For as far back as I can remember I have seen these codes (1000H & 1064H). I have been told not to worry about them. If I clear the codes they always come right back on first restart. What would be causing these?

 

A DTC code has the format L1234X where

L is a letter (B, C, P or U)
1234 are four digits
X is either a C or an H (sometimes both)

You need to post the ENTIRE code, as there are, for example a B0507 and a P0507 and they mean completely different things.

I'm gonna GUESS you are seeing a B1000H and a U1064H.

Be glad the B1000 is in an H status, if it was in a C status the ONLY thing to fix it would be to install a new BCM. The B1000 indicates the BCM had a problem writing to its internal EEPROM memory. Apparently it retried the operation and was successful on a retry, changing the status to an H.

The U1064 indicates the module that posted it (I'm gonna guess either the PCM or RFA) was unable to communicate with the BCM ... most likely it is trying to communicate while the BCM is trying to resolve its internal memory problem.

The car will set these two codes whenever you start it. I'm guessing there is at least one bit that is bad in the EEPROM ... and everytime you start the car that bit gets written to. Failing to write to that bit (the memory firmware would see a parity error in memory), the BCM probably flags a byte (or an even bigger chunk of memory) as bad, and re-tries the operation writing the data to some "spare" memory available for just this kind of problem. The retry is successful, but the B1000 is set. The bad news is this code will set everytime you start the car, the good news is, it doesn't matter, the computer was designed to work around the problem.

I wouldn't worry about it.

 

Sorry for not giving the complete codes - here they are...
BO-RFA U1000H & BO-RFA U1064H

 

Are you having problems with your Remote Door Lock functions (locking/unlocking) from your key fobs ????

If not, delete the codes and see if they come back .....

Those codes indicate that at some point in time the RFA was unable to communicate with the BCM to perform a function requested by a key fob.

 

Don't believe so? I only use the #1 Key Fob (as I am the only driver). I have deleted the codes several times and these two just come right back - been this way for years?

I do have to press Unlock 2-3 times to get the passenger door to unlock.

 

Here is a bulletin about the U1000 code:
All GM Vehicles Using Class 2 Communications Diagnostic Strategy for DTC U1000 or U1255 - kw BCM code EBTCM radio RIM #PIT3154 - (Sep 10, 2004)
All GM Vehicles Using Class 2 Communications Diagnostic Strategy For DTC U1000 or U1255
.

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:
DTC U1000 or U1255 set current or history, with or without other DTCs

Recommendation/Instructions:
DTC U1000 Class 2 Data Link

DTC U1255 Lost Communications

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 that 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 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 (ie: 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 setup.
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 setting 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. Since 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 complaint (ie: intermittent, erratic tachometer operation); this will probably be a better indication of the control module that is the source of the concern.

Here is the diagnostic procedure for the U1000 code:

DTC U1000 and U1255
Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation when 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. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least 1 critical parameter within about 5 seconds of beginning serial data communication, DTC U1000 or U1255 is set. The DTC will only be reported once if more than 1 critical parameter does not have a sending module identification number associated with it.

Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range.
Diagnostic trouble codes U1300, U1301 or U1305 are not set.
The module setting the DTC requires serial data communication to occur.
Conditions for Setting the DTC
At least 1 critical operating parameter has not been associated with an identification number within about 5 seconds after beginning serial data communication.

Action Taken When the DTC Sets
The module uses a default value for the missing parameter.

Conditions for Clearing the DTC
A current DTC U1000 or U1255 will clear when all critical operating parameter for the module have been associated with an identification number or at the end of the current ignition cycle.
A history DTC resets after 50 ignition switch cycles with no repeated failure.
Diagnostic Aids
When a malfunction such as an open fuse to a module occurs while modules are communicating, a current DTC is set indicating lost communication with a specific module DTC. When the modules stop communicating, ignition is turned OFF, the current Lost Communication DTC is cleared but the history DTC remains. When the modules begin to communicate again, the module with the open fuse will not be learned by the other modules so DTC U1000 or U1255 is set as current by the other modules. If the malfunction occurs when the modules are not communicating, only DTC U1000 or U1255 is set.

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

A Lost Communication with XXX DTC with a history status may indicate the cause of U1000 or U1255.

