General Specification Electrical Function gmw3110 General Motors Local Area Network Enhanced Diagnostic Test Mode Specification

Procedure 7: 
(Valid if the Device Control security access levels of the $27 service are supported. All steps 
assume programming mode is not active)
 
1. Transmit a service $20 request to a node with a non-zero Manufacturers Enable Counter (MEC). After the 
$60 positive response, verify via a service $27 $03 request that the node becomes unlocked (seed = 
$0000). 
2. Transmit a service $20 request message to a node with the MEC = $00 and at a time when device control 
security is currently unlocked via service $27 SecurityAccess. After the $60 positive response, verify via a 
service $27 $03 request that the node is locked (seed != $0000). 
Procedure 8: 
1. While not in programming mode, transmit a service $28 request to disable normal mode communications. 
After normal communications have been halted, transmit a $20 service request message to return the 
node back to normal communications. Verify that the positive response is sent. Transmit a diagnostic 
request that should result in a diagnostic response and verify that the response is transmitted by the ECU. 
Then have the operator initiate a vehicle function, which should result in VN activation and normal 
communication. Verify that the ECU starts transmitting the appropriate normal mode message. 
Procedure 9: 
1. Invoke a diagnostic service that results in DTCs being disabled ($10, $28, or $AE). Disconnect any input 
which would normally result in a DTC being set. Verify that the DTC does not set via the $A9 service. Send 
a $20 request message and verify the positive response and that the DTC will set after the appropriate 
conditions are met to set the DTC. 
2. Repeat step 1 of this procedure for each supported service that can disable the setting of DTCs. 
8.5.8 Tester Implications. 
When sending a request for this service to terminate a high speed programming 
event on the SWCAN link, the tester shall reinitialize its CAN protocol converter hardware to low speed 
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