SMU - SECTION 6E2 - UPGRADE EMISSIONS ONLY - REVISED

SUBJECT: SERVICE MANUAL UPDATE-SECTION 6E2-UPGRADE EMISSIONS ONLY- REVISED DTC 24 VEHICLE SPEED SENSOR (VSS) CIRCUIT AND REFERENCE VOLTAGE SPECIFICATION

MODELS: 1994 METRO WITH 1.0L ENGINE (VIN 6 - UPGRADE EMISSIONS)

REVISED DTC 24 VEHICLE SPEED SENSOR (VSS) CIRCUIT-INSERT FACING PAGE AND CHART.

PAGES AFFECTED: 6E2-A2-9 6E2-A2-44 6E2-A2-45 6E2-C1-6

REVISED VEHICLE SPEED SENSOR REFERENCE VOLTAGE _________________________________________________________ | 10/B10 | YEL/GRN | VEHICLE SPEED INPUT | 0-5V | |__________|___________|_______________________|________|

VEHICLE SPEED SENSOR (VSS)

THE VEHICLE SPEED SENSOR (VSS) CONSISTS OF A REED SWITCH BUILT INTO THE SPEEDOMETER HEAD. THE ENGINE CONTROL MODULE (ECM) APPLIES 5 VOLTS TO THE VSS (UPGRADE EMISSIONS*). AS THE SPEEDOMETER CABLE TURNS, THE REED SWITCH CLOSES THE CIRCUIT TO GROUND FOUR TIMES PER REVOLUTION OF THE SPEEDOMETER CABLE. AS VEHICLE SPEED INCREASES, THE FREQUENCY OF GROUND PULSES RECEIVED BY THE ECM ALSO INCREASES. THEREFORE, BY CALCULATING THE FREQUENCY OF THE GROUND PULSES, THE ECM IS CAPABLE OF DETERMINING VEHICLE SPEED.

*NOTE: VSS INPUT VOLTAGE ON THE STANDARD EMISSIONS IS 12 VOLTS.

FIGURES: 00 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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