Speedometer Malfunction

METER: METER / GAUGE SYSTEM: Speedometer Malfunction
- Speedometer Malfunction

DESCRIPTION

Factors that affect the indicated vehicle speed include tire size, tire inflation, and tire wear.

The speed indicated on the speedometer has an allowable margin of error. This can be tested using a speedometer tester (calibrated chassis dynamometer). For details about testing and the margin of error, see the reference chart On-Vehicle inspection.

WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
If the vehicle speed is outside the allowable range when tested, perform the following procedure On-Vehicle inspection.

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (SPEED METER OPERATION)

(a) Connect Techstream to the DLC3.

(b) Ignition switch on (IG).

(c) Turn the tester on.

(d) Enter the following menus: Body Electrical / Combination Meter / Active Test.

(e) Check the operation by referring to the table below.

Combination Meter:





*1: U.S.A.

*2: Except U.S.A.

OK:

Needle indication is normal.

NG -- REPLACE COMBINATION METER ASSEMBLY
OK -- Continue to next step.

2. READ VALUE USING TECHSTREAM (VEHICLE SPEED METER)

(a) Connect Techstream to the DLC3.

(b) Ignition switch on (IG).

(c) Turn the tester on.

(d) Enter the following menus: Body Electrical / Combination Meter / Data List.

(e) Check the values by referring to the table below.

Combination Meter:





OK:

Vehicle speed displayed on the tester is almost the same as the actual vehicle speed displayed in Techstream.

NG -- READ VALUE USING TECHSTREAM (FR/FL/RR/RL WHEEL SPEED)

OK -- REPLACE COMBINATION METER ASSEMBLY

3. READ VALUE USING TECHSTREAM (FR/FL/RR/RL WHEEL SPEED)

(a) Connect Techstream to the DLC3.

(b) Ignition switch on (IG).

(c) Turn the tester on.

(d) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

(e) Check the values by referring to the table below.

ABS/VSC/TRAC:





OK:

Vehicle speed displayed on the tester is almost the same as the actual vehicle speed displayed in Techstream.

NG -- GO TO BRAKE CONTROL SYSTEM
OK -- Continue to next step.

4. INSPECT COMBINATION METER ASSEMBLY (OUTPUT VOLTAGE)

(a) Disconnect the A34 connector.





(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:





NG -- CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - COMBINATION METER)
OK -- Continue to next step.

5. INSPECT SKID CONTROL ECU (INPUT WAVEFORM)

(a) Check the input waveform.

(1) Remove the combination meter assembly with harness connected.

(2) Reconnect the A34 connector.

(3) Connect the oscilloscope to the terminals E30-25 (SI) and body ground.





(4) Start the engine.

(5) Check the input waveform according to the condition(s) in the table below.

OK:

The waveform is displayed as shown in the illustration.





HINT
When the system is functioning normally, one wheel revolution generates 4 pulses. As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

NG -- REPLACE SKID CONTROL ECU

OK -- REPLACE COMBINATION METER ASSEMBLY

6. CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - COMBINATION METER)

(a) Disconnect the E30 and A34 connectors.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE COMBINATION METER ASSEMBLY