Ok sounds good! Next time I drive the truck I will set on of my gauges to moniter voltage and make sure to check for codes if any of the lights come on again.


Thanks everyone for the help so far! Nothing seems to be wrong when it does this but iritates me that its happening.

 

Ok... So I have an update sooner then I thought I would. Went to go put gas in the truck while 93 is down to $3.49 here.

1st start up for the day and the battery voltage (using aeroforce gauge) held a steady 14.0-14.1v. Once I got moving down the road and hit the first stop light, voltage dipped to a lowest of 13.6 with AC and headlights on. But held steady at 13.8-14.0 once cruising (1500-1800rpms).

Stopped at Sunoco, filled up. Started the truck, reset my trip and went on my way. Before I even got out of town the Security light (only) came on and stayed on. Voltage still showing a steady 13.8-14.0v while driving back home. Stopped at the school by my house, pulled the codes from my gauge and shut the truck off for a couple minutes. Started it back up and the light stayed off.

Codes shown were:

P1626
U1064

 

DTC P1626

CIRCUIT DESCRIPTION
The control module communicates with other modules using the class 2 serial data circuit. The vehicle theft deterrent (VTD) body control module (BCM) sends a vehicle security password to the powertrain control module (PCM), via the class 2 serial data circuit, after the BCM has sensed the proper operation of the ignition switch and lock, and determined that the switch and lock have not been tampered with. If this password matches the password stored in the PCM, fuel will be enabled. If the BCM does not send a password, or if the PCM does not receive it, the vehicle will not start, or it may start and stall. This will set a DTC P1626 in the PCM memory. If communication is lost after receiving the password, the VTD Passlock system will go into Fail Enable, set a U1192 in the PCM memory, and the engine will continue to run. This will allow the engine to restart on future ignition cycles but may set a DTC P1626 as the engine is started. If the battery is disconnected or the codes are cleared, the vehicle will lose its Fail Enable status and will not start until communication is re-established.

DTC DESCRIPTOR

This diagnostic procedure supports the following DTC:
DTC P1626 Theft Deterrent Fuel Enable Signal Lost

CONDITIONS FOR RUNNING THE DTC

•The VTD system is enabled.
•The fuel enable decision point has been reached, or the engine is cranking.

CONDITIONS FOR SETTING THE DTC

The PCM has not established communications with the BCM and has not received a valid password before the fuel disable decision point was reached.

ACTION TAKEN WHEN THE DTC SETS

•The PCM stores the DTC in history after the first failure but will not illuminate the malfunction indicator lamp (MIL).
•The PCM records the operating conditions at the time the diagnostic fails. The PCM stores the failure information in the scan tools Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

•A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles.
•A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature (ECT) exceeds 70°C (160°F) during the same ignition cycle.
•Use the scan tool Clear Information function.

DIAGNOSTIC AIDS

IMPORTANT: Do not clear DTCs unless directed by a diagnostic procedure. Clearing DTCs will also clear valuable Freeze Frame and Failure Records data.

•Inspect for published service bulletins relating to exhibited symptoms or component operation.
•Inspect all related wiring and connections including the PCM and BCM connections. These may cause an intermittent malfunction.
•If the class 2 serial data circuit is shorted to ground or shorted to voltage, then all systems connected to the serial data circuit will not be able to communicate properly. Systems capable of storing loss of communications DTCs, or the DTCs with the letter "U" as a prefix, will have these codes stored in their memory. If a DTC U1192 is stored in the PCM memory along with the P1626, then a fault occurred at some point after the PCM received the correct password. The BCM must also be inspected for intermittent operation due to a loss of power or ground to the module itself. After repairing the cause of DTC 1626, clear all DTCs from the systems capable of storing this DTC and DTC U1192.
•The VTD Passlock parameters can be monitored in the PCM under engine data 2, display with a scan tool.
•The scan tool Diagnostic Circuit Check can be used to:
•Monitor the class 2 serial data circuit for modules which have been or are communicating.
•Monitor for loss of communications DTCs with the letter "U" as a prefix: U1001-U1199.
•Clear loss of communication DTCs. When a Clear Codes command is issued, all codes, Freeze Frame and Failure Records information is cleared.
•The scan tool Class 2 Message Monitor will show the status of each module on the class 2 circuit. A status of Active indicates that the module is communicating with the scan tool. An Inactive status indicates that the module previously communicated with the scan tool, but is not communicating currently. The inactive status will only appear if the loss of communication occurs while on the Message Monitor screen. If a module is not listed at all, then the missing module never successfully established communications with the scan tool or lost communication while on another screen. Refer to Scan Tool Does Not Communicate with Class 2 Device in Computer/Integrating Systems for the complete class 2 data link to determine if there are any unlisted modules.
•An intermittent may be caused by any of the following conditions:
•A poor connection
•Rubbed through wire insulation
•A broken wire inside the insulation
•Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint.
•If a repair is necessary,

