Microprocessor Assisted Shift Indicator DIAGNOSIIC (GROUP 36, NO. 105)

Publication date: 1986-03-01
Reference number: GROUP 36, NO. 105

MICROPROCESSOR ASSISTED SHIFT INDICATOR DIAGNOSIIC

TECHNICAL SERVICE BULLETIN

Reference Number(s): GROUP 36, NO. 105, Date of Issue: March, 1986

TRANSMISSION SHAFT FAULT TRACING

Model(s): 1985-86 Volvo 240, 740, 760

Group: 36

Bulletin No.: 105

Date: March, 1986

SERVICE INFORMATION

The following information and procedures should be used when tracing faults in Volvo models with microprocessor assisted shift indicator systems.

Shift Indicator System Components

Shift Indicator Control Unit
Clutch Pedal Switch
Rear Axle Transmitter
Overdrive Relay
Dash Indicator Lamp
Battery
Ignition Switch
Ignition Coil

SYSTEM OPERATION

The control unit receives engine RPM input from terminal 1 of the ignition coil. Vehicle speed data is collected at the rear axle transmitter and sent to the control unit. The clutch pedal switch informs the control unit whenever a gear change occurs. Additional information is provided by the overdrive relay.

NOTE: If current to the control unit is interrupted for any reason (dead battery, disconnected battery, etc.), the control unit MEMORY is completely erased. The control unit must be reprogrammed before vehicle may be operated. To reprogram the control unit, drive the vehicle in each forward gear for at least 8 seconds. The dash indicator lamp will flash once as programming for each gear is accepted by the control unit.

SELF DIAGNOSIS SYSTEM

The shift indicator system is capable of self diagnosing some faults within the system, such as continuity of associated circuits. The battery must be disconnected, then reconnected to activate the diagnostic mode.

SELF DIAGNOSIS PROCEDURE

Action

Indicator Light

Test Function

Depress Clutch ⁽¹⁾

Clutch Switch & Related Circuits

Overdrive Switch ON ⁽¹⁾

⁽²⁾ Overdrive Circuit

Start Engine

Coil Input Signal

Drive Away

Turns OFF

Speed Input Signal

⁽¹⁾	Tests are performed with the ignition switch on the engine off.

⁽²⁾	Overdrive circuit test also checks relay switch and 4th gear switch.

NOTE: DO NOT use the clutch pedal as a footrest as improper system operation will occur. Proper clutch adjustment is critical to ensure proper system operation. An improperly adjusted clutch should be suspected first, whenever system faults are found.

Fig 1: Shift Indicator System