Engine Controls - Tools to Retrieve Mode 6 Data

BULLETIN NO.: 98-T-75

ISSUE DATE: December, 1998

GROUP/SEQ. NO.: General Info-01

CORPORATION NO.: 99-06-04-003

SUBJECT:
Use of Serial Data Link Diagnostic Communication Tools to Retrieve Mode 6 Data (Request On-Board Monitoring Test Results by Test ID)

MODELS AFFECTED:
All 1996-1998 Saturn Vehicles

PURPOSE:
Federal emission regulations require that a vehicle be able to display certain data when interrogated using an off-board tool. One group of data that must be displayed is Mode 6 Data. Within Mode 6 Data is a section that requests EGR flow test results. The following is a description of the EGR flow test results:

Test ID $07 Request EGR flow lest results
Comp ID $OD Request for deceleration test only
Test Value (0D) Scaling of the test value is a 2's complement
signed number: QEMDSTHR
E=(N) counts (2 byte)
Test Limit (0D) Scaling of the test value is a 2's complement
signed number: QEMDSEWN
E=(N) counts (2 byte)

On all 1996-1998 Saturn vehicles, the EGR flow test results are incorrectly displayed in the reverse order. Instead of the test results being displayed Test Value first and Test Limit second, the Test Limit is displayed first and Test Value is displayed second. This must be taken into consideration when displaying Mode 6 Data or when developing communication tools that use Mode 6 Data communication.

IMPORTANT:
The preceding information only affects off-board diagnostic communication tools that use a Mode 6 Data request. The Saturn off-board diagnostic communication tools (Tech 2, PDT, and SSS) do not use Mode 6 Data to interrogate any vehicle data.