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

9.1.1 Enabling Diagnostic Responses on SPS_TYPE_C ECUs. 
An SPS_TYPE_C ECU shall not send 
positive or negative response messages for any diagnostic service until the programming tool enables them. 
While diagnostic responses are disabled, the ECU shall only process (but not respond to) diagnostic requests 
sent using the AllNodes request CANId and AllNodes extended address. Diagnostic responses shall become 
enabled once the ECU receives a DisableNormalCommunication ($28) request followed by a 
ReportProgrammedState ($A2) request. The SPS_TYPE_C ECU shall only respond to the $A2 request during 
this sequence, and shall respond to all subsequent diagnostic requests until a TesterPresent timeout occurs or 
a ReturnToNormalMode ($20) request is received. 
Once an SPS_TYPE_C ECU has enabled diagnostic responses, it shall enable two special-case diagnostic 
CAN Identifiers for programming purposes. The special case CAN Identifiers are defined as: 

SPS_PrimeReq CANId = $0xx, where xx represents the ECU diagnostic address value. This CANId shall 
be used as the point-to-point (PTP) request CANId. 

SPS_PrimeRsp CANId = $3xx, where xx represents the ECU diagnostic address value. This CANId shall 
be used as the USDT response CANId. 
During the sequence to enable diagnostic responses, the SPS_TYPE_C ECU shall respond to the $A2 request 
using the SPS_PrimeRsp ($3xx) CANId. 
Diagnostic CAN Identifiers and normal mode message CAN Identifiers for a fully programmed ECU are part of 
the calibration data downloaded to the ECU during a programming event. Upon completion of a software reset, 
the now completely programmed ECU(s) shall recognize their specific CANId assignments for normal and 
diagnostic messaging. 
9.1.2 Information Contained Within The Utility File. 
A utility file is used to provide ECU step-by-step 
programming instructions to a programming tool. The utility file concept was developed to keep the 
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