.

The P0440 code could be as simple as a gas tank cap problem.

Try clearing all the codes and see what returns after a day or two of normal driving. The code display is a great feature, but -- if the Service Engine lamp is not triggered, there is not a driveablity or emissions issue present.

06-21-04, 09:26 PM
The first thing I (and everyone else) will tell you is don't waste your money on a Haynes or Chilton manual (they are too stiff to use as toilet paper). The factory (Helm) manual is the only way to go. A bit pricey if you buy them new (try ebay) but worth every penny.
Regarding the 1632, check the key. If the contacts on the pellet are dirty (not too likely) or worn down flush with the "pellet" (again not too likely I would think on a '99) they may not make contact and will set a code and "no start wait 3 min".
The other codes will take a factory manual to chase down through the "chase around chart".
By the way, the 1255 may have set the rest of the codes. If they are history codes, clear 'em and ignore 'em until they return.

06-22-04, 01:36 AM
tighten the gas cap, clear codes, drive it. see what happens. likely simple.

06-22-04, 01:39 AM
there is no "pellet" on a 99 its either a vatsII or a transponder system. take it to a reputable shop. not necesscarily a cadillac dealer.

06-22-04, 03:04 AM
about the transponder, i think it is highly unlikely that this is a problem. the keys appear to be brand new.

today i asked my mom if she had ever had any gas cap troubles and she told me about a month ago she pumped her gas, tightened the cap and went to open her door. when she did, the little lid covering the cap popped back open. so she went back and shut it, opened the door and it popped open again. so she opened it up, and tightened the gas cap and told me "it turned another click" then she was able to open her door without anything opening.

i assume this is where the theft deterrent code came from, cuz along with the other 3 this has been history for a few weeks since i first ran the OBD

tomorrow afternoon im going to clear the codes and see if any new ones come back in the next day or so.

thank you guys for your input

06-22-04, 09:34 PM
Hmm, Didn't know that. Sorry for the misinformation.

there is no "pellet" on a 99 its either a vatsII or a transponder system. take it to a reputable shop. not necesscarily a cadillac dealer.

06-23-04, 08:29 PM
The P0440 ( "Check Gas Cap" on the DIC ) has been coming up on my '99 Deville recently (it actually appeared about a year ago, then went away). I got a replacement cap at my local Advance Auto parts, but to no avail. So it would appear that there is some other fault triggering the "Check Gas Cap" message, and if I remember from the manuals, it has something to do with the emissions/evap control system. Perhaps a loose/leaky hose back into the tank or something. The experts here (e.g. BBob and his ilk) will perhaps have more authoritative responses to offer.....


06-20-05, 07:40 AM
Found this when trying to figure out whet the u 1255 code was for my car:

This information applies to all GM vehicles Using Class 2 communication.

DTC U1000 or U1255 may set current or history, with or without other DTCs.

These DTCs set when the control module does not receive a message that it was expecting from another control module, and does not know which control module did not send the message.

If the DTC U1000 or U1255 is set in history with other DTCs set current or history, diagnose the other DTCs first.
If the DTC U1000 or U1255 is set current, this usually indicates a module that is currently not communicating or a configuration issue. For example, if the control module is configured for an option (i.e., OnStar, keyless entry, memory mirrors, etc.) that the vehicle does not have, it may expect to receive a message regarding this missing feature. This would usually occur due to the control module being recently replaced and incorrectly set up.
When the DTC U1000 or U1255 is current, the module that is not communicating may not even be listed on the Tech 2 on the Diagnostic Circuit Check /Class 2 Message Monitor list.
If the DTC U1000 or U1255 has set in history without other DTCs, replacing the control module that set the DTC is most likely NOT the solution. The module that has set the code is looking for an input from another module that is not communicating. Because the module did not receive an input that it is expecting to see, it sets a U1000 or U1255 which indicates there was a loss of communications. Look at the customer's concern (i.e., intermittent, erratic tachometer operation). This will probably be a better indication of the control module that is the source of the concern.