 

DTC U1064

Loss of Communications with DIM
Refer to Data Link Connector (DLC) Schematics

Circuit Description
The class 2 serial data line communicates information between modules. Each module connected to the serial data line is assigned a recognition code, or address. This code is used in order to identify which modules are communicating. Modules communicate with each other by periodically sending state of health (SOH) messages. When the ignition switch is in RUN, each module communicating on the serial data line sends a SOH message every 2 seconds. This ensures that the system is operating properly. When the dash integration module (DIM) stops communicating on the class 2 serial data line, the SOH that is normally sent on the serial data line every 2 seconds disappears. The module, which expects to receive that message, detects the absence of the message. The module in turn sets DTC U1064 associated with the loss of SOH of the DIM.

Conditions for Setting the DTC
The module does not receive a state of health (SOH) message back from the DIM. The module retries the request 3 times, and then sets DTC U1064.
This DTC only sets if U1300 or U1301 is not current.
Action Taken When the DTC Sets
DTC U1064 is stored in the module.
The module uses the default values for the initialization data.
This DTC does not cause driver warning message to appear.

Conditions for Clearing the DTC
This DTC clears (status changes from current to history) under any of the following conditions:
The module detects a state of health message from the DIM.
At each ignition cycle.
A history DTC clears after 50 consecutive ignition cycles if the conditions for setting the DTC are no longer present.
Current and history DTCs may be cleared using a scan tool.
Diagnostic Aids
DTC U1064 does not normally represent a failure within the module.
When loss of class 2 serial data communication DTCs (DTCs with the letter U as the prefix) are stored as history DTCs, know all possible serial data DTCs set in each module before diagnosing the serial data line.
If U1064 is stored in the module memory, inspect for the same DTC stored in other modules capable of storing this DTC.
If the DTC is a history DTC, the problem may be intermittent.
Test Description
The numbers below refer to the step numbers on the diagnostic table:

U1064 is the result of loss of communication with the dash integration module (DIM). Note that other modules on the class 2 serial data line may also set U1064 if the DIM is not communicating with the serial data line.

Clear all DTCs after the repair procedure is complete.

Step
Action
Value(s)
Yes
No

1
Did you perform the Data Link Communications Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - Data Link Communications

2
Use a scan tool in order to attempt the establish communication with the dash integration module (DIM).

Does the scan tool communicate with the DIM?
--
Go to Step 3
Go to Diagnostic System Check - Body Control System in Body Control System.

3
Inspect and repair the class 2 serial data line CKT 1807 (PPL) for intermittent connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Is the repair complete?
--
Go to Step 4
--

4
Turn off the ignition switch.
Reconnect or install any connectors or components that were disconnected or removed.
Turn on the ignition switch.
Clear any DTCs.
Is the repair complete?

 

Do you have an aftermarket alarm or a remote start hooked up???

 

Hmm.... Sounds like this is going to be complicated.


Just remembered though, my cruise control module is not hooked up cause a mouse got a couple wires. But I dont think that would cause any of that?


No aftermarket alarm or remote start.

 

If there was mouse in there it could have gotten a wire for the communication and could cause this issue.

So can aftermarket electronics like alarms and remote starts

 

In fact does that Aero Force Gauge plug into DLC connector under the dash???

 

Yea they plug right in to the OBDII port. It only reads PCM stuff I believe.

I just cant remember when I first saw this happen to pin point what may have been done to cause it. But Ill have to get my buddy at the chevy dealer in town to throw a Tech 2 on it and run a diag test on the modules and see whats up. Was hoping it might be something simple but doesnt sound that way!

I HATE electrical issues!

 

There not fun. If a mouse got the wire its easy to repair. If its the not there with the gauge then something with the gauge is causing it. If you have aftermarket alarm or remote start the issue could be with that. If it's none of the above the worst case would be the body control module.