Scan tool powers up but no link - 2001 Chevrolet Silverado 3500

Check
Instrument Panel Fuse Box ?2

Radio and Radio Amplifier

Fuse Box Diagram Chevrolet Impala (2000-2005)

https://fuse-box.info > chevrolet > chevrolet-impala-20...
Fuse box location. It is located on the passenger's side of the instrument panel, behind the cover.

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Serial Data Control of Retained Accessory Power (RAP)
Retained accessory power (RAP) is a vehicle power mode that permits the operation of selected customer convenience items after the ignition switch is turned OFF. These selected items will remain in operation until a passenger compartment door is opened or until the RAP function timer reaches its shut-off limit.
The class 2 RAP power mode is mapped to GMLAN serial data circuit as Off power mode. Refer to Data Link Communications Description and Operation for more information on data link communications. The body control module (BCM) monitors the ignition mode signal from the ignition mode switch, battery condition and the doors status to determine whether RAP should be initiated. The modules that support the RAP power mode will operate the systems under their control as required by their RAP power mode strategy.
RAP will end when one of the following conditions is met:
• The BCM detects the opening of a passenger compartment door.
• The RAP timer expires.
• The battery capacity decreases below a prescribed limit.
• Any other ignition switch state is chosen.
The functions supported in the RAP power mode are:
• The power windows
• The instrument panel cluster (IPC) and driver information center (DIC) displays
• The entertainment devices

Retained Accessory Power (RAP) On After Timeout

Step
Action
Yes
No
Schematic Reference: Data Link Connector Schematics
Connector End View Reference: Master Electrical Component List in Wiring Systems
1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
On the scan tool select Data Link Tests under Computer/Integrating Systems, and then Class 2 Power Mode.
Close all the doors.
Turn ON the ignition, with the engine OFF.
Wait 5 seconds, then turn the ignition OFF.
Wait approximately 10 minutes.
Did the scan tool display the RAP power mode and after 10 minutes the OFF-Awake power mode?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
With the scan tool observe the driver and passenger door ajar switches.
Open and close each door.
Does the scan tool display change from Door Ajar to Door Closed?
Go to Step 4
Go to Symptoms - Doors in Doors
4
With the scan tool observe the driver and passenger door open switches.
Open and close each door.
Does the scan tool display change from Door Open to Door Closed?
Go to Step 5
Go to Symptoms - Doors in Doors
5
Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?
Go to Step 6
--
6
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 1

Did you check for BCM codes
DTC B1477
Retained Accessory Power Circuit Low
DTC B1478
Retained Accessory Power Circuit High
DTC B1397
Device Voltage Reference Out #1 CKT Low
DTC B1398
Device Voltage Reference Out #1 CKT High
Charging system check ?

Diagnostic System Check - Retained Accessory Power
Test Description
The numbers below refer to the step numbers on the diagnostic table.

1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.


2. This step is checking for DTCs in the BCM.


3. This step is checking for RAP specific DTCs.

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?
Go to Step 2
Go to Scan Tool Does Not Power Up in Data Link Communications

2

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with the body control module.

Does the scan tool communicate with the BCM?
Go to Step 3
Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

3

Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
2. Rotate the ignition switch through all positions while observing the Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control Systems, for a list of the power mode states that correspond to each ignition switch position.

Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions?
Go to Step 4
Go to Power Mode Mismatch in Body Control System

4

Select the BCM display DTCs function on the scan tool.

Does the scan tool display any DTCs?
Go to Step 5
Go to the Symptoms list in the appropriate service category

5

Does the scan tool display B1477 or B1478?
Go to Diagnostic Trouble Code (DTC) List
Go to Symptoms - Retained Accessory Power

Is check engine light Lit ? You should have all the computers on the vehicle check for DTC'S - diagnostic trouble codes ! Check the battery an all connections !
Diagnostic Starting Point - Engine Electrical
Begin the system diagnosis with the Diagnostic System Check - Engine Electrical . The Diagnostic System Check will provide the following information:
?€¢
The identification of the control module(s) which command the system.

?€¢
The ability of the control modules to communicate through the serial data circuit.