The modules which is not communicating is the likely cause of U1000 or U1255 being set. The following systems communicate on the class 2 serial data circuit:

Body Control Module (BCM)
Electronic Brake Control Module (EBCM)
Electronic Suspension Control (ESC) Module
HVAC (with CJ2)
Sensing and Diagnostic Module (SDM)
Instrument Panel Cluster (IPC)
Driver Door Module (DDM)
Passenger Door Module (PDM)
Seat Control Module (SCM) (with AAB)
Powertrain Control Module (PCM)
Radio
Remote Control Door Lock Receiver (RCDLR)
The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.

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

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

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

If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.

The module which set U1000 or U1255 is the likely cause of the malfunction.

Step
Action
Yes
No

1
Did you record any DTCs in the range of U1001-U1254 with a history status?
Go to DTC U1001-U1254
Go to Step 2

2
Turn ON the ignition with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.
Record all of the modules communicating on the class 2 serial data circuit.
Compare the list of modules which are communicating to the list given.
Does any module on the class 2 serial data circuit not communicate?
Go to Step 3
Go to Step 13

3
Test the battery positive voltage circuits and the ignition voltage circuits of the module that is not communicating for an open or a short to ground. Refer to Control Module References in Body Control System for the applicable schematic. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 9
Go to Step 4

4
Turn OFF the ignition.
Test the ground circuits of the module that is not communicating for an open. Refer to Control Module References in Body Control System for the applicable schematic. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 9
Go to Step 5

5
Disconnect both star connectors.
Inspect for poor connection at the star connectors. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 9
Go to Step 6

6
Test the class 2 serial data circuit of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 9
Go to Step 7

7
Inspect for poor connections at the battery positive voltage circuits, the ignition voltage circuits, the ground circuits, and the class 2 serial data circuit of the module that is not communicating. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 9
Go to Step 8

8

Important
Perform the set up procedure for module if required.


Replace the module which is not communicating. Refer to Control Module References in Body Control System.

Did you complete the replacement?
Go to Step 11
--

9
Install a scan tool.
Turn ON the ignition with the engine OFF.
Select the Display DTCs function for the module which was not communicating.
Does the scan tool display and DTCs which do not begin with a "U"?
Go to Control Module References in Body Control System for the applicable Diagnostic System Check
Go to Step 10

10
Use the scan tool in order to clear the DTCs.

Did you complete the action?
Go to Step 11
--

11
Select the Display DTCs function for the modules which had U1000 or U1255 set as a current DTC.

Does the scan tool display any DTCs which do not begin with a "U"?
Go to Control Module References in Body Control System for the applicable Diagnostic System Check
Go to Step 12

12
Use the scan tool in order to clear the DTCs.

Did you complete the action?
System OK
--

13
Did you record any other DTCs for the modules which had U1000 or U1255 set as a current DTC?
Go to Control Module References in Body Control System for the applicable Diagnostic System Check
Go to Step 14

14
Install a scan tool.
Turn ON the ignition with the engine OFF.
Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for at least 5 seconds.
Turn ON the ignition with the engine OFF.
Select the Display DTCs function.
Does the scan tool display U1000 or U1255 set as a current DTC?
Go to Step 15
Go to Diagnostic Aids

15

Important
Perform the set up procedure for module if required.


Replace the module which had U1000 or U1255 set as a current DTC. Refer to Control Module References in Body Control System.

Did you complete the replacement?
System OK


And now for U1064:
DIC Onboard Diagnostics Show DTCs U1016, U1064 and U1096 in History #PI00043 - (Jun 19, 2002)
DIC Onboard Diagnostics Show DTCs U1016, U1064 and U1096 in History
.

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Condition/Concern:
DTCs U1016, U1064 and U1096 may be present when scrolling through the onboard diagnostics via the instrument cluster Driver Information Center (DIC).

Recommendation/Instructions:
This is a normal software function as long as the DTCs have a history status upon ignition cycling. No repair attempts should be made.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

Hope this helps.

Bill

 

Bill and Steve

THAT'S WHY you guys are INVALUABLE to the forum! The technical stuff that you guys dig up and post is truly amazing!

Steve

The SWPS and EBTCM (EBCM ) post information that you have been posting is EXCELLENT!!

I have seen a weak battery cause some U series DTCs. Especially in my early produced 98. During cold cranking in the morning (when the weak OEM battery put out all night to keep everything alive ) the weak battery allows B+ (12 VDC) to drop too LOW. If it drops lower than the module in questions operating cut off limit, the module will drop off line for that period of time until the voltage rises above the cutoff and a history U series DTC gets set.

My 98 would set 5-6 U series DTCs when the OEM Delco was 5 years old Once I put a NEW battery in,,,NO MORE U series DTCs.

BC