Thread: Check Engine Light on - Codes included

Yeah, I say check the PCM...what year GP is it?

If it is a 2003 I have a DHP I'd sell ya

I did some checking today and the U codes are real. They are bonafide OBD-II codes. I had never seen nor tested/diagnosed a car before that showed them so I was a little tripped out by seeing them posted. I knew what others were and for, but I just had never seen any type of U code before.

P codes, such as P0300, are Powertrain Codes
B codes, such as B0269, are Body Codes
C codes, such as C0894, are Chasis Codes
U codes, such as U1305 are UART Serial Data Code

P0, B0, C0 codes are Generic OBD-II codes, where as P1, B1, C1 codes are manufacturer specific.

Now, I checked for your U1305 and could not find it even in Alldata, the highest it goes there is U1304

Dont even try to extract any information from me on U codes as I have NEVER troubleshot one and as mentioned never seen one set until you posted it here. I did find some info on your U1016, how helpful it will be, I dont know but I'll post it up.

U1016

CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring or Node Alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, the module will monitor for that module's "Node Alive" message. Each module on the class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a "Node Alive" message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx, where xxx is equal to the 3-digit identification number, is set.



The Control Module ID Number list provides a method for determining which module is not communicating. A module with an internal class 2 serial data circuit malfunction or which loses power during the current ignition cycle would have a Lost Communication DTC set by other modules. The modules that can communicate will set a DTC indicating the module that cannot communicate.

When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order:

1. Current DTCs before history DTCs unless told otherwise in the diagnostic tables
2. The DTC which is reported the most times
3. From the lowest number DTC to the highest number DTC.

CONDITIONS FOR RUNNING THE DTC

• Voltage supplied to the module is in the normal operating voltage range of 9 to 16 volts .
• Diagnostic trouble codes U1300, U1301 and U1304 do not have a current status.
• The vehicle power mode requires serial data communication to occur.

CONDITIONS FOR SETTING THE DTC
A message from a learned identification number has not been detected for the past 5 seconds .

CONDITIONS FOR CLEARING THE DTC

• A current DTC will clear when a "Node Alive" message from the failed identification number is detected on the class 2 serial data circuit or at the end of the current ignition cycle.
• A history DTC will clear after completing 100 ignition cycles with no repeated malfunction.

TEST DESCRIPTION



The numbers below refer to the step numbers on the diagnostic table.

1. A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.
2. A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.
3. The malfunction is due to an open in the class 2 serial data circuit or an open in the module.

1. The module which was not communicating may have set Lost Communication DTCs for those modules that it was monitoring.

1. The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules in order to avoid future misdiagnosis.

hahah i have some of them too 1998 regal gsx and a buddy has a 2003 gsx and some of these same codes