?€¢
The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.
Diagnostic System Check - Engine Electrical
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
The symptom list in Symptoms will determine the correct diagnostic procedure to use.
The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
Step
Action
Yes
No

1
Did you perform the Battery Inspection/Test?
Go to Step 2
Go to Battery Inspection/Test

2
Install a scan tool.
Does the scan tool power up?
Go to Step 4
Go to Scan Tool Does Not Power Up in Data Link Communications

3
Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.
Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
Rotate the ignition switch through all positions while observing the Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control System for a list of the power mode states that correspond to each ignition switch position.
Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions?
Go to Step 4
Go to Power Mode Mismatch in Body Control System

4
Turn ON the ignition, with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit:
• The body control module (BCM)
• The driver information center (DIC)
• The instrument panel cluster (IPC)
• The powertrain control module (PCM)
Does the scan tool communicate with any module on the class 2 serial data circuit?
Go to Step 5
Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

5
Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules have DTCs set.
Record all of the displayed DTCs the DTC status and the module which set the DTC.
Does the scan tool display any DTCs?
Go to Step 6
Go to Symptoms - Engine Electrical

6
Does the scan tool display any DTC beginning with "U"?
Go to Diagnostic Trouble Code (DTC) List in Data Link Communications
Go to Step 7

7
Does the scan tool display any DTC beginning with "B"?
Go to Diagnostic Trouble Code (DTC) List in Body Control Systems
Go to Diagnostic Trouble Code (DTC)

This is the way you start diagnosing this system !
Automatic Level Control Diagnostic System Check
Install a scan tool. Does the scan tool power up?
Go to Step 2
Go to Scan Tool Does Not Power Up in Data Link Communications

2

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with the Rear Integrated Module (RIM).

Does the scan tool communicate with the RIM?
Go to Step 3
Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
Select the automatic level control display DTC function on the scan tool.
Does the scan tool display any DTCs?
Go to Step 4
Go to Symptoms

4
Does the scan tool display any DTCs which begin with a "U"?
Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Connector Diagnosis
Go to Step 5

5

Does the scan tool display DTC B1007 or B1009?
Go to Diagnostic Trouble Code (DTC) List/Type in Body Control System
Go to Step 6

6

Does the scan tool display DTC B1327?
Go to Diagnostic Trouble Code (DTC) List/Type in Engine Electrical
Go to Diagnostic Trouble Code (DTC) List/Type
This is one you should take to a ASE certified repair facility , there are electronic modules involved you have no idea about !

Some generic scan tools do not do "ALL" cars. is your unit specific to your car? It also sounds like the vehicles' main computer might be bust. Get it checked by a properly qualified and licensed Mechanic.

I hope my suggestions can help you ,first ,you can check the storage of battery and the engine ,if there is no power to use , second , check if the power is connected well .

The protocol is class 2 . Maybe your code reader is no good .
012 GM Class II Communications

Data Link Connector (DLC)
The data link connector (DLC) contains the following serial data links:
• Class II
• Entertainment and Comfort (E&C)
The DLC also provides a power source for the scan tool as follows:
• Unswitched voltage (B+) at DLC terminal 16 (circuit 1450)
• Ground at terminal 4 (circuit 1450) and terminal 5 (circuit 1550)

Class II Serial Data Link
The class II serial data link allows the following modules to communicate data with each other:
• Body control module (BCM)
• Electronic brake traction control module (EBTCM)
• Heater-A/C control (if equipped with RPO CJ2)
• Instrument panel cluster (IPC)
• Powertrain control module (PCM)
• Inflatable Restraint Sensing and Diagnostic Module (SDM).
The Class II serial data link allows a Scan Tool scan tool to communicate with the above modules for diagnostic and testing purposes. The Class II serial data link is located at the DLC connector terminal 2. Terminal 2 consists of the following circuits:
• Circuit 1036
• Circuit 1037
• Circuit 1128
• Circuit 1049
• Circuit 1122
• Circuit 1132
Entertainment and Comfort (E&C) Serial Data Link
The entertainment and comfort (E&C) serial data link allows a scan tool to communicate with the radio or the mobile telephone handset the remote CD player (if equipped). This communication is for diagnostic and testing purposes. The E&C serial data link is located at the DLC connector terminal 14, circuit 835.
PIN #9 goes to the air bag module .

with key on ck dlc connector for power and ground if ok ecm will have to be replaced.

your underhood fuse block contains a fuse for the cigar lighter. this also powers the scan tool make sure it is not blown. chk pin 5 at data link connector for good ground pin 2 for power