SMU - SECTION 9J - REVISED SCHEMATICS, TEXT AND DTC CHART

SUBJECT: SERVICE MANUAL UPDATE - SECTION 9J - REVISED SCHEMATICS, TEXT, AND DTC CHARTS 35 AND 36 TO CORRECT THE FRONT END DISCRIMINATING SENSOR RESISTANCE VALUE

MODELS: 1996 GEO METRO

THIS BULLETIN IS BEING ISSUED TO REVISE ALL THUMBNAIL SCHEMATICS IN SECTION 9J OF THE SERVICE MANUAL (SEE FIGURE 1). THE FRONT END DISCRIMINATING SENSOR DIAGNOSTIC RESISTOR SHOULD BE 8.45 OHMS. IT ALSO UPDATES STEP 1 OF THE DTC 35 CHART ON PAGE 9J-47 AND STEP 1 OF THE DTC 36 CHART ON PAGE 9J-49 (SEE ATTACHMENTS 1 + 2).

THE FACING PAGE "CIRCUIT DESCRIPTION" FOR DTC 35 AND 36 IS ALSO UPDATED AS FOLLOWS:

DTC 35 CIRCUIT DESCRIPTION ===================

WHEN THE IGNITION SWITCH IS TURNED TO "ON", THE SDM WILL PERFORM TESTS TO DIAGNOSE CRITICAL MALFUNCTIONS WITHIN ITSELF. UPON PASSING THESE TESTS, "IGNITION 1", 23 VLR AND DEPLOYMENT LOOP VOLTAGES ARE MEASURED TO ENSURE THEY ARE WITHIN THEIR RESPECTIVE NORMAL VOLTAGE RANGES. THE SDM THEN PROCEEDS TO "CONTINUOUS MONITORING". THE SDM CONTAINS A RESISTOR NETWORK CONNECTED TO "IGNITION 1", GROUND, AND TO SDM "SENSOR SIGNAL" TERMINAL "2". THE 8.45K OHMS RESISTOR IN THE FRONT END DISCRIMINATING SENSOR PARALLEL TO THE NORMALLY OPEN SWITCH PROVIDES A PARALLEL PATH TO GROUND CAUSING A SPECIFIED PERCENTAGE OF VOLTAGE TO APPEAR AT THE SDM "SENSOR SIGNAL" INPUT. THIS VOLTAGE IS MONITORED TO DETECT SHORTS TO GROUND OR A CLOSED DISCRIMINATING SENSOR.

DTC 36 CIRCUIT DESCRIPTION ===================

WHEN THE IGNITION SWITCH IS TURNED TO "ON", THE SDM WILL PERFORM TESTS TO DIAGNOSE CRITICAL MALFUNCTIONS WITHIN ITSELF. UPON PASSING THESE TESTS, "IGNITION 1", 23 VLR AND DEPLOYMENT LOOP VOLTAGES ARE MEASURED TO ENSURE THEY ARE WITHIN THEIR RESPECTIVE NORMAL VOLTAGE RANGES. THE SDM THEN PROCEEDS TO "CONTINUOUS MONITORING". THE SDM CONTAINS A RESISTOR NETWORK CONNECTED TO "IGNITION 1", GROUND, AND TO SDM "SENSOR SIGNAL" TERMINAL "2". THE 8.45K OHMS RESISTOR IN THE FRONT END DISCRIMINATING SENSOR PARALLEL TO THE NORMALLY OPEN SWITCH PROVIDES A PARALLEL PATH TO GROUND CAUSING A SPECIFIED PERCENTAGE OF VOLTAGE TO APPEAR AT THE SDM "SENSOR SIGNAL" INPUT. THIS VOLTAGE IS MONITORED TO DETECT SHORTS TO VOLTAGE OR AN OPEN DISCRIMINATING SENSOR CIRCUIT.

FIGURES: 01 ATTACHMENTS: 02

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.

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