Cadillac Seville / Cadillac Eldorado Forum Discussion, IPC U1255 code? in Past Cadillac Vehicle Discussion; My 98 eldo with 53K on the clock has been jerking while stopped almost like it is hesitating. I changed ...
My 98 eldo with 53K on the clock has been jerking while stopped almost like it is hesitating. I changed the plugs, wires, fpr, and nothing. I have posted this before but never got a code until now. I got an IPC U1255 History code-Class 2 Communication Malfunction and no other codes. How am I supposed to determine which module sent the code?
Found this when trying to figure out what the 1255 code was:
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.
Automobile(s): 07 Black Raven CTS, 07 Gold Mist CTS
Re: IPC U1255 code?
Under Diagnostic Aids for DTC U1255 Serial Data Line Class 2 Init. Error in the 98 Eldo shop manual- This DTC cannot be rertrieved with a current status. Diagnosis of a current U1255 is accomplished via the symtom, Scan Tool will not Communicate with the Class 2 serial data line...An intermittent condition is likely to be caused by a short to ground on the Class 2 serial data line.
The other section on U1255 basically states that: one of the modules that is requesting initialization data from another module is not being acknowleged within 5 secs, and the DTC sets. DTC U1255 Serial Data line Malfunction is located on 8-457 in the Wiring Systems section of Body and Accessories in the Eldo shop manual and on 9-106 in the Restraints section of SIR.